/*
** 2011-07-09
**
** The author disclaims copyright to this source code. In place of
** a legal notice, here is a blessing:
**
** May you do good and not evil.
** May you find forgiveness for yourself and forgive others.
** May you share freely, never taking more than you give.
**
*************************************************************************
** This file contains code for the VdbeSorter object, used in concert with
** a VdbeCursor to sort large numbers of keys for CREATE INDEX statements
** or by SELECT statements with ORDER BY clauses that cannot be satisfied
** using indexes and without LIMIT clauses.
**
** The VdbeSorter object implements a multi-threaded external merge sort
** algorithm that is efficient even if the number of elements being sorted
** exceeds the available memory.
**
** Here is the (internal, non-API) interface between this module and the
** rest of the SQLite system:
**
** sqlite3VdbeSorterInit() Create a new VdbeSorter object.
**
** sqlite3VdbeSorterWrite() Add a single new row to the VdbeSorter
** object. The row is a binary blob in the
** OP_MakeRecord format that contains both
** the ORDER BY key columns and result columns
** in the case of a SELECT w/ ORDER BY, or
** the complete record for an index entry
** in the case of a CREATE INDEX.
**
** sqlite3VdbeSorterRewind() Sort all content previously added.
** Position the read cursor on the
** first sorted element.
**
** sqlite3VdbeSorterNext() Advance the read cursor to the next sorted
** element.
**
** sqlite3VdbeSorterRowkey() Return the complete binary blob for the
** row currently under the read cursor.
**
** sqlite3VdbeSorterCompare() Compare the binary blob for the row
** currently under the read cursor against
** another binary blob X and report if
** X is strictly less than the read cursor.
** Used to enforce uniqueness in a
** CREATE UNIQUE INDEX statement.
**
** sqlite3VdbeSorterClose() Close the VdbeSorter object and reclaim
** all resources.
**
** sqlite3VdbeSorterReset() Refurbish the VdbeSorter for reuse. This
** is like Close() followed by Init() only
** much faster.
**
** The interfaces above must be called in a particular order. Write() can
** only occur in between Init()/Reset() and Rewind(). Next(), Rowkey(), and
** Compare() can only occur in between Rewind() and Close()/Reset(). i.e.
**
** Init()
** for each record: Write()
** Rewind()
** Rowkey()/Compare()
** Next()
** Close()
**
** Algorithm:
**
** Records passed to the sorter via calls to Write() are initially held
** unsorted in main memory. Assuming the amount of memory used never exceeds
** a threshold, when Rewind() is called the set of records is sorted using
** an in-memory merge sort. In this case, no temporary files are required
** and subsequent calls to Rowkey(), Next() and Compare() read records
** directly from main memory.
**
** If the amount of space used to store records in main memory exceeds the
** threshold, then the set of records currently in memory are sorted and
** written to a temporary file in "Packed Memory Array" (PMA) format.
** A PMA created at this point is known as a "level-0 PMA". Higher levels
** of PMAs may be created by merging existing PMAs together - for example
** merging two or more level-0 PMAs together creates a level-1 PMA.
**
** The threshold for the amount of main memory to use before flushing
** records to a PMA is roughly the same as the limit configured for the
** page-cache of the main database. Specifically, the threshold is set to
** the value returned by "PRAGMA main.page_size" multipled by
** that returned by "PRAGMA main.cache_size", in bytes.
**
** If the sorter is running in single-threaded mode, then all PMAs generated
** are appended to a single temporary file. Or, if the sorter is running in
** multi-threaded mode then up to (N+1) temporary files may be opened, where
** N is the configured number of worker threads. In this case, instead of
** sorting the records and writing the PMA to a temporary file itself, the
** calling thread usually launches a worker thread to do so. Except, if
** there are already N worker threads running, the main thread does the work
** itself.
**
** The sorter is running in multi-threaded mode if (a) the library was built
** with pre-processor symbol SQLITE_MAX_WORKER_THREADS set to a value greater
** than zero, and (b) worker threads have been enabled at runtime by calling
** "PRAGMA threads=N" with some value of N greater than 0.
**
** When Rewind() is called, any data remaining in memory is flushed to a
** final PMA. So at this point the data is stored in some number of sorted
** PMAs within temporary files on disk.
**
** If there are fewer than SORTER_MAX_MERGE_COUNT PMAs in total and the
** sorter is running in single-threaded mode, then these PMAs are merged
** incrementally as keys are retreived from the sorter by the VDBE. The
** MergeEngine object, described in further detail below, performs this
** merge.
**
** Or, if running in multi-threaded mode, then a background thread is
** launched to merge the existing PMAs. Once the background thread has
** merged T bytes of data into a single sorted PMA, the main thread
** begins reading keys from that PMA while the background thread proceeds
** with merging the next T bytes of data. And so on.
**
** Parameter T is set to half the value of the memory threshold used
** by Write() above to determine when to create a new PMA.
**
** If there are more than SORTER_MAX_MERGE_COUNT PMAs in total when
** Rewind() is called, then a hierarchy of incremental-merges is used.
** First, T bytes of data from the first SORTER_MAX_MERGE_COUNT PMAs on
** disk are merged together. Then T bytes of data from the second set, and
** so on, such that no operation ever merges more than SORTER_MAX_MERGE_COUNT
** PMAs at a time. This done is to improve locality.
**
** If running in multi-threaded mode and there are more than
** SORTER_MAX_MERGE_COUNT PMAs on disk when Rewind() is called, then more
** than one background thread may be created. Specifically, there may be
** one background thread for each temporary file on disk, and one background
** thread to merge the output of each of the others to a single PMA for
** the main thread to read from.
*/
#include "sqliteInt.h"
#include "vdbeInt.h"
/*
** If SQLITE_DEBUG_SORTER_THREADS is defined, this module outputs various
** messages to stderr that may be helpful in understanding the performance
** characteristics of the sorter in multi-threaded mode.
*/
#if 0
# define SQLITE_DEBUG_SORTER_THREADS 1
#endif
/*
** Hard-coded maximum amount of data to accumulate in memory before flushing
** to a level 0 PMA. The purpose of this limit is to prevent various integer
** overflows. 512MiB.
*/
#define SQLITE_MAX_PMASZ (1<<29)
/*
** Private objects used by the sorter
*/
typedef struct MergeEngine MergeEngine; /* Merge PMAs together */
typedef struct PmaReader PmaReader; /* Incrementally read one PMA */
typedef struct PmaWriter PmaWriter; /* Incrementally write one PMA */
typedef struct SorterRecord SorterRecord; /* A record being sorted */
typedef struct SortSubtask SortSubtask; /* A sub-task in the sort process */
typedef struct SorterFile SorterFile; /* Temporary file object wrapper */
typedef struct SorterList SorterList; /* In-memory list of records */
typedef struct IncrMerger IncrMerger; /* Read & merge multiple PMAs */
/*
** A container for a temp file handle and the current amount of data
** stored in the file.
*/
struct SorterFile {
sqlite3_file *pFd; /* File handle */
i64 iEof; /* Bytes of data stored in pFd */
};
/*
** An in-memory list of objects to be sorted.
**
** If aMemory==0 then each object is allocated separately and the objects
** are connected using SorterRecord.u.pNext. If aMemory!=0 then all objects
** are stored in the aMemory[] bulk memory, one right after the other, and
** are connected using SorterRecord.u.iNext.
*/
struct SorterList {
SorterRecord *pList; /* Linked list of records */
u8 *aMemory; /* If non-NULL, bulk memory to hold pList */
int szPMA; /* Size of pList as PMA in bytes */
};
/*
** The MergeEngine object is used to combine two or more smaller PMAs into
** one big PMA using a merge operation. Separate PMAs all need to be
** combined into one big PMA in order to be able to step through the sorted
** records in order.
**
** The aReadr[] array contains a PmaReader object for each of the PMAs being
** merged. An aReadr[] object either points to a valid key or else is at EOF.
** ("EOF" means "End Of File". When aReadr[] is at EOF there is no more data.)
** For the purposes of the paragraphs below, we assume that the array is
** actually N elements in size, where N is the smallest power of 2 greater
** to or equal to the number of PMAs being merged. The extra aReadr[] elements
** are treated as if they are empty (always at EOF).
**
** The aTree[] array is also N elements in size. The value of N is stored in
** the MergeEngine.nTree variable.
**
** The final (N/2) elements of aTree[] contain the results of comparing
** pairs of PMA keys together. Element i contains the result of
** comparing aReadr[2*i-N] and aReadr[2*i-N+1]. Whichever key is smaller, the
** aTree element is set to the index of it.
**
** For the purposes of this comparison, EOF is considered greater than any
** other key value. If the keys are equal (only possible with two EOF
** values), it doesn't matter which index is stored.
**
** The (N/4) elements of aTree[] that precede the final (N/2) described
** above contains the index of the smallest of each block of 4 PmaReaders
** And so on. So that aTree[1] contains the index of the PmaReader that
** currently points to the smallest key value. aTree[0] is unused.
**
** Example:
**
** aReadr[0] -> Banana
** aReadr[1] -> Feijoa
** aReadr[2] -> Elderberry
** aReadr[3] -> Currant
** aReadr[4] -> Grapefruit
** aReadr[5] -> Apple
** aReadr[6] -> Durian
** aReadr[7] -> EOF
**
** aTree[] = { X, 5 0, 5 0, 3, 5, 6 }
**
** The current element is "Apple" (the value of the key indicated by
** PmaReader 5). When the Next() operation is invoked, PmaReader 5 will
** be advanced to the next key in its segment. Say the next key is
** "Eggplant":
**
** aReadr[5] -> Eggplant
**
** The contents of aTree[] are updated first by comparing the new PmaReader
** 5 key to the current key of PmaReader 4 (still "Grapefruit"). The PmaReader
** 5 value is still smaller, so aTree[6] is set to 5. And so on up the tree.
** The value of PmaReader 6 - "Durian" - is now smaller than that of PmaReader
** 5, so aTree[3] is set to 6. Key 0 is smaller than key 6 (Banana<Durian),
** so the value written into element 1 of the array is 0. As follows:
**
** aTree[] = { X, 0 0, 6 0, 3, 5, 6 }
**
** In other words, each time we advance to the next sorter element, log2(N)
** key comparison operations are required, where N is the number of segments
** being merged (rounded up to the next power of 2).
*/
struct MergeEngine {
int nTree; /* Used size of aTree/aReadr (power of 2) */
SortSubtask *pTask; /* Used by this thread only */
int *aTree; /* Current state of incremental merge */
PmaReader *aReadr; /* Array of PmaReaders to merge data from */
};
/*
** This object represents a single thread of control in a sort operation.
** Exactly VdbeSorter.nTask instances of this object are allocated
** as part of each VdbeSorter object. Instances are never allocated any
** other way. VdbeSorter.nTask is set to the number of worker threads allowed
** (see SQLITE_CONFIG_WORKER_THREADS) plus one (the main thread). Thus for
** single-threaded operation, there is exactly one instance of this object
** and for multi-threaded operation there are two or more instances.
**
** Essentially, this structure contains all those fields of the VdbeSorter
** structure for which each thread requires a separate instance. For example,
** each thread requries its own UnpackedRecord object to unpack records in
** as part of comparison operations.
**
** Before a background thread is launched, variable bDone is set to 0. Then,
** right before it exits, the thread itself sets bDone to 1. This is used for
** two purposes:
**
** 1. When flushing the contents of memory to a level-0 PMA on disk, to
** attempt to select a SortSubtask for which there is not already an
** active background thread (since doing so causes the main thread
** to block until it finishes).
**
** 2. If SQLITE_DEBUG_SORTER_THREADS is defined, to determine if a call
** to sqlite3ThreadJoin() is likely to block. Cases that are likely to
** block provoke debugging output.
**
** In both cases, the effects of the main thread seeing (bDone==0) even
** after the thread has finished are not dire. So we don't worry about
** memory barriers and such here.
*/
typedef int (*SorterCompare)(SortSubtask*,int*,const void*,int,const void*,int);
struct SortSubtask {
SQLiteThread *pThread; /* Background thread, if any */
int bDone; /* Set if thread is finished but not joined */
VdbeSorter *pSorter; /* Sorter that owns this sub-task */
UnpackedRecord *pUnpacked; /* Space to unpack a record */
SorterList list; /* List for thread to write to a PMA */
int nPMA; /* Number of PMAs currently in file */
SorterCompare xCompare; /* Compare function to use */
SorterFile file; /* Temp file for level-0 PMAs */
SorterFile file2; /* Space for other PMAs */
};
/*
** Main sorter structure. A single instance of this is allocated for each
** sorter cursor created by the VDBE.
**
** mxKeysize:
** As records are added to the sorter by calls to sqlite3VdbeSorterWrite(),
** this variable is updated so as to be set to the size on disk of the
** largest record in the sorter.
*/
struct VdbeSorter {
int mnPmaSize; /* Minimum PMA size, in bytes */
int mxPmaSize; /* Maximum PMA size, in bytes. 0==no limit */
int mxKeysize; /* Largest serialized key seen so far */
int pgsz; /* Main database page size */
PmaReader *pReader; /* Readr data from here after Rewind() */
MergeEngine *pMerger; /* Or here, if bUseThreads==0 */
sqlite3 *db; /* Database connection */
KeyInfo *pKeyInfo; /* How to compare records */
UnpackedRecord *pUnpacked; /* Used by VdbeSorterCompare() */
SorterList list; /* List of in-memory records */
int iMemory; /* Offset of free space in list.aMemory */
int nMemory; /* Size of list.aMemory allocation in bytes */
u8 bUsePMA; /* True if one or more PMAs created */
u8 bUseThreads; /* True to use background threads */
u8 iPrev; /* Previous thread used to flush PMA */
u8 nTask; /* Size of aTask[] array */
u8 typeMask;
SortSubtask aTask[1]; /* One or more subtasks */
};
#define SORTER_TYPE_INTEGER 0x01
#define SORTER_TYPE_TEXT 0x02
/*
** An instance of the following object is used to read records out of a
** PMA, in sorted order. The next key to be read is cached in nKey/aKey.
** aKey might point into aMap or into aBuffer. If neither of those locations
** contain a contiguous representation of the key, then aAlloc is allocated
** and the key is copied into aAlloc and aKey is made to poitn to aAlloc.
**
** pFd==0 at EOF.
*/
struct PmaReader {
i64 iReadOff; /* Current read offset */
i64 iEof; /* 1 byte past EOF for this PmaReader */
int nAlloc; /* Bytes of space at aAlloc */
int nKey; /* Number of bytes in key */
sqlite3_file *pFd; /* File handle we are reading from */
u8 *aAlloc; /* Space for aKey if aBuffer and pMap wont work */
u8 *aKey; /* Pointer to current key */
u8 *aBuffer; /* Current read buffer */
int nBuffer; /* Size of read buffer in bytes */
u8 *aMap; /* Pointer to mapping of entire file */
IncrMerger *pIncr; /* Incremental merger */
};
/*
** Normally, a PmaReader object iterates through an existing PMA stored
** within a temp file. However, if the PmaReader.pIncr variable points to
** an object of the following type, it may be used to iterate/merge through
** multiple PMAs simultaneously.
**
** There are two types of IncrMerger object - single (bUseThread==0) and
** multi-threaded (bUseThread==1).
**
** A multi-threaded IncrMerger object uses two temporary files - aFile[0]
** and aFile[1]. Neither file is allowed to grow to more than mxSz bytes in
** size. When the IncrMerger is initialized, it reads enough data from
** pMerger to populate aFile[0]. It then sets variables within the
** corresponding PmaReader object to read from that file and kicks off
** a background thread to populate aFile[1] with the next mxSz bytes of
** sorted record data from pMerger.
**
** When the PmaReader reaches the end of aFile[0], it blocks until the
** background thread has finished populating aFile[1]. It then exchanges
** the contents of the aFile[0] and aFile[1] variables within this structure,
** sets the PmaReader fields to read from the new aFile[0] and kicks off
** another background thread to populate the new aFile[1]. And so on, until
** the contents of pMerger are exhausted.
**
** A single-threaded IncrMerger does not open any temporary files of its
** own. Instead, it has exclusive access to mxSz bytes of space beginning
** at offset iStartOff of file pTask->file2. And instead of using a
** background thread to prepare data for the PmaReader, with a single
** threaded IncrMerger the allocate part of pTask->file2 is "refilled" with
** keys from pMerger by the calling thread whenever the PmaReader runs out
** of data.
*/
struct IncrMerger {
SortSubtask *pTask; /* Task that owns this merger */
MergeEngine *pMerger; /* Merge engine thread reads data from */
i64 iStartOff; /* Offset to start writing file at */
int mxSz; /* Maximum bytes of data to store */
int bEof; /* Set to true when merge is finished */
int bUseThread; /* True to use a bg thread for this object */
SorterFile aFile[2]; /* aFile[0] for reading, [1] for writing */
};
/*
** An instance of this object is used for writing a PMA.
**
** The PMA is written one record at a time. Each record is of an arbitrary
** size. But I/O is more efficient if it occurs in page-sized blocks where
** each block is aligned on a page boundary. This object caches writes to
** the PMA so that aligned, page-size blocks are written.
*/
struct PmaWriter {
int eFWErr; /* Non-zero if in an error state */
u8 *aBuffer; /* Pointer to write buffer */
int nBuffer; /* Size of write buffer in bytes */
int iBufStart; /* First byte of buffer to write */
int iBufEnd; /* Last byte of buffer to write */
i64 iWriteOff; /* Offset of start of buffer in file */
sqlite3_file *pFd; /* File handle to write to */
};
/*
** This object is the header on a single record while that record is being
** held in memory and prior to being written out as part of a PMA.
**
** How the linked list is connected depends on how memory is being managed
** by this module. If using a separate allocation for each in-memory record
** (VdbeSorter.list.aMemory==0), then the list is always connected using the
** SorterRecord.u.pNext pointers.
**
** Or, if using the single large allocation method (VdbeSorter.list.aMemory!=0),
** then while records are being accumulated the list is linked using the
** SorterRecord.u.iNext offset. This is because the aMemory[] array may
** be sqlite3Realloc()ed while records are being accumulated. Once the VM
** has finished passing records to the sorter, or when the in-memory buffer
** is full, the list is sorted. As part of the sorting process, it is
** converted to use the SorterRecord.u.pNext pointers. See function
** vdbeSorterSort() for details.
*/
struct SorterRecord {
int nVal; /* Size of the record in bytes */
union {
SorterRecord *pNext; /* Pointer to next record in list */
int iNext; /* Offset within aMemory of next record */
} u;
/* The data for the record immediately follows this header */
};
/* Return a pointer to the buffer containing the record data for SorterRecord
** object p. Should be used as if:
**
** void *SRVAL(SorterRecord *p) { return (void*)&p[1]; }
*/
#define SRVAL(p) ((void*)((SorterRecord*)(p) + 1))
/* Maximum number of PMAs that a single MergeEngine can merge */
#define SORTER_MAX_MERGE_COUNT 16
static int vdbeIncrSwap(IncrMerger*);
static void vdbeIncrFree(IncrMerger *);
/*
** Free all memory belonging to the PmaReader object passed as the
** argument. All structure fields are set to zero before returning.
*/
static void vdbePmaReaderClear(PmaReader *pReadr){
sqlite3_free(pReadr->aAlloc);
sqlite3_free(pReadr->aBuffer);
if( pReadr->aMap ) sqlite3OsUnfetch(pReadr->pFd, 0, pReadr->aMap);
vdbeIncrFree(pReadr->pIncr);
memset(pReadr, 0, sizeof(PmaReader));
}
/*
** Read the next nByte bytes of data from the PMA p.
** If successful, set *ppOut to point to a buffer containing the data
** and return SQLITE_OK. Otherwise, if an error occurs, return an SQLite
** error code.
**
** The buffer returned in *ppOut is only valid until the
** next call to this function.
*/
static int vdbePmaReadBlob(
PmaReader *p, /* PmaReader from which to take the blob */
int nByte, /* Bytes of data to read */
u8 **ppOut /* OUT: Pointer to buffer containing data */
){
int iBuf; /* Offset within buffer to read from */
int nAvail; /* Bytes of data available in buffer */
if( p->aMap ){
*ppOut = &p->aMap[p->iReadOff];
p->iReadOff += nByte;
return SQLITE_OK;
}
assert( p->aBuffer );
/* If there is no more data to be read from the buffer, read the next
** p->nBuffer bytes of data from the file into it. Or, if there are less
** than p->nBuffer bytes remaining in the PMA, read all remaining data. */
iBuf = p->iReadOff % p->nBuffer;
if( iBuf==0 ){
int nRead; /* Bytes to read from disk */
int rc; /* sqlite3OsRead() return code */
/* Determine how many bytes of data to read. */
if( (p->iEof - p->iReadOff) > (i64)p->nBuffer ){
nRead = p->nBuffer;
}else{
nRead = (int)(p->iEof - p->iReadOff);
}
assert( nRead>0 );
/* Readr data from the file. Return early if an error occurs. */
rc = sqlite3OsRead(p->pFd, p->aBuffer, nRead, p->iReadOff);
assert( rc!=SQLITE_IOERR_SHORT_READ );
if( rc!=SQLITE_OK ) return rc;
}
nAvail = p->nBuffer - iBuf;
if( nByte<=nAvail ){
/* The requested data is available in the in-memory buffer. In this
** case there is no need to make a copy of the data, just return a
** pointer into the buffer to the caller. */
*ppOut = &p->aBuffer[iBuf];
p->iReadOff += nByte;
}else{
/* The requested data is not all available in the in-memory buffer.
** In this case, allocate space at p->aAlloc[] to copy the requested
** range into. Then return a copy of pointer p->aAlloc to the caller. */
int nRem; /* Bytes remaining to copy */
/* Extend the p->aAlloc[] allocation if required. */
if( p->nAlloc<nByte ){
u8 *aNew;
int nNew = MAX(128, p->nAlloc*2);
while( nByte>nNew ) nNew = nNew*2;
aNew = sqlite3Realloc(p->aAlloc, nNew);
if( !aNew ) return SQLITE_NOMEM;
p->nAlloc = nNew;
p->aAlloc = aNew;
}
/* Copy as much data as is available in the buffer into the start of
** p->aAlloc[]. */
memcpy(p->aAlloc, &p->aBuffer[iBuf], nAvail);
p->iReadOff += nAvail;
nRem = nByte - nAvail;
/* The following loop copies up to p->nBuffer bytes per iteration into
** the p->aAlloc[] buffer. */
while( nRem>0 ){
int rc; /* vdbePmaReadBlob() return code */
int nCopy; /* Number of bytes to copy */
u8 *aNext; /* Pointer to buffer to copy data from */
nCopy = nRem;
if( nRem>p->nBuffer ) nCopy = p->nBuffer;
rc = vdbePmaReadBlob(p, nCopy, &aNext);
if( rc!=SQLITE_OK ) return rc;
assert( aNext!=p->aAlloc );
memcpy(&p->aAlloc[nByte - nRem], aNext, nCopy);
nRem -= nCopy;
}
*ppOut = p->aAlloc;
}
return SQLITE_OK;
}
/*
** Read a varint from the stream of data accessed by p. Set *pnOut to
** the value read.
*/
static int vdbePmaReadVarint(PmaReader *p, u64 *pnOut){
int iBuf;
if( p->aMap ){
p->iReadOff += sqlite3GetVarint(&p->aMap[p->iReadOff], pnOut);
}else{
iBuf = p->iReadOff % p->nBuffer;
if( iBuf && (p->nBuffer-iBuf)>=9 ){
p->iReadOff += sqlite3GetVarint(&p->aBuffer[iBuf], pnOut);
}else{
u8 aVarint[16], *a;
int i = 0, rc;
do{
rc = vdbePmaReadBlob(p, 1, &a);
if( rc ) return rc;
aVarint[(i++)&0xf] = a[0];
}while( (a[0]&0x80)!=0 );
sqlite3GetVarint(aVarint, pnOut);
}
}
return SQLITE_OK;
}
/*
** Attempt to memory map file pFile. If successful, set *pp to point to the
** new mapping and return SQLITE_OK. If the mapping is not attempted
** (because the file is too large or the VFS layer is configured not to use
** mmap), return SQLITE_OK and set *pp to NULL.
**
** Or, if an error occurs, return an SQLite error code. The final value of
** *pp is undefined in this case.
*/
static int vdbeSorterMapFile(SortSubtask *pTask, SorterFile *pFile, u8 **pp){
int rc = SQLITE_OK;
if( pFile->iEof<=(i64)(pTask->pSorter->db->nMaxSorterMmap) ){
sqlite3_file *pFd = pFile->pFd;
if( pFd->pMethods->iVersion>=3 ){
rc = sqlite3OsFetch(pFd, 0, (int)pFile->iEof, (void**)pp);
testcase( rc!=SQLITE_OK );
}
}
return rc;
}
/*
** Attach PmaReader pReadr to file pFile (if it is not already attached to
** that file) and seek it to offset iOff within the file. Return SQLITE_OK
** if successful, or an SQLite error code if an error occurs.
*/
static int vdbePmaReaderSeek(
SortSubtask *pTask, /* Task context */
PmaReader *pReadr, /* Reader whose cursor is to be moved */
SorterFile *pFile, /* Sorter file to read from */
i64 iOff /* Offset in pFile */
){
int rc = SQLITE_OK;
assert( pReadr->pIncr==0 || pReadr->pIncr->bEof==0 );
if( sqlite3FaultSim(201) ) return SQLITE_IOERR_READ;
if( pReadr->aMap ){
sqlite3OsUnfetch(pReadr->pFd, 0, pReadr->aMap);
pReadr->aMap = 0;
}
pReadr->iReadOff = iOff;
pReadr->iEof = pFile->iEof;
pReadr->pFd = pFile->pFd;
rc = vdbeSorterMapFile(pTask, pFile, &pReadr->aMap);
if( rc==SQLITE_OK && pReadr->aMap==0 ){
int pgsz = pTask->pSorter->pgsz;
int iBuf = pReadr->iReadOff % pgsz;
if( pReadr->aBuffer==0 ){
pReadr->aBuffer = (u8*)sqlite3Malloc(pgsz);
if( pReadr->aBuffer==0 ) rc = SQLITE_NOMEM;
pReadr->nBuffer = pgsz;
}
if( rc==SQLITE_OK && iBuf ){
int nRead = pgsz - iBuf;
if( (pReadr->iReadOff + nRead) > pReadr->iEof ){
nRead = (int)(pReadr->iEof - pReadr->iReadOff);
}
rc = sqlite3OsRead(
pReadr->pFd, &pReadr->aBuffer[iBuf], nRead, pReadr->iReadOff
);
testcase( rc!=SQLITE_OK );
}
}
return rc;
}
/*
** Advance PmaReader pReadr to the next key in its PMA. Return SQLITE_OK if
** no error occurs, or an SQLite error code if one does.
*/
static int vdbePmaReaderNext(PmaReader *pReadr){
int rc = SQLITE_OK; /* Return Code */
u64 nRec = 0; /* Size of record in bytes */
if( pReadr->iReadOff>=pReadr->iEof ){
IncrMerger *pIncr = pReadr->pIncr;
int bEof = 1;
if( pIncr ){
rc = vdbeIncrSwap(pIncr);
if( rc==SQLITE_OK && pIncr->bEof==0 ){
rc = vdbePmaReaderSeek(
pIncr->pTask, pReadr, &pIncr->aFile[0], pIncr->iStartOff
);
bEof = 0;
}
}
if( bEof ){
/* This is an EOF condition */
vdbePmaReaderClear(pReadr);
testcase( rc!=SQLITE_OK );
return rc;
}
}
if( rc==SQLITE_OK ){
rc = vdbePmaReadVarint(pReadr, &nRec);
}
if( rc==SQLITE_OK ){
pReadr->nKey = (int)nRec;
rc = vdbePmaReadBlob(pReadr, (int)nRec, &pReadr->aKey);
testcase( rc!=SQLITE_OK );
}
return rc;
}
/*
** Initialize PmaReader pReadr to scan through the PMA stored in file pFile
** starting at offset iStart and ending at offset iEof-1. This function
** leaves the PmaReader pointing to the first key in the PMA (or EOF if the
** PMA is empty).
**
** If the pnByte parameter is NULL, then it is assumed that the file
** contains a single PMA, and that that PMA omits the initial length varint.
*/
static int vdbePmaReaderInit(
SortSubtask *pTask, /* Task context */
SorterFile *pFile, /* Sorter file to read from */
i64 iStart, /* Start offset in pFile */
PmaReader *pReadr, /* PmaReader to populate */
i64 *pnByte /* IN/OUT: Increment this value by PMA size */
){
int rc;
assert( pFile->iEof>iStart );
assert( pReadr->aAlloc==0 && pReadr->nAlloc==0 );
assert( pReadr->aBuffer==0 );
assert( pReadr->aMap==0 );
rc = vdbePmaReaderSeek(pTask, pReadr, pFile, iStart);
if( rc==SQLITE_OK ){
u64 nByte; /* Size of PMA in bytes */
rc = vdbePmaReadVarint(pReadr, &nByte);
pReadr->iEof = pReadr->iReadOff + nByte;
*pnByte += nByte;
}
if( rc==SQLITE_OK ){
rc = vdbePmaReaderNext(pReadr);
}
return rc;
}
/*
** A version of vdbeSorterCompare() that assumes that it has already been
** determined that the first field of key1 is equal to the first field of
** key2.
*/
static int vdbeSorterCompareTail(
SortSubtask *pTask, /* Subtask context (for pKeyInfo) */
int *pbKey2Cached, /* True if pTask->pUnpacked is pKey2 */
const void *pKey1, int nKey1, /* Left side of comparison */
const void *pKey2, int nKey2 /* Right side of comparison */
){
UnpackedRecord *r2 = pTask->pUnpacked;
if( *pbKey2Cached==0 ){
sqlite3VdbeRecordUnpack(pTask->pSorter->pKeyInfo, nKey2, pKey2, r2);
*pbKey2Cached = 1;
}
return sqlite3VdbeRecordCompareWithSkip(nKey1, pKey1, r2, 1);
}
/*
** Compare key1 (buffer pKey1, size nKey1 bytes) with key2 (buffer pKey2,
** size nKey2 bytes). Use (pTask->pKeyInfo) for the collation sequences
** used by the comparison. Return the result of the comparison.
**
** If IN/OUT parameter *pbKey2Cached is true when this function is called,
** it is assumed that (pTask->pUnpacked) contains the unpacked version
** of key2. If it is false, (pTask->pUnpacked) is populated with the unpacked
** version of key2 and *pbKey2Cached set to true before returning.
**
** If an OOM error is encountered, (pTask->pUnpacked->error_rc) is set
** to SQLITE_NOMEM.
*/
static int vdbeSorterCompare(
SortSubtask *pTask, /* Subtask context (for pKeyInfo) */
int *pbKey2Cached, /* True if pTask->pUnpacked is pKey2 */
const void *pKey1, int nKey1, /* Left side of comparison */
const void *pKey2, int nKey2 /* Right side of comparison */
){
UnpackedRecord *r2 = pTask->pUnpacked;
if( !*pbKey2Cached ){
sqlite3VdbeRecordUnpack(pTask->pSorter->pKeyInfo, nKey2, pKey2, r2);
*pbKey2Cached = 1;
}
return sqlite3VdbeRecordCompare(nKey1, pKey1, r2);
}
/*
** A specially optimized version of vdbeSorterCompare() that assumes that
** the first field of each key is a TEXT value and that the collation
** sequence to compare them with is BINARY.
*/
static int vdbeSorterCompareText(
SortSubtask *pTask, /* Subtask context (for pKeyInfo) */
int *pbKey2Cached, /* True if pTask->pUnpacked is pKey2 */
const void *pKey1, int nKey1, /* Left side of comparison */
const void *pKey2, int nKey2 /* Right side of comparison */
){
const u8 * const p1 = (const u8 * const)pKey1;
const u8 * const p2 = (const u8 * const)pKey2;
const u8 * const v1 = &p1[ p1[0] ]; /* Pointer to value 1 */
const u8 * const v2 = &p2[ p2[0] ]; /* Pointer to value 2 */
int n1;
int n2;
int res;
getVarint32(&p1[1], n1); n1 = (n1 - 13) / 2;
getVarint32(&p2[1], n2); n2 = (n2 - 13) / 2;
res = memcmp(v1, v2, MIN(n1, n2));
if( res==0 ){
res = n1 - n2;
}
if( res==0 ){
if( pTask->pSorter->pKeyInfo->nField>1 ){
res = vdbeSorterCompareTail(
pTask, pbKey2Cached, pKey1, nKey1, pKey2, nKey2
);
}
}else{
if( pTask->pSorter->pKeyInfo->aSortOrder[0] ){
res = res * -1;
}
}
return res;
}
/*
** A specially optimized version of vdbeSorterCompare() that assumes that
** the first field of each key is an INTEGER value.
*/
static int vdbeSorterCompareInt(
SortSubtask *pTask, /* Subtask context (for pKeyInfo) */
int *pbKey2Cached, /* True if pTask->pUnpacked is pKey2 */
const void *pKey1, int nKey1, /* Left side of comparison */
const void *pKey2, int nKey2 /* Right side of comparison */
){
const u8 * const p1 = (const u8 * const)pKey1;
const u8 * const p2 = (const u8 * const)pKey2;
const int s1 = p1[1]; /* Left hand serial type */
const int s2 = p2[1]; /* Right hand serial type */
const u8 * const v1 = &p1[ p1[0] ]; /* Pointer to value 1 */
const u8 * const v2 = &p2[ p2[0] ]; /* Pointer to value 2 */
int res; /* Return value */
assert( (s1>0 && s1<7) || s1==8 || s1==9 );
assert( (s2>0 && s2<7) || s2==8 || s2==9 );
if( s1>7 && s2>7 ){
res = s1 - s2;
}else{
if( s1==s2 ){
if( (*v1 ^ *v2) & 0x80 ){
/* The two values have different signs */
res = (*v1 & 0x80) ? -1 : +1;
}else{
/* The two values have the same sign. Compare using memcmp(). */
static const u8 aLen[] = {0, 1, 2, 3, 4, 6, 8 };
int i;
res = 0;
for(i=0; i<aLen[s1]; i++){
if( (res = v1[i] - v2[i]) ) break;
}
}
}else{
if( s2>7 ){
res = +1;
}else if( s1>7 ){
res = -1;
}else{
res = s1 - s2;
}
assert( res!=0 );
if( res>0 ){
if( *v1 & 0x80 ) res = -1;
}else{
if( *v2 & 0x80 ) res = +1;
}
}
}
if( res==0 ){
if( pTask->pSorter->pKeyInfo->nField>1 ){
res = vdbeSorterCompareTail(
pTask, pbKey2Cached, pKey1, nKey1, pKey2, nKey2
);
}
}else if( pTask->pSorter->pKeyInfo->aSortOrder[0] ){
res = res * -1;
}
return res;
}
/*
** Initialize the temporary index cursor just opened as a sorter cursor.
**
** Usually, the sorter module uses the value of (pCsr->pKeyInfo->nField)
** to determine the number of fields that should be compared from the
** records being sorted. However, if the value passed as argument nField
** is non-zero and the sorter is able to guarantee a stable sort, nField
** is used instead. This is used when sorting records for a CREATE INDEX
** statement. In this case, keys are always delivered to the sorter in
** order of the primary key, which happens to be make up the final part
** of the records being sorted. So if the sort is stable, there is never
** any reason to compare PK fields and they can be ignored for a small
** performance boost.
**
** The sorter can guarantee a stable sort when running in single-threaded
** mode, but not in multi-threaded mode.
**
** SQLITE_OK is returned if successful, or an SQLite error code otherwise.
*/
int sqlite3VdbeSorterInit(
sqlite3 *db, /* Database connection (for malloc()) */
int nField, /* Number of key fields in each record */
VdbeCursor *pCsr /* Cursor that holds the new sorter */
){
int pgsz; /* Page size of main database */
int i; /* Used to iterate through aTask[] */
int mxCache; /* Cache size */
VdbeSorter *pSorter; /* The new sorter */
KeyInfo *pKeyInfo; /* Copy of pCsr->pKeyInfo with db==0 */
int szKeyInfo; /* Size of pCsr->pKeyInfo in bytes */
int sz; /* Size of pSorter in bytes */
int rc = SQLITE_OK;
#if SQLITE_MAX_WORKER_THREADS==0
# define nWorker 0
#else
int nWorker;
#endif
/* Initialize the upper limit on the number of worker threads */
#if SQLITE_MAX_WORKER_THREADS>0
if( sqlite3TempInMemory(db) || sqlite3GlobalConfig.bCoreMutex==0 ){
nWorker = 0;
}else{
nWorker = db->aLimit[SQLITE_LIMIT_WORKER_THREADS];
}
#endif
/* Do not allow the total number of threads (main thread + all workers)
** to exceed the maximum merge count */
#if SQLITE_MAX_WORKER_THREADS>=SORTER_MAX_MERGE_COUNT
if( nWorker>=SORTER_MAX_MERGE_COUNT ){
nWorker = SORTER_MAX_MERGE_COUNT-1;
}
#endif
assert( pCsr->pKeyInfo && pCsr->pBt==0 );
szKeyInfo = sizeof(KeyInfo) + (pCsr->pKeyInfo->nField-1)*sizeof(CollSeq*);
sz = sizeof(VdbeSorter) + nWorker * sizeof(SortSubtask);
pSorter = (VdbeSorter*)sqlite3DbMallocZero(db, sz + szKeyInfo);
pCsr->pSorter = pSorter;
if( pSorter==0 ){
rc = SQLITE_NOMEM;
}else{
pSorter->pKeyInfo = pKeyInfo = (KeyInfo*)((u8*)pSorter + sz);
memcpy(pKeyInfo, pCsr->pKeyInfo, szKeyInfo);
pKeyInfo->db = 0;
if( nField && nWorker==0 ){
pKeyInfo->nXField += (pKeyInfo->nField - nField);
pKeyInfo->nField = nField;
}
pSorter->pgsz = pgsz = sqlite3BtreeGetPageSize(db->aDb[0].pBt);
pSorter->nTask = nWorker + 1;
pSorter->iPrev = nWorker-1;
pSorter->bUseThreads = (pSorter->nTask>1);
pSorter->db = db;
for(i=0; i<pSorter->nTask; i++){
SortSubtask *pTask = &pSorter->aTask[i];
pTask->pSorter = pSorter;
}
if( !sqlite3TempInMemory(db) ){
u32 szPma = sqlite3GlobalConfig.szPma;
pSorter->mnPmaSize = szPma * pgsz;
mxCache = db->aDb[0].pSchema->cache_size;
if( mxCache<(int)szPma ) mxCache = (int)szPma;
pSorter->mxPmaSize = MIN((i64)mxCache*pgsz, SQLITE_MAX_PMASZ);
/* EVIDENCE-OF: R-26747-61719 When the application provides any amount of
** scratch memory using SQLITE_CONFIG_SCRATCH, SQLite avoids unnecessary
** large heap allocations.
*/
if( sqlite3GlobalConfig.pScratch==0 ){
assert( pSorter->iMemory==0 );
pSorter->nMemory = pgsz;
pSorter->list.aMemory = (u8*)sqlite3Malloc(pgsz);
if( !pSorter->list.aMemory ) rc = SQLITE_NOMEM;
}
}
if( (pKeyInfo->nField+pKeyInfo->nXField)<13
&& (pKeyInfo->aColl[0]==0 || pKeyInfo->aColl[0]==db->pDfltColl)
){
pSorter->typeMask = SORTER_TYPE_INTEGER | SORTER_TYPE_TEXT;
}
}
return rc;
}
#undef nWorker /* Defined at the top of this function */
/*
** Free the list of sorted records starting at pRecord.
*/
static void vdbeSorterRecordFree(sqlite3 *db, SorterRecord *pRecord){
SorterRecord *p;
SorterRecord *pNext;
for(p=pRecord; p; p=pNext){
pNext = p->u.pNext;
sqlite3DbFree(db, p);
}
}
/*
** Free all resources owned by the object indicated by argument pTask. All
** fields of *pTask are zeroed before returning.
*/
static void vdbeSortSubtaskCleanup(sqlite3 *db, SortSubtask *pTask){
sqlite3DbFree(db, pTask->pUnpacked);
#if SQLITE_MAX_WORKER_THREADS>0
/* pTask->list.aMemory can only be non-zero if it was handed memory
** from the main thread. That only occurs SQLITE_MAX_WORKER_THREADS>0 */
if( pTask->list.aMemory ){
sqlite3_free(pTask->list.aMemory);
}else
#endif
{
assert( pTask->list.aMemory==0 );
vdbeSorterRecordFree(0, pTask->list.pList);
}
if( pTask->file.pFd ){
sqlite3OsCloseFree(pTask->file.pFd);
}
if( pTask->file2.pFd ){
sqlite3OsCloseFree(pTask->file2.pFd);
}
memset(pTask, 0, sizeof(SortSubtask));
}
#ifdef SQLITE_DEBUG_SORTER_THREADS
static void vdbeSorterWorkDebug(SortSubtask *pTask, const char *zEvent){
i64 t;
int iTask = (pTask - pTask->pSorter->aTask);
sqlite3OsCurrentTimeInt64(pTask->pSorter->db->pVfs, &t);
fprintf(stderr, "%lld:%d %s\n", t, iTask, zEvent);
}
static void vdbeSorterRewindDebug(const char *zEvent){
i64 t;
sqlite3OsCurrentTimeInt64(sqlite3_vfs_find(0), &t);
fprintf(stderr, "%lld:X %s\n", t, zEvent);
}
static void vdbeSorterPopulateDebug(
SortSubtask *pTask,
const char *zEvent
){
i64 t;
int iTask = (pTask - pTask->pSorter->aTask);
sqlite3OsCurrentTimeInt64(pTask->pSorter->db->pVfs, &t);
fprintf(stderr, "%lld:bg%d %s\n", t, iTask, zEvent);
}
static void vdbeSorterBlockDebug(
SortSubtask *pTask,
int bBlocked,
const char *zEvent
){
if( bBlocked ){
i64 t;
sqlite3OsCurrentTimeInt64(pTask->pSorter->db->pVfs, &t);
fprintf(stderr, "%lld:main %s\n", t, zEvent);
}
}
#else
# define vdbeSorterWorkDebug(x,y)
# define vdbeSorterRewindDebug(y)
# define vdbeSorterPopulateDebug(x,y)
# define vdbeSorterBlockDebug(x,y,z)
#endif
#if SQLITE_MAX_WORKER_THREADS>0
/*
** Join thread pTask->thread.
*/
static int vdbeSorterJoinThread(SortSubtask *pTask){
int rc = SQLITE_OK;
if( pTask->pThread ){
#ifdef SQLITE_DEBUG_SORTER_THREADS
int bDone = pTask->bDone;
#endif
void *pRet = SQLITE_INT_TO_PTR(SQLITE_ERROR);
vdbeSorterBlockDebug(pTask, !bDone, "enter");
(void)sqlite3ThreadJoin(pTask->pThread, &pRet);
vdbeSorterBlockDebug(pTask, !bDone, "exit");
rc = SQLITE_PTR_TO_INT(pRet);
assert( pTask->bDone==1 );
pTask->bDone = 0;
pTask->pThread = 0;
}
return rc;
}
/*
** Launch a background thread to run xTask(pIn).
*/
static int vdbeSorterCreateThread(
SortSubtask *pTask, /* Thread will use this task object */
void *(*xTask)(void*), /* Routine to run in a separate thread */
void *pIn /* Argument passed into xTask() */
){
assert( pTask->pThread==0 && pTask->bDone==0 );
return sqlite3ThreadCreate(&pTask->pThread, xTask, pIn);
}
/*
** Join all outstanding threads launched by SorterWrite() to create
** level-0 PMAs.
*/
static int vdbeSorterJoinAll(VdbeSorter *pSorter, int rcin){
int rc = rcin;
int i;
/* This function is always called by the main user thread.
**
** If this function is being called after SorterRewind() has been called,
** it is possible that thread pSorter->aTask[pSorter->nTask-1].pThread
** is currently attempt to join one of the other threads. To avoid a race
** condition where this thread also attempts to join the same object, join
** thread pSorter->aTask[pSorter->nTask-1].pThread first. */
for(i=pSorter->nTask-1; i>=0; i--){
SortSubtask *pTask = &pSorter->aTask[i];
int rc2 = vdbeSorterJoinThread(pTask);
if( rc==SQLITE_OK ) rc = rc2;
}
return rc;
}
#else
# define vdbeSorterJoinAll(x,rcin) (rcin)
# define vdbeSorterJoinThread(pTask) SQLITE_OK
#endif
/*
** Allocate a new MergeEngine object capable of handling up to
** nReader PmaReader inputs.
**
** nReader is automatically rounded up to the next power of two.
** nReader may not exceed SORTER_MAX_MERGE_COUNT even after rounding up.
*/
static MergeEngine *vdbeMergeEngineNew(int nReader){
int N = 2; /* Smallest power of two >= nReader */
int nByte; /* Total bytes of space to allocate */
MergeEngine *pNew; /* Pointer to allocated object to return */
assert( nReader<=SORTER_MAX_MERGE_COUNT );
while( N<nReader ) N += N;
nByte = sizeof(MergeEngine) + N * (sizeof(int) + sizeof(PmaReader));
pNew = sqlite3FaultSim(100) ? 0 : (MergeEngine*)sqlite3MallocZero(nByte);
if( pNew ){
pNew->nTree = N;
pNew->pTask = 0;
pNew->aReadr = (PmaReader*)&pNew[1];
pNew->aTree = (int*)&pNew->aReadr[N];
}
return pNew;
}
/*
** Free the MergeEngine object passed as the only argument.
*/
static void vdbeMergeEngineFree(MergeEngine *pMerger){
int i;
if( pMerger ){
for(i=0; i<pMerger->nTree; i++){
vdbePmaReaderClear(&pMerger->aReadr[i]);
}
}
sqlite3_free(pMerger);
}
/*
** Free all resources associated with the IncrMerger object indicated by
** the first argument.
*/
static void vdbeIncrFree(IncrMerger *pIncr){
if( pIncr ){
#if SQLITE_MAX_WORKER_THREADS>0
if( pIncr->bUseThread ){
vdbeSorterJoinThread(pIncr->pTask);
if( pIncr->aFile[0].pFd ) sqlite3OsCloseFree(pIncr->aFile[0].pFd);
if( pIncr->aFile[1].pFd ) sqlite3OsCloseFree(pIncr->aFile[1].pFd);
}
#endif
vdbeMergeEngineFree(pIncr->pMerger);
sqlite3_free(pIncr);
}
}
/*
** Reset a sorting cursor back to its original empty state.
*/
void sqlite3VdbeSorterReset(sqlite3 *db, VdbeSorter *pSorter){
int i;
(void)vdbeSorterJoinAll(pSorter, SQLITE_OK);
assert( pSorter->bUseThreads || pSorter->pReader==0 );
#if SQLITE_MAX_WORKER_THREADS>0
if( pSorter->pReader ){
vdbePmaReaderClear(pSorter->pReader);
sqlite3DbFree(db, pSorter->pReader);
pSorter->pReader = 0;
}
#endif
vdbeMergeEngineFree(pSorter->pMerger);
pSorter->pMerger = 0;
for(i=0; i<pSorter->nTask; i++){
SortSubtask *pTask = &pSorter->aTask[i];
vdbeSortSubtaskCleanup(db, pTask);
pTask->pSorter = pSorter;
}
if( pSorter->list.aMemory==0 ){
vdbeSorterRecordFree(0, pSorter->list.pList);
}
pSorter->list.pList = 0;
pSorter->list.szPMA = 0;
pSorter->bUsePMA = 0;
pSorter->iMemory = 0;
pSorter->mxKeysize = 0;
sqlite3DbFree(db, pSorter->pUnpacked);
pSorter->pUnpacked = 0;
}
/*
** Free any cursor components allocated by sqlite3VdbeSorterXXX routines.
*/
void sqlite3VdbeSorterClose(sqlite3 *db, VdbeCursor *pCsr){
VdbeSorter *pSorter = pCsr->pSorter;
if( pSorter ){
sqlite3VdbeSorterReset(db, pSorter);
sqlite3_free(pSorter->list.aMemory);
sqlite3DbFree(db, pSorter);
pCsr->pSorter = 0;
}
}
#if SQLITE_MAX_MMAP_SIZE>0
/*
** The first argument is a file-handle open on a temporary file. The file
** is guaranteed to be nByte bytes or smaller in size. This function
** attempts to extend the file to nByte bytes in size and to ensure that
** the VFS has memory mapped it.
**
** Whether or not the file does end up memory mapped of course depends on
** the specific VFS implementation.
*/
static void vdbeSorterExtendFile(sqlite3 *db, sqlite3_file *pFd, i64 nByte){
if( nByte<=(i64)(db->nMaxSorterMmap) && pFd->pMethods->iVersion>=3 ){
void *p = 0;
int chunksize = 4*1024;
sqlite3OsFileControlHint(pFd, SQLITE_FCNTL_CHUNK_SIZE, &chunksize);
sqlite3OsFileControlHint(pFd, SQLITE_FCNTL_SIZE_HINT, &nByte);
sqlite3OsFetch(pFd, 0, (int)nByte, &p);
sqlite3OsUnfetch(pFd, 0, p);
}
}
#else
# define vdbeSorterExtendFile(x,y,z)
#endif
/*
** Allocate space for a file-handle and open a temporary file. If successful,
** set *ppFd to point to the malloc'd file-handle and return SQLITE_OK.
** Otherwise, set *ppFd to 0 and return an SQLite error code.
*/
static int vdbeSorterOpenTempFile(
sqlite3 *db, /* Database handle doing sort */
i64 nExtend, /* Attempt to extend file to this size */
sqlite3_file **ppFd
){
int rc;
if( sqlite3FaultSim(202) ) return SQLITE_IOERR_ACCESS;
rc = sqlite3OsOpenMalloc(db->pVfs, 0, ppFd,
SQLITE_OPEN_TEMP_JOURNAL |
SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE |
SQLITE_OPEN_EXCLUSIVE | SQLITE_OPEN_DELETEONCLOSE, &rc
);
if( rc==SQLITE_OK ){
i64 max = SQLITE_MAX_MMAP_SIZE;
sqlite3OsFileControlHint(*ppFd, SQLITE_FCNTL_MMAP_SIZE, (void*)&max);
if( nExtend>0 ){
vdbeSorterExtendFile(db, *ppFd, nExtend);
}
}
return rc;
}
/*
** If it has not already been allocated, allocate the UnpackedRecord
** structure at pTask->pUnpacked. Return SQLITE_OK if successful (or
** if no allocation was required), or SQLITE_NOMEM otherwise.
*/
static int vdbeSortAllocUnpacked(SortSubtask *pTask){
if( pTask->pUnpacked==0 ){
char *pFree;
pTask->pUnpacked = sqlite3VdbeAllocUnpackedRecord(
pTask->pSorter->pKeyInfo, 0, 0, &pFree
);
assert( pTask->pUnpacked==(UnpackedRecord*)pFree );
if( pFree==0 ) return SQLITE_NOMEM;
pTask->pUnpacked->nField = pTask->pSorter->pKeyInfo->nField;
pTask->pUnpacked->errCode = 0;
}
return SQLITE_OK;
}
/*
** Merge the two sorted lists p1 and p2 into a single list.
** Set *ppOut to the head of the new list.
*/
static void vdbeSorterMerge(
SortSubtask *pTask, /* Calling thread context */
SorterRecord *p1, /* First list to merge */
SorterRecord *p2, /* Second list to merge */
SorterRecord **ppOut /* OUT: Head of merged list */
){
SorterRecord *pFinal = 0;
SorterRecord **pp = &pFinal;
int bCached = 0;
while( p1 && p2 ){
int res;
res = pTask->xCompare(
pTask, &bCached, SRVAL(p1), p1->nVal, SRVAL(p2), p2->nVal
);
if( res<=0 ){
*pp = p1;
pp = &p1->u.pNext;
p1 = p1->u.pNext;
}else{
*pp = p2;
pp = &p2->u.pNext;
p2 = p2->u.pNext;
bCached = 0;
}
}
*pp = p1 ? p1 : p2;
*ppOut = pFinal;
}
/*
** Return the SorterCompare function to compare values collected by the
** sorter object passed as the only argument.
*/
static SorterCompare vdbeSorterGetCompare(VdbeSorter *p){
if( p->typeMask==SORTER_TYPE_INTEGER ){
return vdbeSorterCompareInt;
}else if( p->typeMask==SORTER_TYPE_TEXT ){
return vdbeSorterCompareText;
}
return vdbeSorterCompare;
}
/*
** Sort the linked list of records headed at pTask->pList. Return
** SQLITE_OK if successful, or an SQLite error code (i.e. SQLITE_NOMEM) if
** an error occurs.
*/
static int vdbeSorterSort(SortSubtask *pTask, SorterList *pList){
int i;
SorterRecord **aSlot;
SorterRecord *p;
int rc;
rc = vdbeSortAllocUnpacked(pTask);
if( rc!=SQLITE_OK ) return rc;
p = pList->pList;
pTask->xCompare = vdbeSorterGetCompare(pTask->pSorter);
aSlot = (SorterRecord **)sqlite3MallocZero(64 * sizeof(SorterRecord *));
if( !aSlot ){
return SQLITE_NOMEM;
}
while( p ){
SorterRecord *pNext;
if( pList->aMemory ){
if( (u8*)p==pList->aMemory ){
pNext = 0;
}else{
assert( p->u.iNext<sqlite3MallocSize(pList->aMemory) );
pNext = (SorterRecord*)&pList->aMemory[p->u.iNext];
}
}else{
pNext = p->u.pNext;
}
p->u.pNext = 0;
for(i=0; aSlot[i]; i++){
vdbeSorterMerge(pTask, p, aSlot[i], &p);
aSlot[i] = 0;
}
aSlot[i] = p;
p = pNext;
}
p = 0;
for(i=0; i<64; i++){
vdbeSorterMerge(pTask, p, aSlot[i], &p);
}
pList->pList = p;
sqlite3_free(aSlot);
assert( pTask->pUnpacked->errCode==SQLITE_OK
|| pTask->pUnpacked->errCode==SQLITE_NOMEM
);
return pTask->pUnpacked->errCode;
}
/*
** Initialize a PMA-writer object.
*/
static void vdbePmaWriterInit(
sqlite3_file *pFd, /* File handle to write to */
PmaWriter *p, /* Object to populate */
int nBuf, /* Buffer size */
i64 iStart /* Offset of pFd to begin writing at */
){
memset(p, 0, sizeof(PmaWriter));
p->aBuffer = (u8*)sqlite3Malloc(nBuf);
if( !p->aBuffer ){
p->eFWErr = SQLITE_NOMEM;
}else{
p->iBufEnd = p->iBufStart = (iStart % nBuf);
p->iWriteOff = iStart - p->iBufStart;
p->nBuffer = nBuf;
p->pFd = pFd;
}
}
/*
** Write nData bytes of data to the PMA. Return SQLITE_OK
** if successful, or an SQLite error code if an error occurs.
*/
static void vdbePmaWriteBlob(PmaWriter *p, u8 *pData, int nData){
int nRem = nData;
while( nRem>0 && p->eFWErr==0 ){
int nCopy = nRem;
if( nCopy>(p->nBuffer - p->iBufEnd) ){
nCopy = p->nBuffer - p->iBufEnd;
}
memcpy(&p->aBuffer[p->iBufEnd], &pData[nData-nRem], nCopy);
p->iBufEnd += nCopy;
if( p->iBufEnd==p->nBuffer ){
p->eFWErr = sqlite3OsWrite(p->pFd,
&p->aBuffer[p->iBufStart], p->iBufEnd - p->iBufStart,
p->iWriteOff + p->iBufStart
);
p->iBufStart = p->iBufEnd = 0;
p->iWriteOff += p->nBuffer;
}
assert( p->iBufEnd<p->nBuffer );
nRem -= nCopy;
}
}
/*
** Flush any buffered data to disk and clean up the PMA-writer object.
** The results of using the PMA-writer after this call are undefined.
** Return SQLITE_OK if flushing the buffered data succeeds or is not
** required. Otherwise, return an SQLite error code.
**
** Before returning, set *piEof to the offset immediately following the
** last byte written to the file.
*/
static int vdbePmaWriterFinish(PmaWriter *p, i64 *piEof){
int rc;
if( p->eFWErr==0 && ALWAYS(p->aBuffer) && p->iBufEnd>p->iBufStart ){
p->eFWErr = sqlite3OsWrite(p->pFd,
&p->aBuffer[p->iBufStart], p->iBufEnd - p->iBufStart,
p->iWriteOff + p->iBufStart
);
}
*piEof = (p->iWriteOff + p->iBufEnd);
sqlite3_free(p->aBuffer);
rc = p->eFWErr;
memset(p, 0, sizeof(PmaWriter));
return rc;
}
/*
** Write value iVal encoded as a varint to the PMA. Return
** SQLITE_OK if successful, or an SQLite error code if an error occurs.
*/
static void vdbePmaWriteVarint(PmaWriter *p, u64 iVal){
int nByte;
u8 aByte[10];
nByte = sqlite3PutVarint(aByte, iVal);
vdbePmaWriteBlob(p, aByte, nByte);
}
/*
** Write the current contents of in-memory linked-list pList to a level-0
** PMA in the temp file belonging to sub-task pTask. Return SQLITE_OK if
** successful, or an SQLite error code otherwise.
**
** The format of a PMA is:
**
** * A varint. This varint contains the total number of bytes of content
** in the PMA (not including the varint itself).
**
** * One or more records packed end-to-end in order of ascending keys.
** Each record consists of a varint followed by a blob of data (the
** key). The varint is the number of bytes in the blob of data.
*/
static int vdbeSorterListToPMA(SortSubtask *pTask, SorterList *pList){
sqlite3 *db = pTask->pSorter->db;
int rc = SQLITE_OK; /* Return code */
PmaWriter writer; /* Object used to write to the file */
#ifdef SQLITE_DEBUG
/* Set iSz to the expected size of file pTask->file after writing the PMA.
** This is used by an assert() statement at the end of this function. */
i64 iSz = pList->szPMA + sqlite3VarintLen(pList->szPMA) + pTask->file.iEof;
#endif
vdbeSorterWorkDebug(pTask, "enter");
memset(&writer, 0, sizeof(PmaWriter));
assert( pList->szPMA>0 );
/* If the first temporary PMA file has not been opened, open it now. */
if( pTask->file.pFd==0 ){
rc = vdbeSorterOpenTempFile(db, 0, &pTask->file.pFd);
assert( rc!=SQLITE_OK || pTask->file.pFd );
assert( pTask->file.iEof==0 );
assert( pTask->nPMA==0 );
}
/* Try to get the file to memory map */
if( rc==SQLITE_OK ){
vdbeSorterExtendFile(db, pTask->file.pFd, pTask->file.iEof+pList->szPMA+9);
}
/* Sort the list */
if( rc==SQLITE_OK ){
rc = vdbeSorterSort(pTask, pList);
}
if( rc==SQLITE_OK ){
SorterRecord *p;
SorterRecord *pNext = 0;
vdbePmaWriterInit(pTask->file.pFd, &writer, pTask->pSorter->pgsz,
pTask->file.iEof);
pTask->nPMA++;
vdbePmaWriteVarint(&writer, pList->szPMA);
for(p=pList->pList; p; p=pNext){
pNext = p->u.pNext;
vdbePmaWriteVarint(&writer, p->nVal);
vdbePmaWriteBlob(&writer, SRVAL(p), p->nVal);
if( pList->aMemory==0 ) sqlite3_free(p);
}
pList->pList = p;
rc = vdbePmaWriterFinish(&writer, &pTask->file.iEof);
}
vdbeSorterWorkDebug(pTask, "exit");
assert( rc!=SQLITE_OK || pList->pList==0 );
assert( rc!=SQLITE_OK || pTask->file.iEof==iSz );
return rc;
}
/*
** Advance the MergeEngine to its next entry.
** Set *pbEof to true there is no next entry because
** the MergeEngine has reached the end of all its inputs.
**
** Return SQLITE_OK if successful or an error code if an error occurs.
*/
static int vdbeMergeEngineStep(
MergeEngine *pMerger, /* The merge engine to advance to the next row */
int *pbEof /* Set TRUE at EOF. Set false for more content */
){
int rc;
int iPrev = pMerger->aTree[1];/* Index of PmaReader to advance */
SortSubtask *pTask = pMerger->pTask;
/* Advance the current PmaReader */
rc = vdbePmaReaderNext(&pMerger->aReadr[iPrev]);
/* Update contents of aTree[] */
if( rc==SQLITE_OK ){
int i; /* Index of aTree[] to recalculate */
PmaReader *pReadr1; /* First PmaReader to compare */
PmaReader *pReadr2; /* Second PmaReader to compare */
int bCached = 0;
/* Find the first two PmaReaders to compare. The one that was just
** advanced (iPrev) and the one next to it in the array. */
pReadr1 = &pMerger->aReadr[(iPrev & 0xFFFE)];
pReadr2 = &pMerger->aReadr[(iPrev | 0x0001)];
for(i=(pMerger->nTree+iPrev)/2; i>0; i=i/2){
/* Compare pReadr1 and pReadr2. Store the result in variable iRes. */
int iRes;
if( pReadr1->pFd==0 ){
iRes = +1;
}else if( pReadr2->pFd==0 ){
iRes = -1;
}else{
iRes = pTask->xCompare(pTask, &bCached,
pReadr1->aKey, pReadr1->nKey, pReadr2->aKey, pReadr2->nKey
);
}
/* If pReadr1 contained the smaller value, set aTree[i] to its index.
** Then set pReadr2 to the next PmaReader to compare to pReadr1. In this
** case there is no cache of pReadr2 in pTask->pUnpacked, so set
** pKey2 to point to the record belonging to pReadr2.
**
** Alternatively, if pReadr2 contains the smaller of the two values,
** set aTree[i] to its index and update pReadr1. If vdbeSorterCompare()
** was actually called above, then pTask->pUnpacked now contains
** a value equivalent to pReadr2. So set pKey2 to NULL to prevent
** vdbeSorterCompare() from decoding pReadr2 again.
**
** If the two values were equal, then the value from the oldest
** PMA should be considered smaller. The VdbeSorter.aReadr[] array
** is sorted from oldest to newest, so pReadr1 contains older values
** than pReadr2 iff (pReadr1<pReadr2). */
if( iRes<0 || (iRes==0 && pReadr1<pReadr2) ){
pMerger->aTree[i] = (int)(pReadr1 - pMerger->aReadr);
pReadr2 = &pMerger->aReadr[ pMerger->aTree[i ^ 0x0001] ];
bCached = 0;
}else{
if( pReadr1->pFd ) bCached = 0;
pMerger->aTree[i] = (int)(pReadr2 - pMerger->aReadr);
pReadr1 = &pMerger->aReadr[ pMerger->aTree[i ^ 0x0001] ];
}
}
*pbEof = (pMerger->aReadr[pMerger->aTree[1]].pFd==0);
}
return (rc==SQLITE_OK ? pTask->pUnpacked->errCode : rc);
}
#if SQLITE_MAX_WORKER_THREADS>0
/*
** The main routine for background threads that write level-0 PMAs.
*/
static void *vdbeSorterFlushThread(void *pCtx){
SortSubtask *pTask = (SortSubtask*)pCtx;
int rc; /* Return code */
assert( pTask->bDone==0 );
rc = vdbeSorterListToPMA(pTask, &pTask->list);
pTask->bDone = 1;
return SQLITE_INT_TO_PTR(rc);
}
#endif /* SQLITE_MAX_WORKER_THREADS>0 */
/*
** Flush the current contents of VdbeSorter.list to a new PMA, possibly
** using a background thread.
*/
static int vdbeSorterFlushPMA(VdbeSorter *pSorter){
#if SQLITE_MAX_WORKER_THREADS==0
pSorter->bUsePMA = 1;
return vdbeSorterListToPMA(&pSorter->aTask[0], &pSorter->list);
#else
int rc = SQLITE_OK;
int i;
SortSubtask *pTask = 0; /* Thread context used to create new PMA */
int nWorker = (pSorter->nTask-1);
/* Set the flag to indicate that at least one PMA has been written.
** Or will be, anyhow. */
pSorter->bUsePMA = 1;
/* Select a sub-task to sort and flush the current list of in-memory
** records to disk. If the sorter is running in multi-threaded mode,
** round-robin between the first (pSorter->nTask-1) tasks. Except, if
** the background thread from a sub-tasks previous turn is still running,
** skip it. If the first (pSorter->nTask-1) sub-tasks are all still busy,
** fall back to using the final sub-task. The first (pSorter->nTask-1)
** sub-tasks are prefered as they use background threads - the final
** sub-task uses the main thread. */
for(i=0; i<nWorker; i++){
int iTest = (pSorter->iPrev + i + 1) % nWorker;
pTask = &pSorter->aTask[iTest];
if( pTask->bDone ){
rc = vdbeSorterJoinThread(pTask);
}
if( rc!=SQLITE_OK || pTask->pThread==0 ) break;
}
if( rc==SQLITE_OK ){
if( i==nWorker ){
/* Use the foreground thread for this operation */
rc = vdbeSorterListToPMA(&pSorter->aTask[nWorker], &pSorter->list);
}else{
/* Launch a background thread for this operation */
u8 *aMem = pTask->list.aMemory;
void *pCtx = (void*)pTask;
assert( pTask->pThread==0 && pTask->bDone==0 );
assert( pTask->list.pList==0 );
assert( pTask->list.aMemory==0 || pSorter->list.aMemory!=0 );
pSorter->iPrev = (u8)(pTask - pSorter->aTask);
pTask->list = pSorter->list;
pSorter->list.pList = 0;
pSorter->list.szPMA = 0;
if( aMem ){
pSorter->list.aMemory = aMem;
pSorter->nMemory = sqlite3MallocSize(aMem);
}else if( pSorter->list.aMemory ){
pSorter->list.aMemory = sqlite3Malloc(pSorter->nMemory);
if( !pSorter->list.aMemory ) return SQLITE_NOMEM;
}
rc = vdbeSorterCreateThread(pTask, vdbeSorterFlushThread, pCtx);
}
}
return rc;
#endif /* SQLITE_MAX_WORKER_THREADS!=0 */
}
/*
** Add a record to the sorter.
*/
int sqlite3VdbeSorterWrite(
const VdbeCursor *pCsr, /* Sorter cursor */
Mem *pVal /* Memory cell containing record */
){
VdbeSorter *pSorter = pCsr->pSorter;
int rc = SQLITE_OK; /* Return Code */
SorterRecord *pNew; /* New list element */
int bFlush; /* True to flush contents of memory to PMA */
int nReq; /* Bytes of memory required */
int nPMA; /* Bytes of PMA space required */
int t; /* serial type of first record field */
getVarint32((const u8*)&pVal->z[1], t);
if( t>0 && t<10 && t!=7 ){
pSorter->typeMask &= SORTER_TYPE_INTEGER;
}else if( t>10 && (t & 0x01) ){
pSorter->typeMask &= SORTER_TYPE_TEXT;
}else{
pSorter->typeMask = 0;
}
assert( pSorter );
/* Figure out whether or not the current contents of memory should be
** flushed to a PMA before continuing. If so, do so.
**
** If using the single large allocation mode (pSorter->aMemory!=0), then
** flush the contents of memory to a new PMA if (a) at least one value is
** already in memory and (b) the new value will not fit in memory.
**
** Or, if using separate allocations for each record, flush the contents
** of memory to a PMA if either of the following are true:
**
** * The total memory allocated for the in-memory list is greater
** than (page-size * cache-size), or
**
** * The total memory allocated for the in-memory list is greater
** than (page-size * 10) and sqlite3HeapNearlyFull() returns true.
*/
nReq = pVal->n + sizeof(SorterRecord);
nPMA = pVal->n + sqlite3VarintLen(pVal->n);
if( pSorter->mxPmaSize ){
if( pSorter->list.aMemory ){
bFlush = pSorter->iMemory && (pSorter->iMemory+nReq) > pSorter->mxPmaSize;
}else{
bFlush = (
(pSorter->list.szPMA > pSorter->mxPmaSize)
|| (pSorter->list.szPMA > pSorter->mnPmaSize && sqlite3HeapNearlyFull())
);
}
if( bFlush ){
rc = vdbeSorterFlushPMA(pSorter);
pSorter->list.szPMA = 0;
pSorter->iMemory = 0;
assert( rc!=SQLITE_OK || pSorter->list.pList==0 );
}
}
pSorter->list.szPMA += nPMA;
if( nPMA>pSorter->mxKeysize ){
pSorter->mxKeysize = nPMA;
}
if( pSorter->list.aMemory ){
int nMin = pSorter->iMemory + nReq;
if( nMin>pSorter->nMemory ){
u8 *aNew;
int nNew = pSorter->nMemory * 2;
while( nNew < nMin ) nNew = nNew*2;
if( nNew > pSorter->mxPmaSize ) nNew = pSorter->mxPmaSize;
if( nNew < nMin ) nNew = nMin;
aNew = sqlite3Realloc(pSorter->list.aMemory, nNew);
if( !aNew ) return SQLITE_NOMEM;
pSorter->list.pList = (SorterRecord*)(
aNew + ((u8*)pSorter->list.pList - pSorter->list.aMemory)
);
pSorter->list.aMemory = aNew;
pSorter->nMemory = nNew;
}
pNew = (SorterRecord*)&pSorter->list.aMemory[pSorter->iMemory];
pSorter->iMemory += ROUND8(nReq);
pNew->u.iNext = (int)((u8*)(pSorter->list.pList) - pSorter->list.aMemory);
}else{
pNew = (SorterRecord *)sqlite3Malloc(nReq);
if( pNew==0 ){
return SQLITE_NOMEM;
}
pNew->u.pNext = pSorter->list.pList;
}
memcpy(SRVAL(pNew), pVal->z, pVal->n);
pNew->nVal = pVal->n;
pSorter->list.pList = pNew;
return rc;
}
/*
** Read keys from pIncr->pMerger and populate pIncr->aFile[1]. The format
** of the data stored in aFile[1] is the same as that used by regular PMAs,
** except that the number-of-bytes varint is omitted from the start.
*/
static int vdbeIncrPopulate(IncrMerger *pIncr){
int rc = SQLITE_OK;
int rc2;
i64 iStart = pIncr->iStartOff;
SorterFile *pOut = &pIncr->aFile[1];
SortSubtask *pTask = pIncr->pTask;
MergeEngine *pMerger = pIncr->pMerger;
PmaWriter writer;
assert( pIncr->bEof==0 );
vdbeSorterPopulateDebug(pTask, "enter");
vdbePmaWriterInit(pOut->pFd, &writer, pTask->pSorter->pgsz, iStart);
while( rc==SQLITE_OK ){
int dummy;
PmaReader *pReader = &pMerger->aReadr[ pMerger->aTree[1] ];
int nKey = pReader->nKey;
i64 iEof = writer.iWriteOff + writer.iBufEnd;
/* Check if the output file is full or if the input has been exhausted.
** In either case exit the loop. */
if( pReader->pFd==0 ) break;
if( (iEof + nKey + sqlite3VarintLen(nKey))>(iStart + pIncr->mxSz) ) break;
/* Write the next key to the output. */
vdbePmaWriteVarint(&writer, nKey);
vdbePmaWriteBlob(&writer, pReader->aKey, nKey);
assert( pIncr->pMerger->pTask==pTask );
rc = vdbeMergeEngineStep(pIncr->pMerger, &dummy);
}
rc2 = vdbePmaWriterFinish(&writer, &pOut->iEof);
if( rc==SQLITE_OK ) rc = rc2;
vdbeSorterPopulateDebug(pTask, "exit");
return rc;
}
#if SQLITE_MAX_WORKER_THREADS>0
/*
** The main routine for background threads that populate aFile[1] of
** multi-threaded IncrMerger objects.
*/
static void *vdbeIncrPopulateThread(void *pCtx){
IncrMerger *pIncr = (IncrMerger*)pCtx;
void *pRet = SQLITE_INT_TO_PTR( vdbeIncrPopulate(pIncr) );
pIncr->pTask->bDone = 1;
return pRet;
}
/*
** Launch a background thread to populate aFile[1] of pIncr.
*/
static int vdbeIncrBgPopulate(IncrMerger *pIncr){
void *p = (void*)pIncr;
assert( pIncr->bUseThread );
return vdbeSorterCreateThread(pIncr->pTask, vdbeIncrPopulateThread, p);
}
#endif
/*
** This function is called when the PmaReader corresponding to pIncr has
** finished reading the contents of aFile[0]. Its purpose is to "refill"
** aFile[0] such that the PmaReader should start rereading it from the
** beginning.
**
** For single-threaded objects, this is accomplished by literally reading
** keys from pIncr->pMerger and repopulating aFile[0].
**
** For multi-threaded objects, all that is required is to wait until the
** background thread is finished (if it is not already) and then swap
** aFile[0] and aFile[1] in place. If the contents of pMerger have not
** been exhausted, this function also launches a new background thread
** to populate the new aFile[1].
**
** SQLITE_OK is returned on success, or an SQLite error code otherwise.
*/
static int vdbeIncrSwap(IncrMerger *pIncr){
int rc = SQLITE_OK;
#if SQLITE_MAX_WORKER_THREADS>0
if( pIncr->bUseThread ){
rc = vdbeSorterJoinThread(pIncr->pTask);
if( rc==SQLITE_OK ){
SorterFile f0 = pIncr->aFile[0];
pIncr->aFile[0] = pIncr->aFile[1];
pIncr->aFile[1] = f0;
}
if( rc==SQLITE_OK ){
if( pIncr->aFile[0].iEof==pIncr->iStartOff ){
pIncr->bEof = 1;
}else{
rc = vdbeIncrBgPopulate(pIncr);
}
}
}else
#endif
{
rc = vdbeIncrPopulate(pIncr);
pIncr->aFile[0] = pIncr->aFile[1];
if( pIncr->aFile[0].iEof==pIncr->iStartOff ){
pIncr->bEof = 1;
}
}
return rc;
}
/*
** Allocate and return a new IncrMerger object to read data from pMerger.
**
** If an OOM condition is encountered, return NULL. In this case free the
** pMerger argument before returning.
*/
static int vdbeIncrMergerNew(
SortSubtask *pTask, /* The thread that will be using the new IncrMerger */
MergeEngine *pMerger, /* The MergeEngine that the IncrMerger will control */
IncrMerger **ppOut /* Write the new IncrMerger here */
){
int rc = SQLITE_OK;
IncrMerger *pIncr = *ppOut = (IncrMerger*)
(sqlite3FaultSim(100) ? 0 : sqlite3MallocZero(sizeof(*pIncr)));
if( pIncr ){
pIncr->pMerger = pMerger;
pIncr->pTask = pTask;
pIncr->mxSz = MAX(pTask->pSorter->mxKeysize+9,pTask->pSorter->mxPmaSize/2);
pTask->file2.iEof += pIncr->mxSz;
}else{
vdbeMergeEngineFree(pMerger);
rc = SQLITE_NOMEM;
}
return rc;
}
#if SQLITE_MAX_WORKER_THREADS>0
/*
** Set the "use-threads" flag on object pIncr.
*/
static void vdbeIncrMergerSetThreads(IncrMerger *pIncr){
pIncr->bUseThread = 1;
pIncr->pTask->file2.iEof -= pIncr->mxSz;
}
#endif /* SQLITE_MAX_WORKER_THREADS>0 */
/*
** Recompute pMerger->aTree[iOut] by comparing the next keys on the
** two PmaReaders that feed that entry. Neither of the PmaReaders
** are advanced. This routine merely does the comparison.
*/
static void vdbeMergeEngineCompare(
MergeEngine *pMerger, /* Merge engine containing PmaReaders to compare */
int iOut /* Store the result in pMerger->aTree[iOut] */
){
int i1;
int i2;
int iRes;
PmaReader *p1;
PmaReader *p2;
assert( iOut<pMerger->nTree && iOut>0 );
if( iOut>=(pMerger->nTree/2) ){
i1 = (iOut - pMerger->nTree/2) * 2;
i2 = i1 + 1;
}else{
i1 = pMerger->aTree[iOut*2];
i2 = pMerger->aTree[iOut*2+1];
}
p1 = &pMerger->aReadr[i1];
p2 = &pMerger->aReadr[i2];
if( p1->pFd==0 ){
iRes = i2;
}else if( p2->pFd==0 ){
iRes = i1;
}else{
SortSubtask *pTask = pMerger->pTask;
int bCached = 0;
int res;
assert( pTask->pUnpacked!=0 ); /* from vdbeSortSubtaskMain() */
res = pTask->xCompare(
pTask, &bCached, p1->aKey, p1->nKey, p2->aKey, p2->nKey
);
if( res<=0 ){
iRes = i1;
}else{
iRes = i2;
}
}
pMerger->aTree[iOut] = iRes;
}
/*
** Allowed values for the eMode parameter to vdbeMergeEngineInit()
** and vdbePmaReaderIncrMergeInit().
**
** Only INCRINIT_NORMAL is valid in single-threaded builds (when
** SQLITE_MAX_WORKER_THREADS==0). The other values are only used
** when there exists one or more separate worker threads.
*/
#define INCRINIT_NORMAL 0
#define INCRINIT_TASK 1
#define INCRINIT_ROOT 2
/* Forward reference.
** The vdbeIncrMergeInit() and vdbePmaReaderIncrMergeInit() routines call each
** other (when building a merge tree).
*/
static int vdbePmaReaderIncrMergeInit(PmaReader *pReadr, int eMode);
/*
** Initialize the MergeEngine object passed as the second argument. Once this
** function returns, the first key of merged data may be read from the
** MergeEngine object in the usual fashion.
**
** If argument eMode is INCRINIT_ROOT, then it is assumed that any IncrMerge
** objects attached to the PmaReader objects that the merger reads from have
** already been populated, but that they have not yet populated aFile[0] and
** set the PmaReader objects up to read from it. In this case all that is
** required is to call vdbePmaReaderNext() on each PmaReader to point it at
** its first key.
**
** Otherwise, if eMode is any value other than INCRINIT_ROOT, then use
** vdbePmaReaderIncrMergeInit() to initialize each PmaReader that feeds data
** to pMerger.
**
** SQLITE_OK is returned if successful, or an SQLite error code otherwise.
*/
static int vdbeMergeEngineInit(
SortSubtask *pTask, /* Thread that will run pMerger */
MergeEngine *pMerger, /* MergeEngine to initialize */
int eMode /* One of the INCRINIT_XXX constants */
){
int rc = SQLITE_OK; /* Return code */
int i; /* For looping over PmaReader objects */
int nTree = pMerger->nTree;
/* eMode is always INCRINIT_NORMAL in single-threaded mode */
assert( SQLITE_MAX_WORKER_THREADS>0 || eMode==INCRINIT_NORMAL );
/* Verify that the MergeEngine is assigned to a single thread */
assert( pMerger->pTask==0 );
pMerger->pTask = pTask;
for(i=0; i<nTree; i++){
if( SQLITE_MAX_WORKER_THREADS>0 && eMode==INCRINIT_ROOT ){
/* PmaReaders should be normally initialized in order, as if they are
** reading from the same temp file this makes for more linear file IO.
** However, in the INCRINIT_ROOT case, if PmaReader aReadr[nTask-1] is
** in use it will block the vdbePmaReaderNext() call while it uses
** the main thread to fill its buffer. So calling PmaReaderNext()
** on this PmaReader before any of the multi-threaded PmaReaders takes
** better advantage of multi-processor hardware. */
rc = vdbePmaReaderNext(&pMerger->aReadr[nTree-i-1]);
}else{
rc = vdbePmaReaderIncrMergeInit(&pMerger->aReadr[i], INCRINIT_NORMAL);
}
if( rc!=SQLITE_OK ) return rc;
}
for(i=pMerger->nTree-1; i>0; i--){
vdbeMergeEngineCompare(pMerger, i);
}
return pTask->pUnpacked->errCode;
}
/*
** Initialize the IncrMerge field of a PmaReader.
**
** If the PmaReader passed as the first argument is not an incremental-reader
** (if pReadr->pIncr==0), then this function is a no-op. Otherwise, it serves
** to open and/or initialize the temp file related fields of the IncrMerge
** object at (pReadr->pIncr).
**
** If argument eMode is set to INCRINIT_NORMAL, then all PmaReaders
** in the sub-tree headed by pReadr are also initialized. Data is then loaded
** into the buffers belonging to pReadr and it is set to
** point to the first key in its range.
**
** If argument eMode is set to INCRINIT_TASK, then pReadr is guaranteed
** to be a multi-threaded PmaReader and this function is being called in a
** background thread. In this case all PmaReaders in the sub-tree are
** initialized as for INCRINIT_NORMAL and the aFile[1] buffer belonging to
** pReadr is populated. However, pReadr itself is not set up to point
** to its first key. A call to vdbePmaReaderNext() is still required to do
** that.
**
** The reason this function does not call vdbePmaReaderNext() immediately
** in the INCRINIT_TASK case is that vdbePmaReaderNext() assumes that it has
** to block on thread (pTask->thread) before accessing aFile[1]. But, since
** this entire function is being run by thread (pTask->thread), that will
** lead to the current background thread attempting to join itself.
**
** Finally, if argument eMode is set to INCRINIT_ROOT, it may be assumed
** that pReadr->pIncr is a multi-threaded IncrMerge objects, and that all
** child-trees have already been initialized using IncrInit(INCRINIT_TASK).
** In this case vdbePmaReaderNext() is called on all child PmaReaders and
** the current PmaReader set to point to the first key in its range.
**
** SQLITE_OK is returned if successful, or an SQLite error code otherwise.
*/
static int vdbePmaReaderIncrMergeInit(PmaReader *pReadr, int eMode){
int rc = SQLITE_OK;
IncrMerger *pIncr = pReadr->pIncr;
/* eMode is always INCRINIT_NORMAL in single-threaded mode */
assert( SQLITE_MAX_WORKER_THREADS>0 || eMode==INCRINIT_NORMAL );
if( pIncr ){
SortSubtask *pTask = pIncr->pTask;
sqlite3 *db = pTask->pSorter->db;
rc = vdbeMergeEngineInit(pTask, pIncr->pMerger, eMode);
/* Set up the required files for pIncr. A multi-theaded IncrMerge object
** requires two temp files to itself, whereas a single-threaded object
** only requires a region of pTask->file2. */
if( rc==SQLITE_OK ){
int mxSz = pIncr->mxSz;
#if SQLITE_MAX_WORKER_THREADS>0
if( pIncr->bUseThread ){
rc = vdbeSorterOpenTempFile(db, mxSz, &pIncr->aFile[0].pFd);
if( rc==SQLITE_OK ){
rc = vdbeSorterOpenTempFile(db, mxSz, &pIncr->aFile[1].pFd);
}
}else
#endif
/*if( !pIncr->bUseThread )*/{
if( pTask->file2.pFd==0 ){
assert( pTask->file2.iEof>0 );
rc = vdbeSorterOpenTempFile(db, pTask->file2.iEof, &pTask->file2.pFd);
pTask->file2.iEof = 0;
}
if( rc==SQLITE_OK ){
pIncr->aFile[1].pFd = pTask->file2.pFd;
pIncr->iStartOff = pTask->file2.iEof;
pTask->file2.iEof += mxSz;
}
}
}
#if SQLITE_MAX_WORKER_THREADS>0
if( rc==SQLITE_OK && pIncr->bUseThread ){
/* Use the current thread to populate aFile[1], even though this
** PmaReader is multi-threaded. The reason being that this function
** is already running in background thread pIncr->pTask->thread. */
assert( eMode==INCRINIT_ROOT || eMode==INCRINIT_TASK );
rc = vdbeIncrPopulate(pIncr);
}
#endif
if( rc==SQLITE_OK
&& (SQLITE_MAX_WORKER_THREADS==0 || eMode!=INCRINIT_TASK)
){
rc = vdbePmaReaderNext(pReadr);
}
}
return rc;
}
#if SQLITE_MAX_WORKER_THREADS>0
/*
** The main routine for vdbePmaReaderIncrMergeInit() operations run in
** background threads.
*/
static void *vdbePmaReaderBgInit(void *pCtx){
PmaReader *pReader = (PmaReader*)pCtx;
void *pRet = SQLITE_INT_TO_PTR(
vdbePmaReaderIncrMergeInit(pReader,INCRINIT_TASK)
);
pReader->pIncr->pTask->bDone = 1;
return pRet;
}
/*
** Use a background thread to invoke vdbePmaReaderIncrMergeInit(INCRINIT_TASK)
** on the PmaReader object passed as the first argument.
**
** This call will initialize the various fields of the pReadr->pIncr
** structure and, if it is a multi-threaded IncrMerger, launch a
** background thread to populate aFile[1].
*/
static int vdbePmaReaderBgIncrInit(PmaReader *pReadr){
void *pCtx = (void*)pReadr;
return vdbeSorterCreateThread(pReadr->pIncr->pTask, vdbePmaReaderBgInit, pCtx);
}
#endif
/*
** Allocate a new MergeEngine object to merge the contents of nPMA level-0
** PMAs from pTask->file. If no error occurs, set *ppOut to point to
** the new object and return SQLITE_OK. Or, if an error does occur, set *ppOut
** to NULL and return an SQLite error code.
**
** When this function is called, *piOffset is set to the offset of the
** first PMA to read from pTask->file. Assuming no error occurs, it is
** set to the offset immediately following the last byte of the last
** PMA before returning. If an error does occur, then the final value of
** *piOffset is undefined.
*/
static int vdbeMergeEngineLevel0(
SortSubtask *pTask, /* Sorter task to read from */
int nPMA, /* Number of PMAs to read */
i64 *piOffset, /* IN/OUT: Readr offset in pTask->file */
MergeEngine **ppOut /* OUT: New merge-engine */
){
MergeEngine *pNew; /* Merge engine to return */
i64 iOff = *piOffset;
int i;
int rc = SQLITE_OK;
*ppOut = pNew = vdbeMergeEngineNew(nPMA);
if( pNew==0 ) rc = SQLITE_NOMEM;
for(i=0; i<nPMA && rc==SQLITE_OK; i++){
i64 nDummy;
PmaReader *pReadr = &pNew->aReadr[i];
rc = vdbePmaReaderInit(pTask, &pTask->file, iOff, pReadr, &nDummy);
iOff = pReadr->iEof;
}
if( rc!=SQLITE_OK ){
vdbeMergeEngineFree(pNew);
*ppOut = 0;
}
*piOffset = iOff;
return rc;
}
/*
** Return the depth of a tree comprising nPMA PMAs, assuming a fanout of
** SORTER_MAX_MERGE_COUNT. The returned value does not include leaf nodes.
**
** i.e.
**
** nPMA<=16 -> TreeDepth() == 0
** nPMA<=256 -> TreeDepth() == 1
** nPMA<=65536 -> TreeDepth() == 2
*/
static int vdbeSorterTreeDepth(int nPMA){
int nDepth = 0;
i64 nDiv = SORTER_MAX_MERGE_COUNT;
while( nDiv < (i64)nPMA ){
nDiv = nDiv * SORTER_MAX_MERGE_COUNT;
nDepth++;
}
return nDepth;
}
/*
** pRoot is the root of an incremental merge-tree with depth nDepth (according
** to vdbeSorterTreeDepth()). pLeaf is the iSeq'th leaf to be added to the
** tree, counting from zero. This function adds pLeaf to the tree.
**
** If successful, SQLITE_OK is returned. If an error occurs, an SQLite error
** code is returned and pLeaf is freed.
*/
static int vdbeSorterAddToTree(
SortSubtask *pTask, /* Task context */
int nDepth, /* Depth of tree according to TreeDepth() */
int iSeq, /* Sequence number of leaf within tree */
MergeEngine *pRoot, /* Root of tree */
MergeEngine *pLeaf /* Leaf to add to tree */
){
int rc = SQLITE_OK;
int nDiv = 1;
int i;
MergeEngine *p = pRoot;
IncrMerger *pIncr;
rc = vdbeIncrMergerNew(pTask, pLeaf, &pIncr);
for(i=1; i<nDepth; i++){
nDiv = nDiv * SORTER_MAX_MERGE_COUNT;
}
for(i=1; i<nDepth && rc==SQLITE_OK; i++){
int iIter = (iSeq / nDiv) % SORTER_MAX_MERGE_COUNT;
PmaReader *pReadr = &p->aReadr[iIter];
if( pReadr->pIncr==0 ){
MergeEngine *pNew = vdbeMergeEngineNew(SORTER_MAX_MERGE_COUNT);
if( pNew==0 ){
rc = SQLITE_NOMEM;
}else{
rc = vdbeIncrMergerNew(pTask, pNew, &pReadr->pIncr);
}
}
if( rc==SQLITE_OK ){
p = pReadr->pIncr->pMerger;
nDiv = nDiv / SORTER_MAX_MERGE_COUNT;
}
}
if( rc==SQLITE_OK ){
p->aReadr[iSeq % SORTER_MAX_MERGE_COUNT].pIncr = pIncr;
}else{
vdbeIncrFree(pIncr);
}
return rc;
}
/*
** This function is called as part of a SorterRewind() operation on a sorter
** that has already written two or more level-0 PMAs to one or more temp
** files. It builds a tree of MergeEngine/IncrMerger/PmaReader objects that
** can be used to incrementally merge all PMAs on disk.
**
** If successful, SQLITE_OK is returned and *ppOut set to point to the
** MergeEngine object at the root of the tree before returning. Or, if an
** error occurs, an SQLite error code is returned and the final value
** of *ppOut is undefined.
*/
static int vdbeSorterMergeTreeBuild(
VdbeSorter *pSorter, /* The VDBE cursor that implements the sort */
MergeEngine **ppOut /* Write the MergeEngine here */
){
MergeEngine *pMain = 0;
int rc = SQLITE_OK;
int iTask;
#if SQLITE_MAX_WORKER_THREADS>0
/* If the sorter uses more than one task, then create the top-level
** MergeEngine here. This MergeEngine will read data from exactly
** one PmaReader per sub-task. */
assert( pSorter->bUseThreads || pSorter->nTask==1 );
if( pSorter->nTask>1 ){
pMain = vdbeMergeEngineNew(pSorter->nTask);
if( pMain==0 ) rc = SQLITE_NOMEM;
}
#endif
for(iTask=0; rc==SQLITE_OK && iTask<pSorter->nTask; iTask++){
SortSubtask *pTask = &pSorter->aTask[iTask];
assert( pTask->nPMA>0 || SQLITE_MAX_WORKER_THREADS>0 );
if( SQLITE_MAX_WORKER_THREADS==0 || pTask->nPMA ){
MergeEngine *pRoot = 0; /* Root node of tree for this task */
int nDepth = vdbeSorterTreeDepth(pTask->nPMA);
i64 iReadOff = 0;
if( pTask->nPMA<=SORTER_MAX_MERGE_COUNT ){
rc = vdbeMergeEngineLevel0(pTask, pTask->nPMA, &iReadOff, &pRoot);
}else{
int i;
int iSeq = 0;
pRoot = vdbeMergeEngineNew(SORTER_MAX_MERGE_COUNT);
if( pRoot==0 ) rc = SQLITE_NOMEM;
for(i=0; i<pTask->nPMA && rc==SQLITE_OK; i += SORTER_MAX_MERGE_COUNT){
MergeEngine *pMerger = 0; /* New level-0 PMA merger */
int nReader; /* Number of level-0 PMAs to merge */
nReader = MIN(pTask->nPMA - i, SORTER_MAX_MERGE_COUNT);
rc = vdbeMergeEngineLevel0(pTask, nReader, &iReadOff, &pMerger);
if( rc==SQLITE_OK ){
rc = vdbeSorterAddToTree(pTask, nDepth, iSeq++, pRoot, pMerger);
}
}
}
if( rc==SQLITE_OK ){
#if SQLITE_MAX_WORKER_THREADS>0
if( pMain!=0 ){
rc = vdbeIncrMergerNew(pTask, pRoot, &pMain->aReadr[iTask].pIncr);
}else
#endif
{
assert( pMain==0 );
pMain = pRoot;
}
}else{
vdbeMergeEngineFree(pRoot);
}
}
}
if( rc!=SQLITE_OK ){
vdbeMergeEngineFree(pMain);
pMain = 0;
}
*ppOut = pMain;
return rc;
}
/*
** This function is called as part of an sqlite3VdbeSorterRewind() operation
** on a sorter that has written two or more PMAs to temporary files. It sets
** up either VdbeSorter.pMerger (for single threaded sorters) or pReader
** (for multi-threaded sorters) so that it can be used to iterate through
** all records stored in the sorter.
**
** SQLITE_OK is returned if successful, or an SQLite error code otherwise.
*/
static int vdbeSorterSetupMerge(VdbeSorter *pSorter){
int rc; /* Return code */
SortSubtask *pTask0 = &pSorter->aTask[0];
MergeEngine *pMain = 0;
#if SQLITE_MAX_WORKER_THREADS
sqlite3 *db = pTask0->pSorter->db;
int i;
SorterCompare xCompare = vdbeSorterGetCompare(pSorter);
for(i=0; i<pSorter->nTask; i++){
pSorter->aTask[i].xCompare = xCompare;
}
#endif
rc = vdbeSorterMergeTreeBuild(pSorter, &pMain);
if( rc==SQLITE_OK ){
#if SQLITE_MAX_WORKER_THREADS
assert( pSorter->bUseThreads==0 || pSorter->nTask>1 );
if( pSorter->bUseThreads ){
int iTask;
PmaReader *pReadr = 0;
SortSubtask *pLast = &pSorter->aTask[pSorter->nTask-1];
rc = vdbeSortAllocUnpacked(pLast);
if( rc==SQLITE_OK ){
pReadr = (PmaReader*)sqlite3DbMallocZero(db, sizeof(PmaReader));
pSorter->pReader = pReadr;
if( pReadr==0 ) rc = SQLITE_NOMEM;
}
if( rc==SQLITE_OK ){
rc = vdbeIncrMergerNew(pLast, pMain, &pReadr->pIncr);
if( rc==SQLITE_OK ){
vdbeIncrMergerSetThreads(pReadr->pIncr);
for(iTask=0; iTask<(pSorter->nTask-1); iTask++){
IncrMerger *pIncr;
if( (pIncr = pMain->aReadr[iTask].pIncr) ){
vdbeIncrMergerSetThreads(pIncr);
assert( pIncr->pTask!=pLast );
}
}
for(iTask=0; rc==SQLITE_OK && iTask<pSorter->nTask; iTask++){
PmaReader *p = &pMain->aReadr[iTask];
assert( p->pIncr==0 || p->pIncr->pTask==&pSorter->aTask[iTask] );
if( p->pIncr ){
if( iTask==pSorter->nTask-1 ){
rc = vdbePmaReaderIncrMergeInit(p, INCRINIT_TASK);
}else{
rc = vdbePmaReaderBgIncrInit(p);
}
}
}
}
pMain = 0;
}
if( rc==SQLITE_OK ){
rc = vdbePmaReaderIncrMergeInit(pReadr, INCRINIT_ROOT);
}
}else
#endif
{
rc = vdbeMergeEngineInit(pTask0, pMain, INCRINIT_NORMAL);
pSorter->pMerger = pMain;
pMain = 0;
}
}
if( rc!=SQLITE_OK ){
vdbeMergeEngineFree(pMain);
}
return rc;
}
/*
** Once the sorter has been populated by calls to sqlite3VdbeSorterWrite,
** this function is called to prepare for iterating through the records
** in sorted order.
*/
int sqlite3VdbeSorterRewind(const VdbeCursor *pCsr, int *pbEof){
VdbeSorter *pSorter = pCsr->pSorter;
int rc = SQLITE_OK; /* Return code */
assert( pSorter );
/* If no data has been written to disk, then do not do so now. Instead,
** sort the VdbeSorter.pRecord list. The vdbe layer will read data directly
** from the in-memory list. */
if( pSorter->bUsePMA==0 ){
if( pSorter->list.pList ){
*pbEof = 0;
rc = vdbeSorterSort(&pSorter->aTask[0], &pSorter->list);
}else{
*pbEof = 1;
}
return rc;
}
/* Write the current in-memory list to a PMA. When the VdbeSorterWrite()
** function flushes the contents of memory to disk, it immediately always
** creates a new list consisting of a single key immediately afterwards.
** So the list is never empty at this point. */
assert( pSorter->list.pList );
rc = vdbeSorterFlushPMA(pSorter);
/* Join all threads */
rc = vdbeSorterJoinAll(pSorter, rc);
vdbeSorterRewindDebug("rewind");
/* Assuming no errors have occurred, set up a merger structure to
** incrementally read and merge all remaining PMAs. */
assert( pSorter->pReader==0 );
if( rc==SQLITE_OK ){
rc = vdbeSorterSetupMerge(pSorter);
*pbEof = 0;
}
vdbeSorterRewindDebug("rewinddone");
return rc;
}
/*
** Advance to the next element in the sorter.
*/
int sqlite3VdbeSorterNext(sqlite3 *db, const VdbeCursor *pCsr, int *pbEof){
VdbeSorter *pSorter = pCsr->pSorter;
int rc; /* Return code */
assert( pSorter->bUsePMA || (pSorter->pReader==0 && pSorter->pMerger==0) );
if( pSorter->bUsePMA ){
assert( pSorter->pReader==0 || pSorter->pMerger==0 );
assert( pSorter->bUseThreads==0 || pSorter->pReader );
assert( pSorter->bUseThreads==1 || pSorter->pMerger );
#if SQLITE_MAX_WORKER_THREADS>0
if( pSorter->bUseThreads ){
rc = vdbePmaReaderNext(pSorter->pReader);
*pbEof = (pSorter->pReader->pFd==0);
}else
#endif
/*if( !pSorter->bUseThreads )*/ {
assert( pSorter->pMerger!=0 );
assert( pSorter->pMerger->pTask==(&pSorter->aTask[0]) );
rc = vdbeMergeEngineStep(pSorter->pMerger, pbEof);
}
}else{
SorterRecord *pFree = pSorter->list.pList;
pSorter->list.pList = pFree->u.pNext;
pFree->u.pNext = 0;
if( pSorter->list.aMemory==0 ) vdbeSorterRecordFree(db, pFree);
*pbEof = !pSorter->list.pList;
rc = SQLITE_OK;
}
return rc;
}
/*
** Return a pointer to a buffer owned by the sorter that contains the
** current key.
*/
static void *vdbeSorterRowkey(
const VdbeSorter *pSorter, /* Sorter object */
int *pnKey /* OUT: Size of current key in bytes */
){
void *pKey;
if( pSorter->bUsePMA ){
PmaReader *pReader;
#if SQLITE_MAX_WORKER_THREADS>0
if( pSorter->bUseThreads ){
pReader = pSorter->pReader;
}else
#endif
/*if( !pSorter->bUseThreads )*/{
pReader = &pSorter->pMerger->aReadr[pSorter->pMerger->aTree[1]];
}
*pnKey = pReader->nKey;
pKey = pReader->aKey;
}else{
*pnKey = pSorter->list.pList->nVal;
pKey = SRVAL(pSorter->list.pList);
}
return pKey;
}
/*
** Copy the current sorter key into the memory cell pOut.
*/
int sqlite3VdbeSorterRowkey(const VdbeCursor *pCsr, Mem *pOut){
VdbeSorter *pSorter = pCsr->pSorter;
void *pKey; int nKey; /* Sorter key to copy into pOut */
pKey = vdbeSorterRowkey(pSorter, &nKey);
if( sqlite3VdbeMemClearAndResize(pOut, nKey) ){
return SQLITE_NOMEM;
}
pOut->n = nKey;
MemSetTypeFlag(pOut, MEM_Blob);
memcpy(pOut->z, pKey, nKey);
return SQLITE_OK;
}
/*
** Compare the key in memory cell pVal with the key that the sorter cursor
** passed as the first argument currently points to. For the purposes of
** the comparison, ignore the rowid field at the end of each record.
**
** If the sorter cursor key contains any NULL values, consider it to be
** less than pVal. Even if pVal also contains NULL values.
**
** If an error occurs, return an SQLite error code (i.e. SQLITE_NOMEM).
** Otherwise, set *pRes to a negative, zero or positive value if the
** key in pVal is smaller than, equal to or larger than the current sorter
** key.
**
** This routine forms the core of the OP_SorterCompare opcode, which in
** turn is used to verify uniqueness when constructing a UNIQUE INDEX.
*/
int sqlite3VdbeSorterCompare(
const VdbeCursor *pCsr, /* Sorter cursor */
Mem *pVal, /* Value to compare to current sorter key */
int nKeyCol, /* Compare this many columns */
int *pRes /* OUT: Result of comparison */
){
VdbeSorter *pSorter = pCsr->pSorter;
UnpackedRecord *r2 = pSorter->pUnpacked;
KeyInfo *pKeyInfo = pCsr->pKeyInfo;
int i;
void *pKey; int nKey; /* Sorter key to compare pVal with */
if( r2==0 ){
char *p;
r2 = pSorter->pUnpacked = sqlite3VdbeAllocUnpackedRecord(pKeyInfo,0,0,&p);
assert( pSorter->pUnpacked==(UnpackedRecord*)p );
if( r2==0 ) return SQLITE_NOMEM;
r2->nField = nKeyCol;
}
assert( r2->nField==nKeyCol );
pKey = vdbeSorterRowkey(pSorter, &nKey);
sqlite3VdbeRecordUnpack(pKeyInfo, nKey, pKey, r2);
for(i=0; i<nKeyCol; i++){
if( r2->aMem[i].flags & MEM_Null ){
*pRes = -1;
return SQLITE_OK;
}
}
*pRes = sqlite3VdbeRecordCompare(pVal->n, pVal->z, r2);
return SQLITE_OK;
}