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Overview
Comment:Add header comments on new routines. Rework the sqlite3Stat4Column() routine so that is (in theory) able to deal with corrupt samples.
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Timelines: family | ancestors | descendants | both | stat4-skipscan
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SHA1: ef5cdf949bb53a2958fa34e176b4b9eeda269de5
User & Date: drh 2014-06-28 16:06:44
Context
2014-06-28
17:35
Add further tests to skipscan5.test. check-in: 4b8230e8 user: dan tags: stat4-skipscan
16:06
Add header comments on new routines. Rework the sqlite3Stat4Column() routine so that is (in theory) able to deal with corrupt samples. check-in: ef5cdf94 user: drh tags: stat4-skipscan
15:26
Fix a problem with using stat4 samples of type text when estimating the rows visited by a range-query/skip-scan loop. check-in: dfb09db6 user: dan tags: stat4-skipscan
Changes
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Changes to src/vdbemem.c.

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  FuncDefHash *pHash = &GLOBAL(FuncDefHash, sqlite3GlobalFunctions);
  FuncDef *aFunc = (FuncDef*)&GLOBAL(FuncDef, aAnalyzeTableFuncs);
  for(i=0; i<ArraySize(aAnalyzeTableFuncs); i++){
    sqlite3FuncDefInsert(pHash, &aFunc[i]);
  }
}



















static int stat4ValueFromExpr(
  Parse *pParse,                  /* Parse context */
  Expr *pExpr,                    /* The expression to extract a value from */
  u8 affinity,                    /* Affinity to use */
  struct ValueNewStat4Ctx *pAlloc,/* How to allocate space */
  sqlite3_value **ppVal           /* OUT: New value object (or NULL) */
){
  int rc = SQLITE_OK;
  sqlite3_value *pVal = 0;
  sqlite3 *db = pParse->db;

  /* Skip over any TK_COLLATE nodes */
................................................................................
  Expr *pExpr,                    /* The expression to extract a value from */
  u8 affinity,                    /* Affinity to use */
  sqlite3_value **ppVal           /* OUT: New value object (or NULL) */
){
  return stat4ValueFromExpr(pParse, pExpr, affinity, 0, ppVal);
}









int sqlite3Stat4Column(
  sqlite3 *db,                    /* Database handle */
  const void *pRec,               /* Pointer to buffer containing record */
  int nRec,                       /* Size of buffer pRec in bytes */
  int iCol,                       /* Column to extract */
  sqlite3_value **ppVal           /* OUT: Extracted value */
){
  int rc = SQLITE_OK;
  Mem *pMem = *ppVal;
  if( pMem==0 ){
    pMem = (Mem*)sqlite3ValueNew(db);
    if( pMem==0 ){
      rc = SQLITE_NOMEM;
    }
  }

  if( rc==SQLITE_OK ){
    u32 t;
    int nHdr;
    int iHdr;
    int iField;
    int i;
    u8 *a = (u8*)pRec;

    iHdr = getVarint32(a, nHdr);
    iField = nHdr;
    for(i=0; i<iCol; i++){
      iHdr += getVarint32(&a[iHdr], t);
      iField += sqlite3VdbeSerialTypeLen(t);
    }

    iHdr = getVarint32(&a[iHdr], t);
    pMem->enc = ENC(db);
    sqlite3VdbeSerialGet(&a[iField], t, pMem);
  }

  *ppVal = pMem;
  return rc;
}

/*
** Unless it is NULL, the argument must be an UnpackedRecord object returned
** by an earlier call to sqlite3Stat4ProbeSetValue(). This call deletes
** the object.
*/







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  FuncDefHash *pHash = &GLOBAL(FuncDefHash, sqlite3GlobalFunctions);
  FuncDef *aFunc = (FuncDef*)&GLOBAL(FuncDef, aAnalyzeTableFuncs);
  for(i=0; i<ArraySize(aAnalyzeTableFuncs); i++){
    sqlite3FuncDefInsert(pHash, &aFunc[i]);
  }
}

/*
** Attempt to extract a value from pExpr and use it to construct *ppVal.
**
** If pAlloc is not NULL, then an UnpackedRecord object is created for
** pAlloc if one does not exist and the new value is added to the
** UnpackedRecord object.
**
** A value is extracted in the following cases:
**
**  * (pExpr==0). In this case the value is assumed to be an SQL NULL,
**
**  * The expression is a bound variable, and this is a reprepare, or
**
**  * The expression is a literal value.
**
** On success, *ppVal is made to point to the extracted value.  The caller
** is responsible for ensuring that the value is eventually freed.
*/
static int stat4ValueFromExpr(
  Parse *pParse,                  /* Parse context */
  Expr *pExpr,                    /* The expression to extract a value from */
  u8 affinity,                    /* Affinity to use */
  struct ValueNewStat4Ctx *pAlloc,/* How to allocate space.  Or NULL */
  sqlite3_value **ppVal           /* OUT: New value object (or NULL) */
){
  int rc = SQLITE_OK;
  sqlite3_value *pVal = 0;
  sqlite3 *db = pParse->db;

  /* Skip over any TK_COLLATE nodes */
................................................................................
  Expr *pExpr,                    /* The expression to extract a value from */
  u8 affinity,                    /* Affinity to use */
  sqlite3_value **ppVal           /* OUT: New value object (or NULL) */
){
  return stat4ValueFromExpr(pParse, pExpr, affinity, 0, ppVal);
}

/*
** Extract the iCol-th column from the nRec-byte record in pRec.  Write
** the column value into *ppVal.  If *ppVal is initially NULL then a new
** sqlite3_value object is allocated.
**
** If *ppVal is initially NULL then the caller is responsible for 
** ensuring that the value written into *ppVal is eventually freed.
*/
int sqlite3Stat4Column(
  sqlite3 *db,                    /* Database handle */
  const void *pRec,               /* Pointer to buffer containing record */
  int nRec,                       /* Size of buffer pRec in bytes */
  int iCol,                       /* Column to extract */
  sqlite3_value **ppVal           /* OUT: Extracted value */
){
  u32 t;                          /* a column type code */
  int nHdr;                       /* Size of the header in the record */
  int iHdr;                       /* Next unread header byte */
  int iField;                     /* Next unread data byte */
  int szField;                    /* Size of the current data field */
  int i;                          /* Column index */
  u8 *a = (u8*)pRec;              /* Typecast byte array */
  Mem *pMem = *ppVal;             /* Write result into this Mem object */

  assert( iCol>0 );
  iHdr = getVarint32(a, nHdr);
  if( nHdr>nRec || iHdr>=nHdr ) return SQLITE_CORRUPT_BKPT;
  iField = nHdr;
  for(i=0; i<=iCol; i++){
    iHdr += getVarint32(&a[iHdr], t);
    testcase( iHdr==nHdr );
    testcase( iHdr==nHdr+1 );
    if( iHdr>nHdr ) return SQLITE_CORRUPT_BKPT;
    szField = sqlite3VdbeSerialTypeLen(t);
    iField += szField;
  }
  testcase( iField==nRec );
  testcase( iField==nRec+1 );
  if( iField>nRec ) return SQLITE_CORRUPT_BKPT;
  if( pMem==0 ){
    pMem = *ppVal = sqlite3ValueNew(db);
    if( pMem==0 ) return SQLITE_NOMEM;
  }
  sqlite3VdbeSerialGet(&a[iField-szField], t, pMem);
  pMem->enc = ENC(db);
  return SQLITE_OK;
}

/*
** Unless it is NULL, the argument must be an UnpackedRecord object returned
** by an earlier call to sqlite3Stat4ProbeSetValue(). This call deletes
** the object.
*/