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Overview
Comment:Fix the ORDER BY optimization with IN constraints when the RHS of the IN constraint is a descending index.
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Timelines: family | ancestors | descendants | both | desc-orderby-fix-1
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SHA1: 62316ebaca933f7e5df2018e8360a2b74234f30a
User & Date: drh 2013-03-12 20:38:51
Context
2013-03-12
22:13
Fix a test case that had an ambiguous result. check-in: 38c6bddf user: drh tags: desc-orderby-fix-1
20:38
Fix the ORDER BY optimization with IN constraints when the RHS of the IN constraint is a descending index. check-in: 62316eba user: drh tags: desc-orderby-fix-1
18:49
Revise the patch to make it easier to understand. check-in: 3ce7eb02 user: drh tags: desc-orderby-fix-1
Changes
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Changes to src/expr.c.

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** all members of the RHS set, skipping duplicates.
**
** A cursor is opened on the b-tree object that the RHS of the IN operator
** and pX->iTable is set to the index of that cursor.
**
** The returned value of this function indicates the b-tree type, as follows:
**
**   IN_INDEX_ROWID - The cursor was opened on a database table.

**   IN_INDEX_INDEX - The cursor was opened on a database index.
**   IN_INDEX_EPH -   The cursor was opened on a specially created and
**                    populated epheremal table.
**
** An existing b-tree might be used if the RHS expression pX is a simple
** subquery such as:
**
**     SELECT <column> FROM <table>
**
** If the RHS of the IN operator is a list or a more complex subquery, then
................................................................................
  
          pKey = (char *)sqlite3IndexKeyinfo(pParse, pIdx);
          iAddr = sqlite3CodeOnce(pParse);
  
          sqlite3VdbeAddOp4(v, OP_OpenRead, iTab, pIdx->tnum, iDb,
                               pKey,P4_KEYINFO_HANDOFF);
          VdbeComment((v, "%s", pIdx->zName));

          eType = IN_INDEX_INDEX;

          sqlite3VdbeJumpHere(v, iAddr);
          if( prNotFound && !pTab->aCol[iCol].notNull ){
            *prNotFound = ++pParse->nMem;
            sqlite3VdbeAddOp2(v, OP_Null, 0, *prNotFound);
          }
        }







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** all members of the RHS set, skipping duplicates.
**
** A cursor is opened on the b-tree object that the RHS of the IN operator
** and pX->iTable is set to the index of that cursor.
**
** The returned value of this function indicates the b-tree type, as follows:
**
**   IN_INDEX_ROWID      - The cursor was opened on a database table.
**   IN_INDEX_INDEX_ASC  - The cursor was opened on an ascending index.
**   IN_INDEX_INDEX_DESC - The cursor was opened on a descending index.
**   IN_INDEX_EPH        - The cursor was opened on a specially created and
**                         populated epheremal table.
**
** An existing b-tree might be used if the RHS expression pX is a simple
** subquery such as:
**
**     SELECT <column> FROM <table>
**
** If the RHS of the IN operator is a list or a more complex subquery, then
................................................................................
  
          pKey = (char *)sqlite3IndexKeyinfo(pParse, pIdx);
          iAddr = sqlite3CodeOnce(pParse);
  
          sqlite3VdbeAddOp4(v, OP_OpenRead, iTab, pIdx->tnum, iDb,
                               pKey,P4_KEYINFO_HANDOFF);
          VdbeComment((v, "%s", pIdx->zName));
          assert( IN_INDEX_INDEX_DESC == IN_INDEX_INDEX_ASC+1 );
          eType = IN_INDEX_INDEX_ASC + pIdx->aSortOrder[0];

          sqlite3VdbeJumpHere(v, iAddr);
          if( prNotFound && !pTab->aCol[iCol].notNull ){
            *prNotFound = ++pParse->nMem;
            sqlite3VdbeAddOp2(v, OP_Null, 0, *prNotFound);
          }
        }

Changes to src/sqliteInt.h.

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#else
  #define sqlite3BeginBenignMalloc()
  #define sqlite3EndBenignMalloc()
#endif

#define IN_INDEX_ROWID           1
#define IN_INDEX_EPH             2
#define IN_INDEX_INDEX           3

int sqlite3FindInIndex(Parse *, Expr *, int*);

#ifdef SQLITE_ENABLE_ATOMIC_WRITE
  int sqlite3JournalOpen(sqlite3_vfs *, const char *, sqlite3_file *, int, int);
  int sqlite3JournalSize(sqlite3_vfs *);
  int sqlite3JournalCreate(sqlite3_file *);
  int sqlite3JournalExists(sqlite3_file *p);







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#else
  #define sqlite3BeginBenignMalloc()
  #define sqlite3EndBenignMalloc()
#endif

#define IN_INDEX_ROWID           1
#define IN_INDEX_EPH             2
#define IN_INDEX_INDEX_ASC       3
#define IN_INDEX_INDEX_DESC      4
int sqlite3FindInIndex(Parse *, Expr *, int*);

#ifdef SQLITE_ENABLE_ATOMIC_WRITE
  int sqlite3JournalOpen(sqlite3_vfs *, const char *, sqlite3_file *, int, int);
  int sqlite3JournalSize(sqlite3_vfs *);
  int sqlite3JournalCreate(sqlite3_file *);
  int sqlite3JournalExists(sqlite3_file *p);

Changes to src/where.c.

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    int iTab;
    struct InLoop *pIn;
    u8 bRev = (pLevel->plan.wsFlags & WHERE_REVERSE)!=0;

    if( (pLevel->plan.wsFlags & WHERE_INDEXED)!=0 
      && pLevel->plan.u.pIdx->aSortOrder[iEq]
    ){
      bRev = 1 - bRev;
    }
    assert( pX->op==TK_IN );
    iReg = iTarget;
    eType = sqlite3FindInIndex(pParse, pX, 0);

    iTab = pX->iTable;
    sqlite3VdbeAddOp2(v, bRev ? OP_Last : OP_Rewind, iTab, 0);
    assert( pLevel->plan.wsFlags & WHERE_IN_ABLE );
    if( pLevel->u.in.nIn==0 ){
      pLevel->addrNxt = sqlite3VdbeMakeLabel(v);
    }
    pLevel->u.in.nIn++;







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    int iTab;
    struct InLoop *pIn;
    u8 bRev = (pLevel->plan.wsFlags & WHERE_REVERSE)!=0;

    if( (pLevel->plan.wsFlags & WHERE_INDEXED)!=0 
      && pLevel->plan.u.pIdx->aSortOrder[iEq]
    ){
      bRev = !bRev;
    }
    assert( pX->op==TK_IN );
    iReg = iTarget;
    eType = sqlite3FindInIndex(pParse, pX, 0);
    if( eType==IN_INDEX_INDEX_DESC ) bRev = !bRev;
    iTab = pX->iTable;
    sqlite3VdbeAddOp2(v, bRev ? OP_Last : OP_Rewind, iTab, 0);
    assert( pLevel->plan.wsFlags & WHERE_IN_ABLE );
    if( pLevel->u.in.nIn==0 ){
      pLevel->addrNxt = sqlite3VdbeMakeLabel(v);
    }
    pLevel->u.in.nIn++;