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Experimental attempt to make better use of covering indexes within OR queries.

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FossilOrigin-Name: a323ac3a9d42bd5cb38d724c7e1180584b91054c
This commit is contained in:
dan
2016-01-29 19:29:45 +00:00
parent 65875f37bc
commit de892d9660
7 changed files with 121 additions and 22 deletions
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50
src/wherecode.c
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@@ -746,6 +746,54 @@ static void codeCursorHint(
# define codeCursorHint(A,B,C) /* No-op */
#endif /* SQLITE_ENABLE_CURSOR_HINTS */
/*
** Cursor iCur is open on an intkey b-tree (a table). Register iRowid contains
** a rowid value just read from cursor iIdxCur, open on index pIdx. This
** function generates code to do a deferred seek of cursor iCur to the
** rowid stored in register iRowid.
**
** Normally, this is just:
**
** OP_Seek $iCur $iRowid
**
** However, if the scan currently being coded is a branch of an OR-loop and
** the statement currently being coded is a SELECT, then P3 of the OP_Seek
** is set to iIdxCur and P4 is set to point to an array of integers
** containing one entry for each column of the table cursor iCur is open
** on. For each table column, if the column is the i'th column of the
** index, then the corresponding array entry is set to (i+1). If the column
** does not appear in the index at all, the array entry is set to 0.
*/
static void codeDeferredSeek(
WhereInfo *pWInfo, /* Where clause context */
Index *pIdx, /* Index scan is using */
int iCur, /* Cursor for IPK b-tree */
int iRowid, /* Register containing rowid to seek to */
int iIdxCur /* Index cursor */
){
Parse *pParse = pWInfo->pParse; /* Parse context */
Vdbe *v = pParse->pVdbe; /* Vdbe to generate code within */
assert( iIdxCur>0 );
assert( pIdx->aiColumn[pIdx->nColumn-1]==-1 );
sqlite3VdbeAddOp3(v, OP_Seek, iCur, iRowid, iIdxCur);
if( (pWInfo->wctrlFlags & WHERE_FORCE_TABLE)
&& sqlite3ParseToplevel(pParse)->writeMask==0
){
int i;
Table *pTab = pIdx->pTable;
int *ai = (int*)sqlite3DbMallocZero(pParse->db, sizeof(int) * pTab->nCol);
if( ai ){
for(i=0; i<pIdx->nColumn-1; i++){
assert( pIdx->aiColumn[i]<pTab->nCol );
if( pIdx->aiColumn[i]>=0 ) ai[pIdx->aiColumn[i]] = i+1;
}
sqlite3VdbeChangeP4(v, -1, (char*)ai, P4_INTARRAY);
}
}
}
/*
** Generate code for the start of the iLevel-th loop in the WHERE clause
** implementation described by pWInfo.
@@ -1232,7 +1280,7 @@ Bitmask sqlite3WhereCodeOneLoopStart(
sqlite3VdbeAddOp3(v, OP_NotExists, iCur, 0, iRowidReg);
VdbeCoverage(v);
}else{
sqlite3VdbeAddOp2(v, OP_Seek, iCur, iRowidReg); /* Deferred seek */
codeDeferredSeek(pWInfo, pIdx, iCur, iRowidReg, iIdxCur);
}
}else if( iCur!=iIdxCur ){
Index *pPk = sqlite3PrimaryKeyIndex(pIdx->pTable);