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Use an ephemeral table rather than a RowSet to remember rowids in the

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two-pass UPDATE algorithm, as this uses much less memory for large UPDATEs.

FossilOrigin-Name: 842c432772e6cd8464cdb7bfdb38789adeea9aa9e0486d4034cc9841f085f517
This commit is contained in:
drh
2020-11-19 19:43:46 +00:00
parent 02e4b7d7df 32881bebbe
commit 5dc18e33ae
4 changed files with 33 additions and 18 deletions
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17
src/vdbe.c
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@@ -3901,7 +3901,7 @@ case OP_OpenDup: {
}
/* Opcode: OpenEphemeral P1 P2 * P4 P5
/* Opcode: OpenEphemeral P1 P2 P3 P4 P5
** Synopsis: nColumn=P2
**
** Open a new cursor P1 to a transient table.
@@ -3921,6 +3921,10 @@ case OP_OpenDup: {
** in btree.h. These flags control aspects of the operation of
** the btree. The BTREE_OMIT_JOURNAL and BTREE_SINGLE flags are
** added automatically.
**
** If P3 is positive, then reg[P3] is modified slightly so that it
** can be used as zero-length data for OP_Insert. This is an optimization
** that avoids an extra OP_Blob opcode to initialize that register.
*/
/* Opcode: OpenAutoindex P1 P2 * P4 *
** Synopsis: nColumn=P2
@@ -3943,6 +3947,15 @@ case OP_OpenEphemeral: {
SQLITE_OPEN_TRANSIENT_DB;
assert( pOp->p1>=0 );
assert( pOp->p2>=0 );
if( pOp->p3>0 ){
/* Make register reg[P3] into a value that can be used as the data
** form sqlite3BtreeInsert() where the length of the data is zero. */
assert( pOp->p2==0 ); /* Only used when number of columns is zero */
assert( pOp->opcode==OP_OpenEphemeral );
assert( aMem[pOp->p3].flags & MEM_Null );
aMem[pOp->p3].n = 0;
aMem[pOp->p3].z = "";
}
pCx = p->apCsr[pOp->p1];
if( pCx && pCx->pBtx ){
/* If the ephermeral table is already open, erase all existing content
@@ -5102,7 +5115,7 @@ case OP_Insert: {
if( pOp->p5 & OPFLAG_NCHANGE ) p->nChange++;
if( pOp->p5 & OPFLAG_LASTROWID ) db->lastRowid = x.nKey;
assert( pData->flags & (MEM_Blob|MEM_Str) );
assert( (pData->flags & (MEM_Blob|MEM_Str))!=0 || pData->n==0 );
x.pData = pData->z;
x.nData = pData->n;
seekResult = ((pOp->p5 & OPFLAG_USESEEKRESULT) ? pC->seekResult : 0);