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If the OP_NullRow opcode is given a cursor that has not yet been opened,

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then go automatically open it to a special pseudo-cursor that allows returns
NULL for every column.  Used by the new RIGHT JOIN implementation.

FossilOrigin-Name: 4526c5d316508093b7f3aeda1ce9d16ceb0be79842015a6d51f28c22b4473ca2
This commit is contained in:
drh
2022-04-13 17:41:03 +00:00
parent f7ecd956ce
commit 3ac624344d
3 changed files with 19 additions and 13 deletions
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18
src/vdbe.c
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@@ -2714,10 +2714,9 @@ op_column_restart:
if( pC->cacheStatus!=p->cacheCtr ){ /*OPTIMIZATION-IF-FALSE*/
if( pC->nullRow ){
if( pC->eCurType==CURTYPE_PSEUDO ){
if( pC->eCurType==CURTYPE_PSEUDO && pC->seekResult>0 ){
/* For the special case of as pseudo-cursor, the seekResult field
** identifies the register that holds the record */
assert( pC->seekResult>0 );
pReg = &aMem[pC->seekResult];
assert( pReg->flags & MEM_Blob );
assert( memIsValid(pReg) );
@@ -5802,16 +5801,23 @@ case OP_Rowid: { /* out2 */
** that occur while the cursor is on the null row will always
** write a NULL.
**
** Or, if P1 is a Pseudo-Cursor (a cursor opened using OP_OpenPseudo)
** just reset the cache for that cursor. This causes the row of
** content held by the pseudo-cursor to be reparsed.
** If cursor P1 is not previously opened, open it now to a special
** pseudo-cursor that always returns NULL for every column.
*/
case OP_NullRow: {
VdbeCursor *pC;
assert( pOp->p1>=0 && pOp->p1<p->nCursor );
pC = p->apCsr[pOp->p1];
assert( pC!=0 );
if( pC==0 ){
/* If the cursor is not already open, create a special kind of
** pseudo-cursor that always gives null rows. */
pC = allocateCursor(p, pOp->p1, 1, CURTYPE_PSEUDO);
if( pC==0 ) goto no_mem;
pC->seekResult = 0;
pC->isTable = 1;
pC->uc.pCursor = sqlite3BtreeFakeValidCursor();
}
pC->nullRow = 1;
pC->cacheStatus = CACHE_STALE;
if( pC->eCurType==CURTYPE_BTREE ){