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Simplifications to the SQLITE_KEEPNULL flag on VDBE comparison operators.

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FossilOrigin-Name: 96269f0179a7d8fa44ee278cef362962368c59ef
This commit is contained in:
drh
2016-09-05 15:02:41 +00:00
parent 083aefc732
commit 3fffbf9327
3 changed files with 22 additions and 12 deletions
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19
src/vdbe.c
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@@ -1912,7 +1912,8 @@ case OP_Cast: { /* in1 */
** the SQLITE_NULLEQ flag were omitted from P5.
**
** If both SQLITE_STOREP2 and SQLITE_KEEPNULL flags are set then the
** content of r[P2] is only set to 1 (true) if it was not previously NULL.
** content of r[P2] is only changed if the new value is NULL or 0 (false).
** In other words, a prior r[P2] value will not be overwritten by 1 (true).
*/
/* Opcode: Ne P1 P2 P3 P4 P5
** Synopsis: IF r[P3]!=r[P1]
@@ -1922,7 +1923,8 @@ case OP_Cast: { /* in1 */
** additional information.
**
** If both SQLITE_STOREP2 and SQLITE_KEEPNULL flags are set then the
** content of r[P2] is only set to 0 (false) if it was not previously NULL.
** content of r[P2] is only changed if the new value is NULL or 1 (true).
** In other words, a prior r[P2] value will not be overwritten by 0 (false).
*/
/* Opcode: Lt P1 P2 P3 P4 P5
** Synopsis: IF r[P3]<r[P1]
@@ -2086,11 +2088,20 @@ case OP_Ge: { /* same as TK_GE, jump, in1, in3 */
pOut = &aMem[pOp->p2];
iCompare = res;
res2 = res2!=0; /* For this path res2 must be exactly 0 or 1 */
if( (pOp->p5 & SQLITE_KEEPNULL)!=0 && (pOut->flags & MEM_Null)!=0 ){
if( (pOp->p5 & SQLITE_KEEPNULL)!=0 ){
/* The KEEPNULL flag prevents OP_Eq from overwriting a NULL with 1
** and prevents OP_Ne from overwriting NULL with 0. */
** and prevents OP_Ne from overwriting NULL with 0. This flag
** is only used in contexts where either:
** (1) op==OP_Eq && (r[P2]==NULL || r[P2]==0)
** (2) op==OP_Ne && (r[P2]==NULL || r[P2]==1)
** Therefore it is not necessary to check the content of r[P2] for
** NULL. */
assert( pOp->opcode==OP_Ne || pOp->opcode==OP_Eq );
assert( res2==0 || res2==1 );
testcase( res2==0 && pOp->opcode==OP_Eq );
testcase( res2==1 && pOp->opcode==OP_Eq );
testcase( res2==0 && pOp->opcode==OP_Ne );
testcase( res2==1 && pOp->opcode==OP_Ne );
if( (pOp->opcode==OP_Eq)==res2 ) break;
}
memAboutToChange(p, pOut);