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A new implementation for the sqlite3ExprImpliesExpr() theorem prover that

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does a better job of answering TRUE to "(NOT A) OR B" when B is a NOT NULL
expression.

FossilOrigin-Name: b3413197f57711f04102d8cc6ff1e8ddbe0f5f2bcb6e1989cf314fa97f0ff7f1
This commit is contained in:
drh 2019-05-11 19:36:03 +00:00
parent c6824c8d6c
commit c51cf8642f
3 changed files with 80 additions and 16 deletions
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14
manifest
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@ -1,5 +1,5 @@
C When\sconsidering\spartial\sindexes,\sdo\snot\sassume\sthat\sa\s"CASE\sx\s..."\sexpression\simplies\s"x\sIS\sNOT\sNULL".
D 2019-05-11T16:14:42.493
C A\snew\simplementation\sfor\sthe\ssqlite3ExprImpliesExpr()\stheorem\sprover\sthat\ndoes\sa\sbetter\sjob\sof\sanswering\sTRUE\sto\s"(NOT\sA)\sOR\sB"\swhen\sB\sis\sa\sNOT\sNULL\nexpression.
D 2019-05-11T19:36:03.376
F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
F LICENSE.md df5091916dbb40e6e9686186587125e1b2ff51f022cc334e886c19a0e9982724
@ -473,7 +473,7 @@ F src/date.c ebe1dc7c8a347117bb02570f1a931c62dd78f4a2b1b516f4837d45b7d6426957
F src/dbpage.c 135eb3b5e74f9ef74bde5cec2571192c90c86984fa534c88bf4a055076fa19b7
F src/dbstat.c c12833de69cb655751487d2c5a59607e36be1c58ba1f4bd536609909ad47b319
F src/delete.c d08c9e01a2664afd12edcfa3a9c6578517e8ff8735f35509582693adbe0edeaf
F src/expr.c de746e2fc5ee48441b1210fba9a39160981718430e6a75b3a2ba29a99957cb71
F src/expr.c a41e5a03d60e2d99a8eac1535f21258e3833b29a3f52789e76284d97b54bed5f
F src/fault.c 460f3e55994363812d9d60844b2a6de88826e007
F src/fkey.c 0e14d4bef8eac2d87bbd517e492d9084c65008d117823f8922c5e7b2b599bd33
F src/func.c 08d6d07d138735dd79f12a2b0c623d1dc9270d0eea61b8be584625391ef84475
@ -1825,7 +1825,7 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
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Z 5104434a3315d7327fcd08f55bb43328

2
manifest.uuid
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@ -1 +1 @@
1b24303220b7b4f59520176a0150fc619c668865450b4fdaa9ce4113a56e9687
b3413197f57711f04102d8cc6ff1e8ddbe0f5f2bcb6e1989cf314fa97f0ff7f1

80
src/expr.c
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@ -4908,6 +4908,76 @@ int sqlite3ExprCompareSkip(Expr *pA, Expr *pB, int iTab){
iTab);
}
/*
** Return non-zero if Expr p can only be true if pNN is not NULL.
*/
static int exprImpliesNotNull(
Parse *pParse, /* Parsing context */
Expr *p, /* The expression to be checked */
Expr *pNN, /* The expression that is NOT NULL */
int iTab, /* Table being evaluated */
int seenNot /* True if p is an operand of NOT */
){
assert( p );
assert( pNN );
if( sqlite3ExprCompare(pParse, p, pNN, iTab)==0 ) return 1;
switch( p->op ){
case TK_IN: {
if( seenNot && ExprHasProperty(p, EP_xIsSelect) ) return 0;
assert( ExprHasProperty(p,EP_xIsSelect)
|| (p->x.pList!=0 && p->x.pList->nExpr>0) );
return exprImpliesNotNull(pParse, p->pLeft, pNN, iTab, seenNot);
}
case TK_BETWEEN: {
ExprList *pList = p->x.pList;
assert( pList!=0 );
assert( pList->nExpr==2 );
if( seenNot ) return 0;
if( exprImpliesNotNull(pParse, pList->a[0].pExpr, pNN, iTab, seenNot)
|| exprImpliesNotNull(pParse, pList->a[1].pExpr, pNN, iTab, seenNot)
){
return 1;
}
return exprImpliesNotNull(pParse, p->pLeft, pNN, iTab, seenNot);
}
case TK_EQ:
case TK_NE:
case TK_LT:
case TK_LE:
case TK_GT:
case TK_GE:
case TK_PLUS:
case TK_MINUS:
case TK_STAR:
case TK_REM:
case TK_BITAND:
case TK_BITOR:
case TK_SLASH:
case TK_LSHIFT:
case TK_RSHIFT:
case TK_CONCAT: {
if( exprImpliesNotNull(pParse, p->pRight, pNN, iTab, seenNot) ) return 1;
/* Fall thru into the next case */
}
case TK_SPAN:
case TK_COLLATE:
case TK_BITNOT:
case TK_UPLUS:
case TK_UMINUS: {
return exprImpliesNotNull(pParse, p->pLeft, pNN, iTab, seenNot);
}
case TK_TRUTH: {
if( seenNot ) return 0;
if( p->op2!=TK_IS ) return 0;
return exprImpliesNotNull(pParse, p->pLeft, pNN, iTab, seenNot);
}
case TK_NOT: {
return exprImpliesNotNull(pParse, p->pLeft, pNN, iTab, 1);
}
}
return 0;
}
/*
** Return true if we can prove the pE2 will always be true if pE1 is
** true. Return false if we cannot complete the proof or if pE2 might
@ -4944,15 +5014,9 @@ int sqlite3ExprImpliesExpr(Parse *pParse, Expr *pE1, Expr *pE2, int iTab){
return 1;
}
if( pE2->op==TK_NOTNULL
&& pE1->op!=TK_ISNULL
&& pE1->op!=TK_IS
&& pE1->op!=TK_ISNOT
&& pE1->op!=TK_OR
&& pE1->op!=TK_CASE
&& exprImpliesNotNull(pParse, pE1, pE2->pLeft, iTab, 0)
){
Expr *pX = sqlite3ExprSkipCollate(pE1->pLeft);
testcase( pX!=pE1->pLeft );
if( sqlite3ExprCompare(pParse, pX, pE2->pLeft, iTab)==0 ) return 1;
return 1;
}
return 0;
}