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Overview
| Comment: | A new implementation for the sqlite3ExprImpliesExpr() theorem prover that does a better job of answering TRUE to "(NOT A) OR B" when B is a NOT NULL expression. |
|---|---|
| Downloads: | Tarball | ZIP archive |
| Timelines: | family | ancestors | descendants | both | trunk |
| Files: | files | file ages | folders |
| SHA3-256: |
b3413197f57711f04102d8cc6ff1e8dd |
| User & Date: | drh 2019-05-11 19:36:03.376 |
Context
|
2019-05-13
| ||
| 11:52 | Fix an assert() failure in fts5 that could occur when processing a corrupt database. (check-in: f158c048be user: dan tags: trunk) | |
|
2019-05-11
| ||
| 19:36 | A new implementation for the sqlite3ExprImpliesExpr() theorem prover that does a better job of answering TRUE to "(NOT A) OR B" when B is a NOT NULL expression. (check-in: b3413197f5 user: drh tags: trunk) | |
| 16:14 | When considering partial indexes, do not assume that a "CASE x ..." expression implies "x IS NOT NULL". (check-in: 1b24303220 user: dan tags: trunk) | |
Changes
Changes to src/expr.c.
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*/
int sqlite3ExprCompareSkip(Expr *pA, Expr *pB, int iTab){
return sqlite3ExprCompare(0,
sqlite3ExprSkipCollate(pA),
sqlite3ExprSkipCollate(pB),
iTab);
}
/*
** 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
** be false. Examples:
**
** pE1: x==5 pE2: x==5 Result: true
| > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > | 4903 4904 4905 4906 4907 4908 4909 4910 4911 4912 4913 4914 4915 4916 4917 4918 4919 4920 4921 4922 4923 4924 4925 4926 4927 4928 4929 4930 4931 4932 4933 4934 4935 4936 4937 4938 4939 4940 4941 4942 4943 4944 4945 4946 4947 4948 4949 4950 4951 4952 4953 4954 4955 4956 4957 4958 4959 4960 4961 4962 4963 4964 4965 4966 4967 4968 4969 4970 4971 4972 4973 4974 4975 4976 4977 4978 4979 4980 4981 4982 4983 4984 4985 4986 |
*/
int sqlite3ExprCompareSkip(Expr *pA, Expr *pB, int iTab){
return sqlite3ExprCompare(0,
sqlite3ExprSkipCollate(pA),
sqlite3ExprSkipCollate(pB),
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
** be false. Examples:
**
** pE1: x==5 pE2: x==5 Result: true
|
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if( pE2->op==TK_OR
&& (sqlite3ExprImpliesExpr(pParse, pE1, pE2->pLeft, iTab)
|| sqlite3ExprImpliesExpr(pParse, pE1, pE2->pRight, iTab) )
){
return 1;
}
if( pE2->op==TK_NOTNULL
| | < < < < < < | | 5010 5011 5012 5013 5014 5015 5016 5017 5018 5019 5020 5021 5022 5023 5024 5025 5026 |
if( pE2->op==TK_OR
&& (sqlite3ExprImpliesExpr(pParse, pE1, pE2->pLeft, iTab)
|| sqlite3ExprImpliesExpr(pParse, pE1, pE2->pRight, iTab) )
){
return 1;
}
if( pE2->op==TK_NOTNULL
&& exprImpliesNotNull(pParse, pE1, pE2->pLeft, iTab, 0)
){
return 1;
}
return 0;
}
/*
** This is the Expr node callback for sqlite3ExprImpliesNotNullRow().
** If the expression node requires that the table at pWalker->iCur
|
| ︙ | ︙ |