Improved detection and handling of NULL values on the RHS of a IN operator.
FossilOrigin-Name: 468e730036edac22cfeb9ea3515aa16e6bcd6650
diff --git a/src/expr.c b/src/expr.c
index 591ea98..6440dea 100644
--- a/src/expr.c
+++ b/src/expr.c
@@ -1476,6 +1476,22 @@
}
/*
+** Generate code that checks the single-column index table iCur to see if
+** contains any NULL entries. Cause the register at regHasNull to be set
+** to a non-NULL value if iCur contains no NULLs. Cause register regHasNull
+** to be set to NULL if iCur contains one or more NULL values.
+*/
+static void sqlite3SetHasNullFlag(Vdbe *v, int iCur, int regHasNull){
+ int j1;
+ sqlite3VdbeAddOp2(v, OP_Integer, 0, regHasNull);
+ j1 = sqlite3VdbeAddOp1(v, OP_Rewind, iCur); VdbeCoverage(v);
+ sqlite3VdbeAddOp3(v, OP_Column, iCur, 0, regHasNull);
+ sqlite3VdbeChangeP5(v, OPFLAG_TYPEOFARG);
+ VdbeComment((v, "<maybe-NULL?>"));
+ sqlite3VdbeJumpHere(v, j1);
+}
+
+/*
** This function is used by the implementation of the IN (...) operator.
** The pX parameter is the expression on the RHS of the IN operator, which
** might be either a list of expressions or a subquery.
@@ -1532,24 +1548,9 @@
** NULL value, then *prRhsHasNull is left unchanged.
**
** If a register is allocated and its location stored in *prRhsHasNull, then
-** the value in that register will be:
-**
-** 0 if the (...) contains no NULL values
-** 1 if the (...) does not contain NULL values
-** NULL if we do not yet know if (...) contains NULLs
-**
-** If the (...) does not remain constant for the duration of the query
-** (i.e. the SELECT within the (...) is a correlated subquery) then the
-** value of the allocated register is reset to NULL each time the subquery
-** is rerun. This allows the caller to use vdbe code equivalent to the
-** following:
-**
-** if( r[*prRhsHasNull] IS NULL ){
-** r[*prRhsHasNull] = <test if data structure contains null>
-** }
-**
-** in order to avoid running the <test if data structure contains null>
-** test more often than is necessary.
+** the value in that register will be NULL if the b-tree contains one or more
+** NULL values, and it will be some non-NULL value if the b-tree contains no
+** NULL values.
*/
#ifndef SQLITE_OMIT_SUBQUERY
int sqlite3FindInIndex(Parse *pParse, Expr *pX, u32 inFlags, int *prRhsHasNull){
@@ -1628,7 +1629,7 @@
if( prRhsHasNull && !pTab->aCol[iCol].notNull ){
*prRhsHasNull = ++pParse->nMem;
- sqlite3VdbeAddOp2(v, OP_Null, 0, *prRhsHasNull);
+ sqlite3SetHasNullFlag(v, iTab, *prRhsHasNull);
}
sqlite3VdbeJumpHere(v, iAddr);
}
@@ -1691,10 +1692,10 @@
int sqlite3CodeSubselect(
Parse *pParse, /* Parsing context */
Expr *pExpr, /* The IN, SELECT, or EXISTS operator */
- int rMayHaveNull, /* Register that records whether NULLs exist in RHS */
+ int rHasNullFlag, /* Register that records whether NULLs exist in RHS */
int isRowid /* If true, LHS of IN operator is a rowid */
){
- int testAddr = -1; /* One-time test address */
+ int jmpIfDynamic = -1; /* One-time test address */
int rReg = 0; /* Register storing resulting */
Vdbe *v = sqlite3GetVdbe(pParse);
if( NEVER(v==0) ) return 0;
@@ -1711,13 +1712,13 @@
** save the results, and reuse the same result on subsequent invocations.
*/
if( !ExprHasProperty(pExpr, EP_VarSelect) ){
- testAddr = sqlite3CodeOnce(pParse); VdbeCoverage(v);
+ jmpIfDynamic = sqlite3CodeOnce(pParse); VdbeCoverage(v);
}
#ifndef SQLITE_OMIT_EXPLAIN
if( pParse->explain==2 ){
char *zMsg = sqlite3MPrintf(
- pParse->db, "EXECUTE %s%s SUBQUERY %d", testAddr>=0?"":"CORRELATED ",
+ pParse->db, "EXECUTE %s%s SUBQUERY %d", jmpIfDynamic>=0?"":"CORRELATED ",
pExpr->op==TK_IN?"LIST":"SCALAR", pParse->iNextSelectId
);
sqlite3VdbeAddOp4(v, OP_Explain, pParse->iSelectId, 0, 0, zMsg, P4_DYNAMIC);
@@ -1731,10 +1732,6 @@
Expr *pLeft = pExpr->pLeft; /* the LHS of the IN operator */
KeyInfo *pKeyInfo = 0; /* Key information */
- if( rMayHaveNull ){
- sqlite3VdbeAddOp2(v, OP_Null, 0, rMayHaveNull);
- }
-
affinity = sqlite3ExprAffinity(pLeft);
/* Whether this is an 'x IN(SELECT...)' or an 'x IN(<exprlist>)'
@@ -1817,9 +1814,9 @@
** this code only executes once. Because for a non-constant
** expression we need to rerun this code each time.
*/
- if( testAddr>=0 && !sqlite3ExprIsConstant(pE2) ){
- sqlite3VdbeChangeToNoop(v, testAddr);
- testAddr = -1;
+ if( jmpIfDynamic>=0 && !sqlite3ExprIsConstant(pE2) ){
+ sqlite3VdbeChangeToNoop(v, jmpIfDynamic);
+ jmpIfDynamic = -1;
}
/* Evaluate the expression and insert it into the temp table */
@@ -1889,8 +1886,12 @@
}
}
- if( testAddr>=0 ){
- sqlite3VdbeJumpHere(v, testAddr);
+ if( rHasNullFlag ){
+ sqlite3SetHasNullFlag(v, pExpr->iTable, rHasNullFlag);
+ }
+
+ if( jmpIfDynamic>=0 ){
+ sqlite3VdbeJumpHere(v, jmpIfDynamic);
}
sqlite3ExprCachePop(pParse);
@@ -1911,7 +1912,7 @@
** if the LHS is NULL or if the LHS is not contained within the RHS and the
** RHS contains one or more NULL values.
**
-** This routine generates code will jump to destIfFalse if the LHS is not
+** This routine generates code that jumps to destIfFalse if the LHS is not
** contained within the RHS. If due to NULLs we cannot determine if the LHS
** is contained in the RHS then jump to destIfNull. If the LHS is contained
** within the RHS then fall through.
@@ -1997,34 +1998,19 @@
** the presence of a NULL on the RHS makes a difference in the
** outcome.
*/
- int j1, j2;
+ int j1;
/* First check to see if the LHS is contained in the RHS. If so,
- ** then the presence of NULLs in the RHS does not matter, so jump
- ** over all of the code that follows.
+ ** then the answer is TRUE the presence of NULLs in the RHS does
+ ** not matter. If the LHS is not contained in the RHS, then the
+ ** answer is NULL if the RHS contains NULLs and the answer is
+ ** FALSE if the RHS is NULL-free.
*/
j1 = sqlite3VdbeAddOp4Int(v, OP_Found, pExpr->iTable, 0, r1, 1);
VdbeCoverage(v);
-
- /* Here we begin generating code that runs if the LHS is not
- ** contained within the RHS. Generate additional code that
- ** tests the RHS for NULLs. If the RHS contains a NULL then
- ** jump to destIfNull. If there are no NULLs in the RHS then
- ** jump to destIfFalse.
- */
- sqlite3VdbeAddOp2(v, OP_If, rRhsHasNull, destIfNull); VdbeCoverage(v);
- sqlite3VdbeAddOp2(v, OP_IfNot, rRhsHasNull, destIfFalse); VdbeCoverage(v);
- j2 = sqlite3VdbeAddOp4Int(v, OP_Found, pExpr->iTable, 0, rRhsHasNull, 1);
+ sqlite3VdbeAddOp2(v, OP_IsNull, rRhsHasNull, destIfNull);
VdbeCoverage(v);
- sqlite3VdbeAddOp2(v, OP_Integer, 0, rRhsHasNull);
sqlite3VdbeAddOp2(v, OP_Goto, 0, destIfFalse);
- sqlite3VdbeJumpHere(v, j2);
- sqlite3VdbeAddOp2(v, OP_Integer, 1, rRhsHasNull);
- sqlite3VdbeAddOp2(v, OP_Goto, 0, destIfNull);
-
- /* The OP_Found at the top of this branch jumps here when true,
- ** causing the overall IN expression evaluation to fall through.
- */
sqlite3VdbeJumpHere(v, j1);
}
}