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Better comment to describe the confusing operand reversal for infix

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functions. (CVS 3325)

FossilOrigin-Name: 30dfb9bf2131370fe57e000495f5c292d392a010
This commit is contained in:
drh
2006-07-08 18:41:37 +00:00
parent 6a03a1c5f7
commit a43fa22771
3 changed files with 20 additions and 15 deletions
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21
src/expr.c
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@@ -12,7 +12,7 @@
** This file contains routines used for analyzing expressions and
** for generating VDBE code that evaluates expressions in SQLite.
**
** $Id: expr.c,v 1.264 2006/07/08 18:35:00 drh Exp $
** $Id: expr.c,v 1.265 2006/07/08 18:41:37 drh Exp $
*/
#include "sqliteInt.h"
#include <ctype.h>
@@ -1675,16 +1675,21 @@ void sqlite3ExprCode(Parse *pParse, Expr *pExpr){
assert( pDef!=0 );
nExpr = sqlite3ExprCodeExprList(pParse, pList);
#ifndef SQLITE_OMIT_VIRTUALTABLE
/* Possibly overload the function if the first argument is
** a virtual table column.
**
** For infix functions (LIKE, GLOB, REGEXP, and MATCH) use the
** second argument, not the first, as the argument to test to
** see if it is a column in a virtual table. This is done because
** the left operand of infix functions (the operand we want to
** control overloading) ends up as the second argument to the
** function. The expression "A glob B" is equivalent to
** "glob(B,A). We want to use the A in "A glob B" to test
** for function overloading. But we use the B term in "glob(B,A)".
*/
if( nExpr>=2 && (pExpr->flags & EP_InfixFunc) ){
/* For infix functions GLOB, LIKE, REGEXP, and MATCH, check
** the second argument to the function which is operand to
** left of the function name. Users normally consider the
** left operand to be the first argument, even though it is
** really the second argument to the underlying function. */
pDef = sqlite3VtabOverloadFunction(pDef, nExpr, pList->a[1].pExpr);
}else if( nExpr>0 ){
/* For normal functions, go by the first argument - the first
** argument after the "(" that follows the function name */
pDef = sqlite3VtabOverloadFunction(pDef, nExpr, pList->a[0].pExpr);
}
#endif