diff options
Diffstat (limited to 'src/expr.c')
-rw-r--r-- | src/expr.c | 65 |
1 files changed, 65 insertions, 0 deletions
diff --git a/src/expr.c b/src/expr.c index a5e5edd32..db74e8759 100644 --- a/src/expr.c +++ b/src/expr.c @@ -1259,6 +1259,71 @@ int sqlite3ExprIsInteger(Expr *p, int *pValue){ } /* +** Return FALSE if there is no chance that the expression can be NULL. +** +** If the expression might be NULL or if the expression is too complex +** to tell return TRUE. +** +** This routine is used as an optimization, to skip OP_IsNull opcodes +** when we know that a value cannot be NULL. Hence, a false positive +** (returning TRUE when in fact the expression can never be NULL) might +** be a small performance hit but is otherwise harmless. On the other +** hand, a false negative (returning FALSE when the result could be NULL) +** will likely result in an incorrect answer. So when in doubt, return +** TRUE. +*/ +int sqlite3ExprCanBeNull(const Expr *p){ + u8 op; + while( p->op==TK_UPLUS || p->op==TK_MINUS ){ p = p->pLeft; } + op = p->op; + if( op==TK_REGISTER ) op = p->op2; + switch( op ){ + case TK_INTEGER: + case TK_STRING: + case TK_FLOAT: + case TK_BLOB: + return 0; + default: + return 1; + } +} + +/* +** Return TRUE if the given expression is a constant which would be +** unchanged by OP_Affinity with the affinity given in the second +** argument. +** +** This routine is used to determine if the OP_Affinity operation +** can be omitted. When in doubt return FALSE. A false negative +** is harmless. A false positive, however, can result in the wrong +** answer. +*/ +int sqlite3ExprNeedsNoAffinityChange(const Expr *p, char aff){ + u8 op; + if( aff==SQLITE_AFF_NONE ) return 1; + while( p->op==TK_UPLUS || p->op==TK_MINUS ){ p = p->pLeft; } + op = p->op; + if( op==TK_REGISTER ) op = p->op2; + switch( op ){ + case TK_INTEGER: { + return aff==SQLITE_AFF_INTEGER || aff==SQLITE_AFF_NUMERIC; + } + case TK_FLOAT: { + return aff==SQLITE_AFF_REAL || aff==SQLITE_AFF_NUMERIC; + } + case TK_STRING: { + return aff==SQLITE_AFF_TEXT; + } + case TK_BLOB: { + return 1; + } + default: { + return 0; + } + } +} + +/* ** Return TRUE if the given string is a row-id column name. */ int sqlite3IsRowid(const char *z){ |