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| author | drh <drh@noemail.net> | 2009-11-11 00:24:31 +0000 |
|---|---|---|
| committer | drh <drh@noemail.net> | 2009-11-11 00:24:31 +0000 |
| commit | ae6bb9570b6d6ef7893a9571d0fa10b43d936f61 (patch) | |
| tree | 5c9ee74af1b3a4dc9d4912d51af98525357395ae /src/func.c | |
| parent | 63b38789210cab605cbff76932f4be20323a5724 (diff) | |
| download | sqlite-ae6bb9570b6d6ef7893a9571d0fa10b43d936f61.tar.gz sqlite-ae6bb9570b6d6ef7893a9571d0fa10b43d936f61.zip | |
Generate VDBE code for the built-in COALESCE() and IFNULL() functions. This
allows unused arguments to never be evaluated, which is a performance win when
the unused argument is a subquery.
FossilOrigin-Name: 30055b257c3c65f8123cad5ac6c62c4c6ca2c900
Diffstat (limited to 'src/func.c')
| -rw-r--r-- | src/func.c | 16 |
1 files changed, 14 insertions, 2 deletions
diff --git a/src/func.c b/src/func.c index 2766fa3b1..980d04edb 100644 --- a/src/func.c +++ b/src/func.c @@ -335,6 +335,14 @@ static void lowerFunc(sqlite3_context *context, int argc, sqlite3_value **argv){ } } + +#if 0 /* This function is never used. */ +/* +** The COALESCE() and IFNULL() functions used to be implemented as shown +** here. But now they are implemented as VDBE code so that unused arguments +** do not have to be computed. This legacy implementation is retained as +** comment. +*/ /* ** Implementation of the IFNULL(), NVL(), and COALESCE() functions. ** All three do the same thing. They return the first non-NULL @@ -353,6 +361,8 @@ static void ifnullFunc( } } } +#endif /* NOT USED */ +#define ifnullFunc versionFunc /* Substitute function - never called */ /* ** Implementation of random(). Return a random integer. @@ -1437,10 +1447,12 @@ void sqlite3RegisterGlobalFunctions(void){ FUNCTION(upper, 1, 0, 0, upperFunc ), FUNCTION(lower, 1, 0, 0, lowerFunc ), FUNCTION(coalesce, 1, 0, 0, 0 ), - FUNCTION(coalesce, -1, 0, 0, ifnullFunc ), FUNCTION(coalesce, 0, 0, 0, 0 ), +/* FUNCTION(coalesce, -1, 0, 0, ifnullFunc ), */ + {-1,SQLITE_UTF8,SQLITE_FUNC_COALESCE,0,0,ifnullFunc,0,0,"coalesce",0}, FUNCTION(hex, 1, 0, 0, hexFunc ), - FUNCTION(ifnull, 2, 0, 1, ifnullFunc ), +/* FUNCTION(ifnull, 2, 0, 0, ifnullFunc ), */ + {2,SQLITE_UTF8,SQLITE_FUNC_COALESCE,0,0,ifnullFunc,0,0,"ifnull",0}, FUNCTION(random, 0, 0, 0, randomFunc ), FUNCTION(randomblob, 1, 0, 0, randomBlob ), FUNCTION(nullif, 2, 0, 1, nullifFunc ), |