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Performance optimization to the substr() SQL function.

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FossilOrigin-Name: ce228ce3d0132ad758b5b7464fcf22ae5976df3c02ec948280cc76290c79ed0b
This commit is contained in:
drh
2025-02-09 20:23:29 +00:00
parent 3bdebaeabb
commit 3efac4aa78
3 changed files with 19 additions and 20 deletions
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25
src/func.c
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@@ -356,11 +356,6 @@ static void substrFunc(
i64 p1, p2;
assert( argc==3 || argc==2 );
if( sqlite3_value_type(argv[1])==SQLITE_NULL
|| (argc==3 && sqlite3_value_type(argv[2])==SQLITE_NULL)
){
return;
}
p0type = sqlite3_value_type(argv[0]);
p1 = sqlite3_value_int64(argv[1]);
if( p0type==SQLITE_BLOB ){
@@ -378,19 +373,23 @@ static void substrFunc(
}
}
}
#ifdef SQLITE_SUBSTR_COMPATIBILITY
/* If SUBSTR_COMPATIBILITY is defined then substr(X,0,N) work the same as
** as substr(X,1,N) - it returns the first N characters of X. This
** is essentially a back-out of the bug-fix in check-in [5fc125d362df4b8]
** from 2009-02-02 for compatibility of applications that exploited the
** old buggy behavior. */
if( p1==0 ) p1 = 1; /* <rdar://problem/6778339> */
#endif
if( argc==3 ){
p2 = sqlite3_value_int64(argv[2]);
if( p2==0 && sqlite3_value_type(argv[2])==SQLITE_NULL ) return;
}else{
p2 = sqlite3_context_db_handle(context)->aLimit[SQLITE_LIMIT_LENGTH];
}
if( p1==0 ){
#ifdef SQLITE_SUBSTR_COMPATIBILITY
/* If SUBSTR_COMPATIBILITY is defined then substr(X,0,N) work the same as
** as substr(X,1,N) - it returns the first N characters of X. This
** is essentially a back-out of the bug-fix in check-in [5fc125d362df4b8]
** from 2009-02-02 for compatibility of applications that exploited the
** old buggy behavior. */
p1 = 1; /* <rdar://problem/6778339> */
#endif
if( sqlite3_value_type(argv[1])==SQLITE_NULL ) return;
}
if( p1<0 ){
p1 += len;
if( p1<0 ){