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Tweaks to the SUBSTR() function to make it dramatically faster in the common

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case where the input string is large but the 2nd and 3rd arguments are small
positive integers.

FossilOrigin-Name: 5a474a867c5988ad5ec03719516fdd38f0da5c2c
This commit is contained in:
drh
2009-11-11 20:53:31 +00:00
parent 3c99d68b5c
commit 4adc4cb93b
3 changed files with 19 additions and 17 deletions
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src/func.c
+9 -7
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@@ -177,6 +177,7 @@ static void substrFunc(
return;
}
p0type = sqlite3_value_type(argv[0]);
p1 = sqlite3_value_int(argv[1]);
if( p0type==SQLITE_BLOB ){
len = sqlite3_value_bytes(argv[0]);
z = sqlite3_value_blob(argv[0]);
@@ -186,11 +187,12 @@ static void substrFunc(
z = sqlite3_value_text(argv[0]);
if( z==0 ) return;
len = 0;
for(z2=z; *z2; len++){
SQLITE_SKIP_UTF8(z2);
if( p1<0 ){
for(z2=z; *z2; len++){
SQLITE_SKIP_UTF8(z2);
}
}
}
p1 = sqlite3_value_int(argv[1]);
if( argc==3 ){
p2 = sqlite3_value_int(argv[2]);
if( p2<0 ){
@@ -220,10 +222,6 @@ static void substrFunc(
}
}
assert( p1>=0 && p2>=0 );
if( p1+p2>len ){
p2 = len-p1;
if( p2<0 ) p2 = 0;
}
if( p0type!=SQLITE_BLOB ){
while( *z && p1 ){
SQLITE_SKIP_UTF8(z);
@@ -234,6 +232,10 @@ static void substrFunc(
}
sqlite3_result_text(context, (char*)z, (int)(z2-z), SQLITE_TRANSIENT);
}else{
if( p1+p2>len ){
p2 = len-p1;
if( p2<0 ) p2 = 0;
}
sqlite3_result_blob(context, (char*)&z[p1], (int)p2, SQLITE_TRANSIENT);
}
}