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Overview
| Comment: | Tweaks to the SUBSTR() function to make it dramatically faster in the common case where the input string is large but the 2nd and 3rd arguments are small positive integers. |
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| Downloads: | Tarball | ZIP archive | SQL archive |
| Timelines: | family | ancestors | descendants | both | trunk |
| Files: | files | file ages | folders |
| SHA1: |
5a474a867c5988ad5ec03719516fdd38 |
| User & Date: | drh 2009-11-11 20:53:31 |
Context
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2009-11-11
| ||
| 23:48 | Remove an obsolete (and incorrect) comment from sqlite3MemCompare(). No changes to code. check-in: c15b70b3 user: drh tags: trunk | |
| 20:53 | Tweaks to the SUBSTR() function to make it dramatically faster in the common case where the input string is large but the 2nd and 3rd arguments are small positive integers. check-in: 5a474a86 user: drh tags: trunk | |
| 13:17 | Allow media sector sizes as small as 32. The former minimum size was 512. check-in: 5a32bfc1 user: drh tags: trunk | |
Changes
Changes to src/func.c.
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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]);
if( p0type==SQLITE_BLOB ){
len = sqlite3_value_bytes(argv[0]);
z = sqlite3_value_blob(argv[0]);
if( z==0 ) return;
assert( len==sqlite3_value_bytes(argv[0]) );
}else{
z = sqlite3_value_text(argv[0]);
if( z==0 ) return;
len = 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 ){
p2 = -p2;
negP2 = 1;
}
}else{
................................................................................
p1 -= p2;
if( p1<0 ){
p2 += p1;
p1 = 0;
}
}
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);
p1--;
}
for(z2=z; *z2 && p2; p2--){
SQLITE_SKIP_UTF8(z2);
}
sqlite3_result_text(context, (char*)z, (int)(z2-z), SQLITE_TRANSIENT);
}else{
sqlite3_result_blob(context, (char*)&z[p1], (int)p2, SQLITE_TRANSIENT);
}
}
/*
** Implementation of the round() function
*/
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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_int(argv[1]);
if( p0type==SQLITE_BLOB ){
len = sqlite3_value_bytes(argv[0]);
z = sqlite3_value_blob(argv[0]);
if( z==0 ) return;
assert( len==sqlite3_value_bytes(argv[0]) );
}else{
z = sqlite3_value_text(argv[0]);
if( z==0 ) return;
len = 0;
if( p1<0 ){
for(z2=z; *z2; len++){
SQLITE_SKIP_UTF8(z2);
}
}
}
if( argc==3 ){
p2 = sqlite3_value_int(argv[2]);
if( p2<0 ){
p2 = -p2;
negP2 = 1;
}
}else{
................................................................................
p1 -= p2;
if( p1<0 ){
p2 += p1;
p1 = 0;
}
}
assert( p1>=0 && p2>=0 );
if( p0type!=SQLITE_BLOB ){
while( *z && p1 ){
SQLITE_SKIP_UTF8(z);
p1--;
}
for(z2=z; *z2 && p2; p2--){
SQLITE_SKIP_UTF8(z2);
}
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);
}
}
/*
** Implementation of the round() function
*/
|