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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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18
manifest
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@ -1,8 +1,8 @@
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Hash: SHA1
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D 2009-11-11T13:17:08
C Tweaks\sto\sthe\sSUBSTR()\sfunction\sto\smake\sit\sdramatically\sfaster\sin\sthe\scommon\ncase\swhere\sthe\sinput\sstring\sis\slarge\sbut\sthe\s2nd\sand\s3rd\sarguments\sare\ssmall\npositive\sintegers.
D 2009-11-11T20:53:31
F Makefile.arm-wince-mingw32ce-gcc fcd5e9cd67fe88836360bb4f9ef4cb7f8e2fb5a0
F Makefile.in 53f3dfa49f28ab5b80cb083fb7c9051e596bcfa1
F Makefile.linux-gcc d53183f4aa6a9192d249731c90dbdffbd2c68654
@ -120,7 +120,7 @@ F src/delete.c ec04635d152debdab70d4b30c5516b59282075ea
F src/expr.c be605c60ff84699f3087209f2f86a140a6a5e96c
F src/fault.c 160a0c015b6c2629d3899ed2daf63d75754a32bb
F src/fkey.c 41219cba186bcf0a053e42327dfa23aaba4f834a
F src/func.c 5949e2633bb8ff57cc70c1904db171ba23f13537
F src/func.c 97cb15ef7a7c32293a938589c9eb6933f6688a21
F src/global.c 271952d199a8cc59d4ce840b3bbbfd2f30c8ba32
F src/hash.c 458488dcc159c301b8e7686280ab209f1fb915af
F src/hash.h 2894c932d84d9f892d4b4023a75e501f83050970
@ -770,14 +770,14 @@ F tool/speedtest2.tcl ee2149167303ba8e95af97873c575c3e0fab58ff
F tool/speedtest8.c 2902c46588c40b55661e471d7a86e4dd71a18224
F tool/speedtest8inst1.c 293327bc76823f473684d589a8160bde1f52c14e
F tool/vdbe-compress.tcl d70ea6d8a19e3571d7ab8c9b75cba86d1173ff0f
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2
manifest.uuid
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@ -1 +1 @@
5a32bfc17ed022c85d2615c34b41a3dcae2594bd
5a474a867c5988ad5ec03719516fdd38f0da5c2c

16
src/func.c
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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);
}
}