SQLite

Check-in [ce51f1a2b6]
Login

Many hyperlinks are disabled.
Use anonymous login to enable hyperlinks.

Overview
Comment:Performance improvement on the instr() function, especially for large haystacks.
Downloads: Tarball | ZIP archive
Timelines: family | ancestors | descendants | both | trunk
Files: files | file ages | folders
SHA3-256: ce51f1a2b6a1789a5876e01cf829e45d84f3851d135a2fa5c44a56f948673a60
User & Date: drh 2019-01-08 15:18:24.588
Context
2019-01-08
20:02
Use 64-bit math to compute the sizes of memory allocations in extensions. (check-in: ca67f2ec0e user: drh tags: trunk)
15:18
Performance improvement on the instr() function, especially for large haystacks. (check-in: ce51f1a2b6 user: drh tags: trunk)
14:28
Fix a possible memory leak when trying to UPDATE a corrupt RTREE index. (check-in: 63eb803dbc user: drh tags: trunk)
Changes
Unified Diff Ignore Whitespace Patch
Changes to src/func.c.
︙︙
197
198
199
200
201
202
203

204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221

222


223
224
225
226
227
228
229

  const unsigned char *zHaystack;
  const unsigned char *zNeedle;
  int nHaystack;
  int nNeedle;
  int typeHaystack, typeNeedle;
  int N = 1;
  int isText;


  UNUSED_PARAMETER(argc);
  typeHaystack = sqlite3_value_type(argv[0]);
  typeNeedle = sqlite3_value_type(argv[1]);
  if( typeHaystack==SQLITE_NULL || typeNeedle==SQLITE_NULL ) return;
  nHaystack = sqlite3_value_bytes(argv[0]);
  nNeedle = sqlite3_value_bytes(argv[1]);
  if( nNeedle>0 ){
    if( typeHaystack==SQLITE_BLOB && typeNeedle==SQLITE_BLOB ){
      zHaystack = sqlite3_value_blob(argv[0]);
      zNeedle = sqlite3_value_blob(argv[1]);
      isText = 0;
    }else{
      zHaystack = sqlite3_value_text(argv[0]);
      zNeedle = sqlite3_value_text(argv[1]);
      isText = 1;
    }
    if( zNeedle==0 || (nHaystack && zHaystack==0) ) return;

    while( nNeedle<=nHaystack && memcmp(zHaystack, zNeedle, nNeedle)!=0 ){


      N++;
      do{
        nHaystack--;
        zHaystack++;
      }while( isText && (zHaystack[0]&0xc0)==0x80 );
    }
    if( nNeedle>nHaystack ) N = 0;








>


















>
|
>
>








197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233

  const unsigned char *zHaystack;
  const unsigned char *zNeedle;
  int nHaystack;
  int nNeedle;
  int typeHaystack, typeNeedle;
  int N = 1;
  int isText;
  unsigned char firstChar;

  UNUSED_PARAMETER(argc);
  typeHaystack = sqlite3_value_type(argv[0]);
  typeNeedle = sqlite3_value_type(argv[1]);
  if( typeHaystack==SQLITE_NULL || typeNeedle==SQLITE_NULL ) return;
  nHaystack = sqlite3_value_bytes(argv[0]);
  nNeedle = sqlite3_value_bytes(argv[1]);
  if( nNeedle>0 ){
    if( typeHaystack==SQLITE_BLOB && typeNeedle==SQLITE_BLOB ){
      zHaystack = sqlite3_value_blob(argv[0]);
      zNeedle = sqlite3_value_blob(argv[1]);
      isText = 0;
    }else{
      zHaystack = sqlite3_value_text(argv[0]);
      zNeedle = sqlite3_value_text(argv[1]);
      isText = 1;
    }
    if( zNeedle==0 || (nHaystack && zHaystack==0) ) return;
    firstChar = zNeedle[0];
    while( nNeedle<=nHaystack
       && (zHaystack[0]!=firstChar || memcmp(zHaystack, zNeedle, nNeedle)!=0)
    ){
      N++;
      do{
        nHaystack--;
        zHaystack++;
      }while( isText && (zHaystack[0]&0xc0)==0x80 );
    }
    if( nNeedle>nHaystack ) N = 0;
︙︙