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Overview
Comment: | Tighter compression of the keyword hash table. (CVS 3920) |
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Downloads: | Tarball | ZIP archive |
Timelines: | family | ancestors | descendants | both | trunk |
Files: | files | file ages | folders |
SHA1: |
681216767d7fabfccb0b12f6a81b18b6 |
User & Date: | drh 2007-05-04 17:07:53.000 |
Context
2007-05-04
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18:30 | Change incremental vacuum to be triggered by a pragma rather than a command. We have a lot to learn about this yet and we do not want to paint ourselves into a corner by commiting to specific syntax too early. (CVS 3921) (check-in: b13e497a32 user: drh tags: trunk) | |
17:07 | Tighter compression of the keyword hash table. (CVS 3920) (check-in: 681216767d user: drh tags: trunk) | |
16:14 | Optional parameter in the INCREMENTAL VACUUM statement specifies how many pages to vacuum from the database. (CVS 3919) (check-in: ed713f9ccb user: drh tags: trunk) | |
Changes
Changes to tool/mkkeywordhash.c.
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11 12 13 14 15 16 17 | ** A header comment placed at the beginning of generated code. */ static const char zHdr[] = "/***** This file contains automatically generated code ******\n" "**\n" "** The code in this file has been automatically generated by\n" "**\n" | | | 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 | ** A header comment placed at the beginning of generated code. */ static const char zHdr[] = "/***** This file contains automatically generated code ******\n" "**\n" "** The code in this file has been automatically generated by\n" "**\n" "** $Header: /home/drh/sqlite/trans/cvs/sqlite/sqlite/tool/mkkeywordhash.c,v 1.29 2007/05/04 17:07:53 drh Exp $\n" "**\n" "** The code in this file implements a function that determines whether\n" "** or not a given identifier is really an SQL keyword. The same thing\n" "** might be implemented more directly using a hand-written hash table.\n" "** But by using this automatically generated code, the size of the code\n" "** is substantially reduced. This is important for embedded applications\n" "** on platforms with limited memory.\n" |
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36 37 38 39 40 41 42 43 44 45 46 47 48 49 | char *zTokenType; /* Token value for this keyword */ int mask; /* Code this keyword if non-zero */ int id; /* Unique ID for this record */ int hash; /* Hash on the keyword */ int offset; /* Offset to start of name string */ int len; /* Length of this keyword, not counting final \000 */ int prefix; /* Number of characters in prefix */ int iNext; /* Index in aKeywordTable[] of next with same hash */ int substrId; /* Id to another keyword this keyword is embedded in */ int substrOffset; /* Offset into substrId for start of this keyword */ }; /* ** Define masks used to determine which keywords are allowed | > | 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 | char *zTokenType; /* Token value for this keyword */ int mask; /* Code this keyword if non-zero */ int id; /* Unique ID for this record */ int hash; /* Hash on the keyword */ int offset; /* Offset to start of name string */ int len; /* Length of this keyword, not counting final \000 */ int prefix; /* Number of characters in prefix */ int longestSuffix; /* Longest suffix that is a prefix on another word */ int iNext; /* Index in aKeywordTable[] of next with same hash */ int substrId; /* Id to another keyword this keyword is embedded in */ int substrOffset; /* Offset into substrId for start of this keyword */ }; /* ** Define masks used to determine which keywords are allowed |
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256 257 258 259 260 261 262 | { "VIEW", "TK_VIEW", VIEW }, { "VIRTUAL", "TK_VIRTUAL", VTAB }, { "WHEN", "TK_WHEN", ALWAYS }, { "WHERE", "TK_WHERE", ALWAYS }, }; /* Number of keywords */ | | | 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 | { "VIEW", "TK_VIEW", VIEW }, { "VIRTUAL", "TK_VIRTUAL", VTAB }, { "WHEN", "TK_WHEN", ALWAYS }, { "WHERE", "TK_WHERE", ALWAYS }, }; /* Number of keywords */ static int nKeyword = (sizeof(aKeywordTable)/sizeof(aKeywordTable[0])); /* An array to map all upper-case characters into their corresponding ** lower-case character. */ const unsigned char sqlite3UpperToLower[] = { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, |
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295 296 297 298 299 300 301 | n = strcmp(pA->zName, pB->zName); } return n; } static int keywordCompare2(const void *a, const void *b){ const Keyword *pA = (Keyword*)a; const Keyword *pB = (Keyword*)b; | > > | > | > | | | | > | | | > > > > > > > > > > > > > > > > > | | | | | | | | | | | > > | | 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 | n = strcmp(pA->zName, pB->zName); } return n; } static int keywordCompare2(const void *a, const void *b){ const Keyword *pA = (Keyword*)a; const Keyword *pB = (Keyword*)b; int n = pB->longestSuffix - pA->longestSuffix; if( n==0 ){ n = strcmp(pA->zName, pB->zName); } return n; } static int keywordCompare3(const void *a, const void *b){ const Keyword *pA = (Keyword*)a; const Keyword *pB = (Keyword*)b; int n = pA->offset - pB->offset; return n; } /* ** Return a KeywordTable entry with the given id */ static Keyword *findById(int id){ int i; for(i=0; i<nKeyword; i++){ if( aKeywordTable[i].id==id ) break; } return &aKeywordTable[i]; } /* ** This routine does the work. The generated code is printed on standard ** output. */ int main(int argc, char **argv){ int i, j, k, h; int bestSize, bestCount; int count; int nChar; int totalLen = 0; int aHash[1000]; /* 1000 is much bigger than nKeyword */ /* Remove entries from the list of keywords that have mask==0 */ for(i=j=0; i<nKeyword; i++){ if( aKeywordTable[i].mask==0 ) continue; if( j<i ){ aKeywordTable[j] = aKeywordTable[i]; } j++; } nKeyword = j; /* Fill in the lengths of strings and hashes for all entries. */ for(i=0; i<nKeyword; i++){ Keyword *p = &aKeywordTable[i]; p->len = strlen(p->zName); totalLen += p->len; p->hash = (UpperToLower[p->zName[0]]*4) ^ (UpperToLower[p->zName[p->len-1]]*3) ^ p->len; p->id = i+1; } /* Sort the table from shortest to longest keyword */ qsort(aKeywordTable, nKeyword, sizeof(aKeywordTable[0]), keywordCompare1); /* Look for short keywords embedded in longer keywords */ for(i=nKeyword-2; i>=0; i--){ Keyword *p = &aKeywordTable[i]; for(j=nKeyword-1; j>i && p->substrId==0; j--){ Keyword *pOther = &aKeywordTable[j]; if( pOther->substrId ) continue; if( pOther->len<=p->len ) continue; for(k=0; k<=pOther->len-p->len; k++){ if( memcmp(p->zName, &pOther->zName[k], p->len)==0 ){ p->substrId = pOther->id; p->substrOffset = k; break; } } } } /* Compute the longestSuffix value for every word */ for(i=0; i<nKeyword; i++){ Keyword *p = &aKeywordTable[i]; if( p->substrId ) continue; for(j=0; j<nKeyword; j++){ Keyword *pOther; if( j==i ) continue; pOther = &aKeywordTable[j]; if( pOther->substrId ) continue; for(k=p->longestSuffix+1; k<p->len && k<pOther->len; k++){ if( memcmp(&p->zName[p->len-k], pOther->zName, k)==0 ){ p->longestSuffix = k; } } } } /* Sort the table into reverse order by length */ qsort(aKeywordTable, nKeyword, sizeof(aKeywordTable[0]), keywordCompare2); /* Fill in the offset for all entries */ nChar = 0; for(i=0; i<nKeyword; i++){ Keyword *p = &aKeywordTable[i]; if( p->offset>0 || p->substrId ) continue; p->offset = nChar; nChar += p->len; for(k=p->len-1; k>=1; k--){ for(j=i+1; j<nKeyword; j++){ Keyword *pOther = &aKeywordTable[j]; if( pOther->offset>0 || pOther->substrId ) continue; if( pOther->len<=k ) continue; if( memcmp(&p->zName[p->len-k], pOther->zName, k)==0 ){ p = pOther; p->offset = nChar - k; nChar = p->offset + p->len; p->zName += k; p->len -= k; p->prefix = k; j = i; k = p->len; } } } } for(i=0; i<nKeyword; i++){ Keyword *p = &aKeywordTable[i]; if( p->substrId ){ p->offset = findById(p->substrId)->offset + p->substrOffset; } } /* Sort the table by offset */ qsort(aKeywordTable, nKeyword, sizeof(aKeywordTable[0]), keywordCompare3); /* Figure out how big to make the hash table in order to minimize the ** number of collisions */ bestSize = nKeyword; bestCount = nKeyword*nKeyword; for(i=nKeyword/2; i<=2*nKeyword; i++){ for(j=0; j<i; j++) aHash[j] = 0; for(j=0; j<nKeyword; j++){ h = aKeywordTable[j].hash % i; aHash[h] *= 2; aHash[h]++; } for(j=count=0; j<i; j++) count += aHash[j]; if( count<bestCount ){ bestCount = count; bestSize = i; } } /* Compute the hash */ for(i=0; i<bestSize; i++) aHash[i] = 0; for(i=0; i<nKeyword; i++){ h = aKeywordTable[i].hash % bestSize; aKeywordTable[i].iNext = aHash[h]; aHash[h] = i+1; } /* Begin generating code */ printf("%s", zHdr); printf("/* Hash score: %d */\n", bestCount); printf("static int keywordCode(const char *z, int n){\n"); printf(" /* zText[] encodes %d bytes of keywords in %d bytes */\n", totalLen + nKeyword, nChar+1 ); printf(" static const char zText[%d] =\n", nChar+1); for(i=j=0; i<nKeyword; i++){ Keyword *p = &aKeywordTable[i]; if( p->substrId ) continue; if( j==0 ) printf(" \""); printf("%s", p->zName); j += p->len; if( j>60 ){ printf("\"\n"); |
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461 462 463 464 465 466 467 | if( j>12 ){ printf("\n"); j = 0; } } printf("%s };\n", j==0 ? "" : "\n"); | | | | | | | | | | 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 | if( j>12 ){ printf("\n"); j = 0; } } printf("%s };\n", j==0 ? "" : "\n"); printf(" static const unsigned char aNext[%d] = {\n", nKeyword); for(i=j=0; i<nKeyword; i++){ if( j==0 ) printf(" "); printf(" %3d,", aKeywordTable[i].iNext); j++; if( j>12 ){ printf("\n"); j = 0; } } printf("%s };\n", j==0 ? "" : "\n"); printf(" static const unsigned char aLen[%d] = {\n", nKeyword); for(i=j=0; i<nKeyword; i++){ if( j==0 ) printf(" "); printf(" %3d,", aKeywordTable[i].len+aKeywordTable[i].prefix); j++; if( j>12 ){ printf("\n"); j = 0; } } printf("%s };\n", j==0 ? "" : "\n"); printf(" static const unsigned short int aOffset[%d] = {\n", nKeyword); for(i=j=0; i<nKeyword; i++){ if( j==0 ) printf(" "); printf(" %3d,", aKeywordTable[i].offset); j++; if( j>12 ){ printf("\n"); j = 0; } } printf("%s };\n", j==0 ? "" : "\n"); printf(" static const unsigned char aCode[%d] = {\n", nKeyword); for(i=j=0; i<nKeyword; i++){ char *zToken = aKeywordTable[i].zTokenType; if( j==0 ) printf(" "); printf("%s,%*s", zToken, (int)(14-strlen(zToken)), ""); j++; if( j>=5 ){ printf("\n"); j = 0; |
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