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Overview
Comment: | Add documentation for fts5 synonym support. |
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Downloads: | Tarball | ZIP archive |
Timelines: | family | ancestors | descendants | both | fts5-incompatible |
Files: | files | file ages | folders |
SHA1: |
58aa1f435959852df74f1bca8e0bdbc4 |
User & Date: | dan 2015-09-03 18:05:09.505 |
Context
2015-09-03
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18:57 | Merge enhancements from trunk. (check-in: 4b49fe9969 user: dan tags: fts5-incompatible) | |
18:05 | Add documentation for fts5 synonym support. (check-in: 58aa1f4359 user: dan tags: fts5-incompatible) | |
15:37 | Add tests to improve coverage of fts5_varint.c. (check-in: 89f24f31a8 user: dan tags: fts5-incompatible) | |
Changes
Changes to ext/fts5/extract_api_docs.tcl.
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104 105 106 107 108 109 110 111 112 113 114 115 116 | set res "<dl>\n" foreach line [split [string trim $docs] "\n"] { regexp {[*][*](.*)} $line -> line if {[regexp {^ ?x.*:} $line]} { append res "<dt><b>$line</b></dt><dd><p style=margin-top:0>\n" continue } if {[string trim $line] == ""} { append res "<p>\n" } else { append res "$line\n" } } | > > > < | 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 | set res "<dl>\n" foreach line [split [string trim $docs] "\n"] { regexp {[*][*](.*)} $line -> line if {[regexp {^ ?x.*:} $line]} { append res "<dt><b>$line</b></dt><dd><p style=margin-top:0>\n" continue } if {[regexp {SYNONYM SUPPORT} $line]} { set line "</dl><h3>Synonym Support</h3>" } if {[string trim $line] == ""} { append res "<p>\n" } else { append res "$line\n" } } set res } proc get_api_docs {data} { # Initialize global array M as a map from Fts5StructureApi member name # to member definition. i.e. |
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204 205 206 207 208 209 210 211 212 213 214 215 216 217 | switch $::extract_api_docs_mode { fts5_api { output [get_fts5_struct $data "typedef struct fts5_api" "^\};"] } fts5_tokenizer { output [get_fts5_struct $data "typedef struct Fts5Tokenizer" "^\};"] } fts5_extension { output [get_fts5_struct $data "typedef.*Fts5ExtensionApi" "^.;"] } Fts5ExtensionApi { | > > > > | 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 | switch $::extract_api_docs_mode { fts5_api { output [get_fts5_struct $data "typedef struct fts5_api" "^\};"] } fts5_tokenizer { output [get_fts5_struct $data "typedef struct Fts5Tokenizer" "^\};"] output [get_fts5_struct $data \ "Flags that may be passed as the third argument to xTokenize()" \ "#define FTS5_TOKEN_COLOCATED" ] } fts5_extension { output [get_fts5_struct $data "typedef.*Fts5ExtensionApi" "^.;"] } Fts5ExtensionApi { |
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Changes to ext/fts5/fts5.h.
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274 275 276 277 278 279 280 | ** xDelete: ** This function is invoked to delete a tokenizer handle previously ** allocated using xCreate(). Fts5 guarantees that this function will ** be invoked exactly once for each successful call to xCreate(). ** ** xTokenize: ** This function is expected to tokenize the nText byte string indicated | | | | > > > > > > > > > > > > > > > > > > > > > > > > | | | | > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > | | 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 | ** xDelete: ** This function is invoked to delete a tokenizer handle previously ** allocated using xCreate(). Fts5 guarantees that this function will ** be invoked exactly once for each successful call to xCreate(). ** ** xTokenize: ** This function is expected to tokenize the nText byte string indicated ** by argument pText. pText may or may not be nul-terminated. The first ** argument passed to this function is a pointer to an Fts5Tokenizer object ** returned by an earlier call to xCreate(). ** ** The second argument indicates the reason that FTS5 is requesting ** tokenization of the supplied text. This is always one of the following ** four values: ** ** <ul><li> <b>FTS5_TOKENIZE_DOCUMENT</b> - A document is being inserted into ** or removed from the FTS table. The tokenizer is being invoked to ** determine the set of tokens to add to (or delete from) the ** FTS index. ** ** <li> <b>FTS5_TOKENIZE_QUERY</b> - A MATCH query is being executed ** against the FTS index. The tokenizer is being called to tokenize ** a bareword or quoted string specified as part of the query. ** ** <li> <b>(FTS5_TOKENIZE_QUERY | FTS5_TOKENIZE_PREFIX)</b> - Same as ** FTS5_TOKENIZE_QUERY, except that the bareword or quoted string is ** followed by a "*" character, indicating that the last token ** returned by the tokenizer will be treated as a token prefix. ** ** <li> <b>FTS5_TOKENIZE_AUX</b> - The tokenizer is being invoked to ** satisfy an fts5_api.xTokenize() request made by an auxiliary ** function. Or an fts5_api.xColumnSize() request made by the same ** on a columnsize=0 database. ** </ul> ** ** For each token in the input string, the supplied callback xToken() must ** be invoked. The first argument to it should be a copy of the pointer ** passed as the second argument to xTokenize(). The third and fourth ** arguments are a pointer to a buffer containing the token text, and the ** size of the token in bytes. The 4th and 5th arguments are the byte offsets ** of the first byte of and first byte immediately following the text from ** which the token is derived within the input. ** ** The second argument passed to the xToken() callback ("tflags") should ** normally be set to 0. The exception is if the tokenizer supports ** synonyms. In this case see the discussion below for details. ** ** FTS5 assumes the xToken() callback is invoked for each token in the ** order that they occur within the input text. ** ** If an xToken() callback returns any value other than SQLITE_OK, then ** the tokenization should be abandoned and the xTokenize() method should ** immediately return a copy of the xToken() return value. Or, if the ** input buffer is exhausted, xTokenize() should return SQLITE_OK. Finally, ** if an error occurs with the xTokenize() implementation itself, it ** may abandon the tokenization and return any error code other than ** SQLITE_OK or SQLITE_DONE. ** ** SYNONYM SUPPORT ** ** Custom tokenizers may also support synonyms. Consider a case in which a ** user wishes to query for a phrase such as "first place". Using the ** built-in tokenizers, the FTS5 query 'first + place' will match instances ** of "first place" within the document set, but not alternative forms ** such as "1st place". In some applications, it would be better to match ** all instances of "first place" or "1st place" regardless of which form ** the user specified in the MATCH query text. ** ** There are several ways to approach this in FTS5: ** ** <ol><li> By mapping all synonyms to a single token. In this case, the ** In the above example, this means that the tokenizer returns the ** same token for inputs "first" and "1st". Say that token is in ** fact "first", so that when the user inserts the document "I won ** 1st place" entries are added to the index for tokens "i", "won", ** "first" and "place". If the user then queries for '1st + place', ** the tokenizer substitutes "first" for "1st" and the query works ** as expected. ** ** <li> By adding multiple synonyms for a single term to the FTS index. ** In this case, when tokenizing query text, the tokenizer may ** provide multiple synonyms for a single term within the document. ** FTS5 then queries the index for each synonym individually. For ** example, faced with the query: ** ** <codeblock> ** ... MATCH 'first place'</codeblock> ** ** the tokenizer offers both "1st" and "first" as synonyms for the ** first token in the MATCH query and FTS5 effectively runs a query ** similar to: ** ** <codeblock> ** ... MATCH '(first OR 1st) place'</codeblock> ** ** except that, for the purposes of auxiliary functions, the query ** still appears to contain just two phrases - "(first OR 1st)" ** being treated as a single phrase. ** ** <li> By adding multiple synonyms for a single term to the FTS index. ** Using this method, when tokenizing document text, the tokenizer ** provides multiple synonyms for each token. So that when a ** document such as "I won first place" is tokenized, entries are ** added to the FTS index for "i", "won", "first", "1st" and ** "place". ** ** This way, even if the tokenizer does not provide synonyms ** when tokenizing query text (it should not - to do would be ** inefficient), it doesn't matter if the user queries for ** 'first + place' or '1st + place', as there are entires in the ** FTS index corresponding to both forms of the first token. ** </ol> ** ** Whether is is parsing document or query text, any call to xToken that ** specifies a <i>tflags</i> argument with the FTS5_TOKEN_COLOCATED bit ** is considered to supply a synonym for the previous token. For example, ** when parsing the document "I won first place", a tokenizer that supports ** synonyms would call xToken() 5 times, as follows: ** ** <codeblock> ** xToken(pCtx, 0, "i", 1, 0, 1); ** xToken(pCtx, 0, "won", 3, 2, 5); ** xToken(pCtx, 0, "first", 5, 6, 11); ** xToken(pCtx, FTS5_TOKEN_COLOCATED, "1st", 3, 6, 11); ** xToken(pCtx, 0, "place", 5, 12, 17); **</codeblock> ** ** It is an error to specify the FTS5_TOKEN_COLOCATED flag the first time ** xToken() is called. Multiple synonyms may be specified for a single token ** by making multiple calls to xToken(FTS5_TOKEN_COLOCATED) in sequence. ** There is no limit to the number of synonyms that may be provided for a ** single token. ** ** In many cases, method (1) above is the best approach. It does not add ** extra data to the FTS index or require FTS5 to query for multiple terms, ** so it is efficient in terms of disk space and query speed. However, it ** does not support prefix queries very well. If, as suggested above, the ** token "first" is subsituted for "1st" by the tokenizer, then the query: ** ** <codeblock> ** ... MATCH '1s*'</codeblock> ** ** will not match documents that contain the token "1st" (as the tokenizer ** will probably not map "1s" to any prefix of "first"). ** ** For full prefix support, method (3) may be preferred. In this case, ** because the index contains entries for both "first" and "1st", prefix ** queries such as 'fi*' or '1s*' will match correctly. However, because ** extra entries are added to the FTS index, this method uses more space ** within the database. ** ** Method (2) offers a midpoint between (1) and (3). Using this method, ** a query such as '1s*' will match documents that contain the literal ** token "1st", but not "first" (assuming the tokenizer is not able to ** provide synonyms for prefixes). However, a non-prefix query like '1st' ** will match against "1st" and "first". This method does not require ** extra disk space, as no extra entries are added to the FTS index. ** On the other hand, it may require more CPU cycles to run MATCH queries, ** as separate queries of the FTS index are required for each synonym. ** ** When using methods (2) or (3), it is important that the tokenizer only ** provide synonyms when tokenizing document text (method (2)) or query ** text (method (3)), not both. Doing so will not cause any errors, but is ** inefficient. */ typedef struct Fts5Tokenizer Fts5Tokenizer; typedef struct fts5_tokenizer fts5_tokenizer; struct fts5_tokenizer { int (*xCreate)(void*, const char **azArg, int nArg, Fts5Tokenizer **ppOut); void (*xDelete)(Fts5Tokenizer*); int (*xTokenize)(Fts5Tokenizer*, void *pCtx, int flags, /* Mask of FTS5_TOKENIZE_* flags */ const char *pText, int nText, int (*xToken)( void *pCtx, /* Copy of 2nd argument to xTokenize() */ int tflags, /* Mask of FTS5_TOKEN_* flags */ const char *pToken, /* Pointer to buffer containing token */ int nToken, /* Size of token in bytes */ int iStart, /* Byte offset of token within input text */ |
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