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Diffstat (limited to 'ext/fts5/fts5.h')
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diff --git a/ext/fts5/fts5.h b/ext/fts5/fts5.h new file mode 100644 index 0000000..081e534 --- /dev/null +++ b/ext/fts5/fts5.h @@ -0,0 +1,575 @@ +/* +** 2014 May 31 +** +** The author disclaims copyright to this source code. In place of +** a legal notice, here is a blessing: +** +** May you do good and not evil. +** May you find forgiveness for yourself and forgive others. +** May you share freely, never taking more than you give. +** +****************************************************************************** +** +** Interfaces to extend FTS5. Using the interfaces defined in this file, +** FTS5 may be extended with: +** +** * custom tokenizers, and +** * custom auxiliary functions. +*/ + + +#ifndef _FTS5_H +#define _FTS5_H + +#include "sqlite3.h" + +#ifdef __cplusplus +extern "C" { +#endif + +/************************************************************************* +** CUSTOM AUXILIARY FUNCTIONS +** +** Virtual table implementations may overload SQL functions by implementing +** the sqlite3_module.xFindFunction() method. +*/ + +typedef struct Fts5ExtensionApi Fts5ExtensionApi; +typedef struct Fts5Context Fts5Context; +typedef struct Fts5PhraseIter Fts5PhraseIter; + +typedef void (*fts5_extension_function)( + const Fts5ExtensionApi *pApi, /* API offered by current FTS version */ + Fts5Context *pFts, /* First arg to pass to pApi functions */ + sqlite3_context *pCtx, /* Context for returning result/error */ + int nVal, /* Number of values in apVal[] array */ + sqlite3_value **apVal /* Array of trailing arguments */ +); + +struct Fts5PhraseIter { + const unsigned char *a; + const unsigned char *b; +}; + +/* +** EXTENSION API FUNCTIONS +** +** xUserData(pFts): +** Return a copy of the context pointer the extension function was +** registered with. +** +** xColumnTotalSize(pFts, iCol, pnToken): +** If parameter iCol is less than zero, set output variable *pnToken +** to the total number of tokens in the FTS5 table. Or, if iCol is +** non-negative but less than the number of columns in the table, return +** the total number of tokens in column iCol, considering all rows in +** the FTS5 table. +** +** If parameter iCol is greater than or equal to the number of columns +** in the table, SQLITE_RANGE is returned. Or, if an error occurs (e.g. +** an OOM condition or IO error), an appropriate SQLite error code is +** returned. +** +** xColumnCount(pFts): +** Return the number of columns in the table. +** +** xColumnSize(pFts, iCol, pnToken): +** If parameter iCol is less than zero, set output variable *pnToken +** to the total number of tokens in the current row. Or, if iCol is +** non-negative but less than the number of columns in the table, set +** *pnToken to the number of tokens in column iCol of the current row. +** +** If parameter iCol is greater than or equal to the number of columns +** in the table, SQLITE_RANGE is returned. Or, if an error occurs (e.g. +** an OOM condition or IO error), an appropriate SQLite error code is +** returned. +** +** This function may be quite inefficient if used with an FTS5 table +** created with the "columnsize=0" option. +** +** xColumnText: +** This function attempts to retrieve the text of column iCol of the +** current document. If successful, (*pz) is set to point to a buffer +** containing the text in utf-8 encoding, (*pn) is set to the size in bytes +** (not characters) of the buffer and SQLITE_OK is returned. Otherwise, +** if an error occurs, an SQLite error code is returned and the final values +** of (*pz) and (*pn) are undefined. +** +** xPhraseCount: +** Returns the number of phrases in the current query expression. +** +** xPhraseSize: +** Returns the number of tokens in phrase iPhrase of the query. Phrases +** are numbered starting from zero. +** +** xInstCount: +** Set *pnInst to the total number of occurrences of all phrases within +** the query within the current row. Return SQLITE_OK if successful, or +** an error code (i.e. SQLITE_NOMEM) if an error occurs. +** +** This API can be quite slow if used with an FTS5 table created with the +** "detail=none" or "detail=column" option. If the FTS5 table is created +** with either "detail=none" or "detail=column" and "content=" option +** (i.e. if it is a contentless table), then this API always returns 0. +** +** xInst: +** Query for the details of phrase match iIdx within the current row. +** Phrase matches are numbered starting from zero, so the iIdx argument +** should be greater than or equal to zero and smaller than the value +** output by xInstCount(). +** +** Usually, output parameter *piPhrase is set to the phrase number, *piCol +** to the column in which it occurs and *piOff the token offset of the +** first token of the phrase. Returns SQLITE_OK if successful, or an error +** code (i.e. SQLITE_NOMEM) if an error occurs. +** +** This API can be quite slow if used with an FTS5 table created with the +** "detail=none" or "detail=column" option. +** +** xRowid: +** Returns the rowid of the current row. +** +** xTokenize: +** Tokenize text using the tokenizer belonging to the FTS5 table. +** +** xQueryPhrase(pFts5, iPhrase, pUserData, xCallback): +** This API function is used to query the FTS table for phrase iPhrase +** of the current query. Specifically, a query equivalent to: +** +** ... FROM ftstable WHERE ftstable MATCH $p ORDER BY rowid +** +** with $p set to a phrase equivalent to the phrase iPhrase of the +** current query is executed. Any column filter that applies to +** phrase iPhrase of the current query is included in $p. For each +** row visited, the callback function passed as the fourth argument +** is invoked. The context and API objects passed to the callback +** function may be used to access the properties of each matched row. +** Invoking Api.xUserData() returns a copy of the pointer passed as +** the third argument to pUserData. +** +** If the callback function returns any value other than SQLITE_OK, the +** query is abandoned and the xQueryPhrase function returns immediately. +** If the returned value is SQLITE_DONE, xQueryPhrase returns SQLITE_OK. +** Otherwise, the error code is propagated upwards. +** +** If the query runs to completion without incident, SQLITE_OK is returned. +** Or, if some error occurs before the query completes or is aborted by +** the callback, an SQLite error code is returned. +** +** +** xSetAuxdata(pFts5, pAux, xDelete) +** +** Save the pointer passed as the second argument as the extension function's +** "auxiliary data". The pointer may then be retrieved by the current or any +** future invocation of the same fts5 extension function made as part of +** the same MATCH query using the xGetAuxdata() API. +** +** Each extension function is allocated a single auxiliary data slot for +** each FTS query (MATCH expression). If the extension function is invoked +** more than once for a single FTS query, then all invocations share a +** single auxiliary data context. +** +** If there is already an auxiliary data pointer when this function is +** invoked, then it is replaced by the new pointer. If an xDelete callback +** was specified along with the original pointer, it is invoked at this +** point. +** +** The xDelete callback, if one is specified, is also invoked on the +** auxiliary data pointer after the FTS5 query has finished. +** +** If an error (e.g. an OOM condition) occurs within this function, +** the auxiliary data is set to NULL and an error code returned. If the +** xDelete parameter was not NULL, it is invoked on the auxiliary data +** pointer before returning. +** +** +** xGetAuxdata(pFts5, bClear) +** +** Returns the current auxiliary data pointer for the fts5 extension +** function. See the xSetAuxdata() method for details. +** +** If the bClear argument is non-zero, then the auxiliary data is cleared +** (set to NULL) before this function returns. In this case the xDelete, +** if any, is not invoked. +** +** +** xRowCount(pFts5, pnRow) +** +** This function is used to retrieve the total number of rows in the table. +** In other words, the same value that would be returned by: +** +** SELECT count(*) FROM ftstable; +** +** xPhraseFirst() +** This function is used, along with type Fts5PhraseIter and the xPhraseNext +** method, to iterate through all instances of a single query phrase within +** the current row. This is the same information as is accessible via the +** xInstCount/xInst APIs. While the xInstCount/xInst APIs are more convenient +** to use, this API may be faster under some circumstances. To iterate +** through instances of phrase iPhrase, use the following code: +** +** Fts5PhraseIter iter; +** int iCol, iOff; +** for(pApi->xPhraseFirst(pFts, iPhrase, &iter, &iCol, &iOff); +** iCol>=0; +** pApi->xPhraseNext(pFts, &iter, &iCol, &iOff) +** ){ +** // An instance of phrase iPhrase at offset iOff of column iCol +** } +** +** The Fts5PhraseIter structure is defined above. Applications should not +** modify this structure directly - it should only be used as shown above +** with the xPhraseFirst() and xPhraseNext() API methods (and by +** xPhraseFirstColumn() and xPhraseNextColumn() as illustrated below). +** +** This API can be quite slow if used with an FTS5 table created with the +** "detail=none" or "detail=column" option. If the FTS5 table is created +** with either "detail=none" or "detail=column" and "content=" option +** (i.e. if it is a contentless table), then this API always iterates +** through an empty set (all calls to xPhraseFirst() set iCol to -1). +** +** xPhraseNext() +** See xPhraseFirst above. +** +** xPhraseFirstColumn() +** This function and xPhraseNextColumn() are similar to the xPhraseFirst() +** and xPhraseNext() APIs described above. The difference is that instead +** of iterating through all instances of a phrase in the current row, these +** APIs are used to iterate through the set of columns in the current row +** that contain one or more instances of a specified phrase. For example: +** +** Fts5PhraseIter iter; +** int iCol; +** for(pApi->xPhraseFirstColumn(pFts, iPhrase, &iter, &iCol); +** iCol>=0; +** pApi->xPhraseNextColumn(pFts, &iter, &iCol) +** ){ +** // Column iCol contains at least one instance of phrase iPhrase +** } +** +** This API can be quite slow if used with an FTS5 table created with the +** "detail=none" option. If the FTS5 table is created with either +** "detail=none" "content=" option (i.e. if it is a contentless table), +** then this API always iterates through an empty set (all calls to +** xPhraseFirstColumn() set iCol to -1). +** +** The information accessed using this API and its companion +** xPhraseFirstColumn() may also be obtained using xPhraseFirst/xPhraseNext +** (or xInst/xInstCount). The chief advantage of this API is that it is +** significantly more efficient than those alternatives when used with +** "detail=column" tables. +** +** xPhraseNextColumn() +** See xPhraseFirstColumn above. +*/ +struct Fts5ExtensionApi { + int iVersion; /* Currently always set to 3 */ + + void *(*xUserData)(Fts5Context*); + + int (*xColumnCount)(Fts5Context*); + int (*xRowCount)(Fts5Context*, sqlite3_int64 *pnRow); + int (*xColumnTotalSize)(Fts5Context*, int iCol, sqlite3_int64 *pnToken); + + int (*xTokenize)(Fts5Context*, + const char *pText, int nText, /* Text to tokenize */ + void *pCtx, /* Context passed to xToken() */ + int (*xToken)(void*, int, const char*, int, int, int) /* Callback */ + ); + + int (*xPhraseCount)(Fts5Context*); + int (*xPhraseSize)(Fts5Context*, int iPhrase); + + int (*xInstCount)(Fts5Context*, int *pnInst); + int (*xInst)(Fts5Context*, int iIdx, int *piPhrase, int *piCol, int *piOff); + + sqlite3_int64 (*xRowid)(Fts5Context*); + int (*xColumnText)(Fts5Context*, int iCol, const char **pz, int *pn); + int (*xColumnSize)(Fts5Context*, int iCol, int *pnToken); + + int (*xQueryPhrase)(Fts5Context*, int iPhrase, void *pUserData, + int(*)(const Fts5ExtensionApi*,Fts5Context*,void*) + ); + int (*xSetAuxdata)(Fts5Context*, void *pAux, void(*xDelete)(void*)); + void *(*xGetAuxdata)(Fts5Context*, int bClear); + + int (*xPhraseFirst)(Fts5Context*, int iPhrase, Fts5PhraseIter*, int*, int*); + void (*xPhraseNext)(Fts5Context*, Fts5PhraseIter*, int *piCol, int *piOff); + + int (*xPhraseFirstColumn)(Fts5Context*, int iPhrase, Fts5PhraseIter*, int*); + void (*xPhraseNextColumn)(Fts5Context*, Fts5PhraseIter*, int *piCol); +}; + +/* +** CUSTOM AUXILIARY FUNCTIONS +*************************************************************************/ + +/************************************************************************* +** CUSTOM TOKENIZERS +** +** Applications may also register custom tokenizer types. A tokenizer +** is registered by providing fts5 with a populated instance of the +** following structure. All structure methods must be defined, setting +** any member of the fts5_tokenizer struct to NULL leads to undefined +** behaviour. The structure methods are expected to function as follows: +** +** xCreate: +** This function is used to allocate and initialize a tokenizer instance. +** A tokenizer instance is required to actually tokenize text. +** +** The first argument passed to this function is a copy of the (void*) +** pointer provided by the application when the fts5_tokenizer object +** was registered with FTS5 (the third argument to xCreateTokenizer()). +** The second and third arguments are an array of nul-terminated strings +** containing the tokenizer arguments, if any, specified following the +** tokenizer name as part of the CREATE VIRTUAL TABLE statement used +** to create the FTS5 table. +** +** The final argument is an output variable. If successful, (*ppOut) +** should be set to point to the new tokenizer handle and SQLITE_OK +** returned. If an error occurs, some value other than SQLITE_OK should +** be returned. In this case, fts5 assumes that the final value of *ppOut +** is undefined. +** +** 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, using +** 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 querying the index for all synonyms of each query term +** separately. 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 so would be +** inefficient), it doesn't matter if the user queries for +** 'first + place' or '1st + place', as there are entries in the +** FTS index corresponding to both forms of the first token. +** </ol> +** +** Whether it 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 substituted 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 */ + int iEnd /* Byte offset of end of token within input text */ + ) + ); +}; + +/* Flags that may be passed as the third argument to xTokenize() */ +#define FTS5_TOKENIZE_QUERY 0x0001 +#define FTS5_TOKENIZE_PREFIX 0x0002 +#define FTS5_TOKENIZE_DOCUMENT 0x0004 +#define FTS5_TOKENIZE_AUX 0x0008 + +/* Flags that may be passed by the tokenizer implementation back to FTS5 +** as the third argument to the supplied xToken callback. */ +#define FTS5_TOKEN_COLOCATED 0x0001 /* Same position as prev. token */ + +/* +** END OF CUSTOM TOKENIZERS +*************************************************************************/ + +/************************************************************************* +** FTS5 EXTENSION REGISTRATION API +*/ +typedef struct fts5_api fts5_api; +struct fts5_api { + int iVersion; /* Currently always set to 2 */ + + /* Create a new tokenizer */ + int (*xCreateTokenizer)( + fts5_api *pApi, + const char *zName, + void *pContext, + fts5_tokenizer *pTokenizer, + void (*xDestroy)(void*) + ); + + /* Find an existing tokenizer */ + int (*xFindTokenizer)( + fts5_api *pApi, + const char *zName, + void **ppContext, + fts5_tokenizer *pTokenizer + ); + + /* Create a new auxiliary function */ + int (*xCreateFunction)( + fts5_api *pApi, + const char *zName, + void *pContext, + fts5_extension_function xFunction, + void (*xDestroy)(void*) + ); +}; + +/* +** END OF REGISTRATION API +*************************************************************************/ + +#ifdef __cplusplus +} /* end of the 'extern "C"' block */ +#endif + +#endif /* _FTS5_H */ |