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fe15ed4342
(1) Extra paranoid defense against integer overflow. (2) Remove a stray blank line in an FTS5 comment. FossilOrigin-Name: 8563728deeb1d3ead9ff99a3ad2c7819b2223ead44e7374ecc7bbeda2d955ade
740 lines
32 KiB
C
740 lines
32 KiB
C
/*
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** 2014 May 31
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**
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** The author disclaims copyright to this source code. In place of
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** a legal notice, here is a blessing:
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**
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** May you do good and not evil.
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** May you find forgiveness for yourself and forgive others.
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** May you share freely, never taking more than you give.
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**
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******************************************************************************
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**
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** Interfaces to extend FTS5. Using the interfaces defined in this file,
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** FTS5 may be extended with:
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**
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** * custom tokenizers, and
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** * custom auxiliary functions.
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*/
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#ifndef _FTS5_H
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#define _FTS5_H
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#include "sqlite3.h"
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#ifdef __cplusplus
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extern "C" {
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#endif
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/*************************************************************************
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** CUSTOM AUXILIARY FUNCTIONS
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**
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** Virtual table implementations may overload SQL functions by implementing
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** the sqlite3_module.xFindFunction() method.
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*/
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typedef struct Fts5ExtensionApi Fts5ExtensionApi;
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typedef struct Fts5Context Fts5Context;
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typedef struct Fts5PhraseIter Fts5PhraseIter;
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typedef void (*fts5_extension_function)(
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const Fts5ExtensionApi *pApi, /* API offered by current FTS version */
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Fts5Context *pFts, /* First arg to pass to pApi functions */
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sqlite3_context *pCtx, /* Context for returning result/error */
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int nVal, /* Number of values in apVal[] array */
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sqlite3_value **apVal /* Array of trailing arguments */
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);
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struct Fts5PhraseIter {
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const unsigned char *a;
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const unsigned char *b;
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};
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/*
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** EXTENSION API FUNCTIONS
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**
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** xUserData(pFts):
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** Return a copy of the pUserData pointer passed to the xCreateFunction()
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** API when the extension function was registered.
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**
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** xColumnTotalSize(pFts, iCol, pnToken):
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** If parameter iCol is less than zero, set output variable *pnToken
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** to the total number of tokens in the FTS5 table. Or, if iCol is
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** non-negative but less than the number of columns in the table, return
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** the total number of tokens in column iCol, considering all rows in
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** the FTS5 table.
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**
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** If parameter iCol is greater than or equal to the number of columns
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** in the table, SQLITE_RANGE is returned. Or, if an error occurs (e.g.
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** an OOM condition or IO error), an appropriate SQLite error code is
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** returned.
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**
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** xColumnCount(pFts):
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** Return the number of columns in the table.
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**
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** xColumnSize(pFts, iCol, pnToken):
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** If parameter iCol is less than zero, set output variable *pnToken
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** to the total number of tokens in the current row. Or, if iCol is
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** non-negative but less than the number of columns in the table, set
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** *pnToken to the number of tokens in column iCol of the current row.
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**
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** If parameter iCol is greater than or equal to the number of columns
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** in the table, SQLITE_RANGE is returned. Or, if an error occurs (e.g.
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** an OOM condition or IO error), an appropriate SQLite error code is
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** returned.
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**
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** This function may be quite inefficient if used with an FTS5 table
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** created with the "columnsize=0" option.
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**
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** xColumnText:
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** If parameter iCol is less than zero, or greater than or equal to the
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** number of columns in the table, SQLITE_RANGE is returned.
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**
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** Otherwise, this function attempts to retrieve the text of column iCol of
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** the current document. If successful, (*pz) is set to point to a buffer
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** containing the text in utf-8 encoding, (*pn) is set to the size in bytes
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** (not characters) of the buffer and SQLITE_OK is returned. Otherwise,
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** if an error occurs, an SQLite error code is returned and the final values
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** of (*pz) and (*pn) are undefined.
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**
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** xPhraseCount:
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** Returns the number of phrases in the current query expression.
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**
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** xPhraseSize:
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** If parameter iCol is less than zero, or greater than or equal to the
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** number of phrases in the current query, as returned by xPhraseCount,
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** 0 is returned. Otherwise, this function returns the number of tokens in
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** phrase iPhrase of the query. Phrases are numbered starting from zero.
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**
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** xInstCount:
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** Set *pnInst to the total number of occurrences of all phrases within
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** the query within the current row. Return SQLITE_OK if successful, or
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** an error code (i.e. SQLITE_NOMEM) if an error occurs.
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**
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** This API can be quite slow if used with an FTS5 table created with the
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** "detail=none" or "detail=column" option. If the FTS5 table is created
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** with either "detail=none" or "detail=column" and "content=" option
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** (i.e. if it is a contentless table), then this API always returns 0.
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**
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** xInst:
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** Query for the details of phrase match iIdx within the current row.
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** Phrase matches are numbered starting from zero, so the iIdx argument
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** should be greater than or equal to zero and smaller than the value
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** output by xInstCount(). If iIdx is less than zero or greater than
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** or equal to the value returned by xInstCount(), SQLITE_RANGE is returned.
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**
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** Otherwise, output parameter *piPhrase is set to the phrase number, *piCol
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** to the column in which it occurs and *piOff the token offset of the
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** first token of the phrase. SQLITE_OK is returned if successful, or an
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** error code (i.e. SQLITE_NOMEM) if an error occurs.
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**
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** This API can be quite slow if used with an FTS5 table created with the
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** "detail=none" or "detail=column" option.
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**
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** xRowid:
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** Returns the rowid of the current row.
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**
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** xTokenize:
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** Tokenize text using the tokenizer belonging to the FTS5 table.
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**
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** xQueryPhrase(pFts5, iPhrase, pUserData, xCallback):
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** This API function is used to query the FTS table for phrase iPhrase
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** of the current query. Specifically, a query equivalent to:
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**
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** ... FROM ftstable WHERE ftstable MATCH $p ORDER BY rowid
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**
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** with $p set to a phrase equivalent to the phrase iPhrase of the
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** current query is executed. Any column filter that applies to
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** phrase iPhrase of the current query is included in $p. For each
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** row visited, the callback function passed as the fourth argument
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** is invoked. The context and API objects passed to the callback
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** function may be used to access the properties of each matched row.
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** Invoking Api.xUserData() returns a copy of the pointer passed as
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** the third argument to pUserData.
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**
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** If parameter iPhrase is less than zero, or greater than or equal to
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** the number of phrases in the query, as returned by xPhraseCount(),
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** this function returns SQLITE_RANGE.
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**
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** If the callback function returns any value other than SQLITE_OK, the
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** query is abandoned and the xQueryPhrase function returns immediately.
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** If the returned value is SQLITE_DONE, xQueryPhrase returns SQLITE_OK.
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** Otherwise, the error code is propagated upwards.
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**
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** If the query runs to completion without incident, SQLITE_OK is returned.
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** Or, if some error occurs before the query completes or is aborted by
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** the callback, an SQLite error code is returned.
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**
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**
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** xSetAuxdata(pFts5, pAux, xDelete)
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**
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** Save the pointer passed as the second argument as the extension function's
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** "auxiliary data". The pointer may then be retrieved by the current or any
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** future invocation of the same fts5 extension function made as part of
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** the same MATCH query using the xGetAuxdata() API.
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**
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** Each extension function is allocated a single auxiliary data slot for
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** each FTS query (MATCH expression). If the extension function is invoked
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** more than once for a single FTS query, then all invocations share a
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** single auxiliary data context.
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**
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** If there is already an auxiliary data pointer when this function is
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** invoked, then it is replaced by the new pointer. If an xDelete callback
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** was specified along with the original pointer, it is invoked at this
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** point.
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**
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** The xDelete callback, if one is specified, is also invoked on the
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** auxiliary data pointer after the FTS5 query has finished.
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**
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** If an error (e.g. an OOM condition) occurs within this function,
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** the auxiliary data is set to NULL and an error code returned. If the
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** xDelete parameter was not NULL, it is invoked on the auxiliary data
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** pointer before returning.
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**
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**
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** xGetAuxdata(pFts5, bClear)
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**
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** Returns the current auxiliary data pointer for the fts5 extension
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** function. See the xSetAuxdata() method for details.
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**
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** If the bClear argument is non-zero, then the auxiliary data is cleared
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** (set to NULL) before this function returns. In this case the xDelete,
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** if any, is not invoked.
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**
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**
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** xRowCount(pFts5, pnRow)
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**
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** This function is used to retrieve the total number of rows in the table.
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** In other words, the same value that would be returned by:
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**
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** SELECT count(*) FROM ftstable;
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**
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** xPhraseFirst()
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** This function is used, along with type Fts5PhraseIter and the xPhraseNext
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** method, to iterate through all instances of a single query phrase within
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** the current row. This is the same information as is accessible via the
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** xInstCount/xInst APIs. While the xInstCount/xInst APIs are more convenient
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** to use, this API may be faster under some circumstances. To iterate
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** through instances of phrase iPhrase, use the following code:
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**
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** Fts5PhraseIter iter;
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** int iCol, iOff;
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** for(pApi->xPhraseFirst(pFts, iPhrase, &iter, &iCol, &iOff);
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** iCol>=0;
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** pApi->xPhraseNext(pFts, &iter, &iCol, &iOff)
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** ){
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** // An instance of phrase iPhrase at offset iOff of column iCol
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** }
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**
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** The Fts5PhraseIter structure is defined above. Applications should not
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** modify this structure directly - it should only be used as shown above
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** with the xPhraseFirst() and xPhraseNext() API methods (and by
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** xPhraseFirstColumn() and xPhraseNextColumn() as illustrated below).
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**
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** This API can be quite slow if used with an FTS5 table created with the
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** "detail=none" or "detail=column" option. If the FTS5 table is created
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** with either "detail=none" or "detail=column" and "content=" option
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** (i.e. if it is a contentless table), then this API always iterates
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** through an empty set (all calls to xPhraseFirst() set iCol to -1).
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**
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** In all cases, matches are visited in (column ASC, offset ASC) order.
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** i.e. all those in column 0, sorted by offset, followed by those in
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** column 1, etc.
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**
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** xPhraseNext()
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** See xPhraseFirst above.
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**
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** xPhraseFirstColumn()
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** This function and xPhraseNextColumn() are similar to the xPhraseFirst()
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** and xPhraseNext() APIs described above. The difference is that instead
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** of iterating through all instances of a phrase in the current row, these
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** APIs are used to iterate through the set of columns in the current row
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** that contain one or more instances of a specified phrase. For example:
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**
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** Fts5PhraseIter iter;
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** int iCol;
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** for(pApi->xPhraseFirstColumn(pFts, iPhrase, &iter, &iCol);
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** iCol>=0;
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** pApi->xPhraseNextColumn(pFts, &iter, &iCol)
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** ){
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** // Column iCol contains at least one instance of phrase iPhrase
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** }
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**
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** This API can be quite slow if used with an FTS5 table created with the
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** "detail=none" option. If the FTS5 table is created with either
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** "detail=none" "content=" option (i.e. if it is a contentless table),
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** then this API always iterates through an empty set (all calls to
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** xPhraseFirstColumn() set iCol to -1).
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**
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** The information accessed using this API and its companion
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** xPhraseFirstColumn() may also be obtained using xPhraseFirst/xPhraseNext
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** (or xInst/xInstCount). The chief advantage of this API is that it is
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** significantly more efficient than those alternatives when used with
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** "detail=column" tables.
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**
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** xPhraseNextColumn()
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** See xPhraseFirstColumn above.
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**
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** xQueryToken(pFts5, iPhrase, iToken, ppToken, pnToken)
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** This is used to access token iToken of phrase iPhrase of the current
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** query. Before returning, output parameter *ppToken is set to point
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** to a buffer containing the requested token, and *pnToken to the
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** size of this buffer in bytes.
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**
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** If iPhrase or iToken are less than zero, or if iPhrase is greater than
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** or equal to the number of phrases in the query as reported by
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** xPhraseCount(), or if iToken is equal to or greater than the number of
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** tokens in the phrase, SQLITE_RANGE is returned and *ppToken and *pnToken
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are both zeroed.
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**
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** The output text is not a copy of the query text that specified the
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** token. It is the output of the tokenizer module. For tokendata=1
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** tables, this includes any embedded 0x00 and trailing data.
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**
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** xInstToken(pFts5, iIdx, iToken, ppToken, pnToken)
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** This is used to access token iToken of phrase hit iIdx within the
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** current row. If iIdx is less than zero or greater than or equal to the
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** value returned by xInstCount(), SQLITE_RANGE is returned. Otherwise,
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** output variable (*ppToken) is set to point to a buffer containing the
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** matching document token, and (*pnToken) to the size of that buffer in
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** bytes. This API is not available if the specified token matches a
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** prefix query term. In that case both output variables are always set
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** to 0.
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**
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** The output text is not a copy of the document text that was tokenized.
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** It is the output of the tokenizer module. For tokendata=1 tables, this
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** includes any embedded 0x00 and trailing data.
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**
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** This API can be quite slow if used with an FTS5 table created with the
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** "detail=none" or "detail=column" option.
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**
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** xColumnLocale(pFts5, iIdx, pzLocale, pnLocale)
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** If parameter iCol is less than zero, or greater than or equal to the
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** number of columns in the table, SQLITE_RANGE is returned.
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**
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** Otherwise, this function attempts to retrieve the locale associated
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** with column iCol of the current row. Usually, there is no associated
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** locale, and output parameters (*pzLocale) and (*pnLocale) are set
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** to NULL and 0, respectively. However, if the fts5_locale() function
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** was used to associate a locale with the value when it was inserted
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** into the fts5 table, then (*pzLocale) is set to point to a nul-terminated
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** buffer containing the name of the locale in utf-8 encoding. (*pnLocale)
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** is set to the size in bytes of the buffer, not including the
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** nul-terminator.
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**
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** If successful, SQLITE_OK is returned. Or, if an error occurs, an
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** SQLite error code is returned. The final value of the output parameters
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** is undefined in this case.
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**
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** xTokenize_v2:
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** Tokenize text using the tokenizer belonging to the FTS5 table. This
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** API is the same as the xTokenize() API, except that it allows a tokenizer
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** locale to be specified.
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*/
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struct Fts5ExtensionApi {
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int iVersion; /* Currently always set to 4 */
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void *(*xUserData)(Fts5Context*);
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int (*xColumnCount)(Fts5Context*);
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int (*xRowCount)(Fts5Context*, sqlite3_int64 *pnRow);
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int (*xColumnTotalSize)(Fts5Context*, int iCol, sqlite3_int64 *pnToken);
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int (*xTokenize)(Fts5Context*,
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const char *pText, int nText, /* Text to tokenize */
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void *pCtx, /* Context passed to xToken() */
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int (*xToken)(void*, int, const char*, int, int, int) /* Callback */
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);
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int (*xPhraseCount)(Fts5Context*);
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int (*xPhraseSize)(Fts5Context*, int iPhrase);
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int (*xInstCount)(Fts5Context*, int *pnInst);
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int (*xInst)(Fts5Context*, int iIdx, int *piPhrase, int *piCol, int *piOff);
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sqlite3_int64 (*xRowid)(Fts5Context*);
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int (*xColumnText)(Fts5Context*, int iCol, const char **pz, int *pn);
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int (*xColumnSize)(Fts5Context*, int iCol, int *pnToken);
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int (*xQueryPhrase)(Fts5Context*, int iPhrase, void *pUserData,
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int(*)(const Fts5ExtensionApi*,Fts5Context*,void*)
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);
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int (*xSetAuxdata)(Fts5Context*, void *pAux, void(*xDelete)(void*));
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void *(*xGetAuxdata)(Fts5Context*, int bClear);
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int (*xPhraseFirst)(Fts5Context*, int iPhrase, Fts5PhraseIter*, int*, int*);
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void (*xPhraseNext)(Fts5Context*, Fts5PhraseIter*, int *piCol, int *piOff);
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int (*xPhraseFirstColumn)(Fts5Context*, int iPhrase, Fts5PhraseIter*, int*);
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void (*xPhraseNextColumn)(Fts5Context*, Fts5PhraseIter*, int *piCol);
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/* Below this point are iVersion>=3 only */
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int (*xQueryToken)(Fts5Context*,
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int iPhrase, int iToken,
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const char **ppToken, int *pnToken
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);
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int (*xInstToken)(Fts5Context*, int iIdx, int iToken, const char**, int*);
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/* Below this point are iVersion>=4 only */
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int (*xColumnLocale)(Fts5Context*, int iCol, const char **pz, int *pn);
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int (*xTokenize_v2)(Fts5Context*,
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const char *pText, int nText, /* Text to tokenize */
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const char *pLocale, int nLocale, /* Locale to pass to tokenizer */
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void *pCtx, /* Context passed to xToken() */
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int (*xToken)(void*, int, const char*, int, int, int) /* Callback */
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);
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};
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/*
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** CUSTOM AUXILIARY FUNCTIONS
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*************************************************************************/
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/*************************************************************************
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** CUSTOM TOKENIZERS
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**
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** Applications may also register custom tokenizer types. A tokenizer
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** is registered by providing fts5 with a populated instance of the
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** following structure. All structure methods must be defined, setting
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** any member of the fts5_tokenizer struct to NULL leads to undefined
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** behaviour. The structure methods are expected to function as follows:
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**
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** xCreate:
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** This function is used to allocate and initialize a tokenizer instance.
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** A tokenizer instance is required to actually tokenize text.
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**
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** The first argument passed to this function is a copy of the (void*)
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** pointer provided by the application when the fts5_tokenizer_v2 object
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** was registered with FTS5 (the third argument to xCreateTokenizer()).
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** The second and third arguments are an array of nul-terminated strings
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** containing the tokenizer arguments, if any, specified following the
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** tokenizer name as part of the CREATE VIRTUAL TABLE statement used
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** to create the FTS5 table.
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**
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** The final argument is an output variable. If successful, (*ppOut)
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** should be set to point to the new tokenizer handle and SQLITE_OK
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** returned. If an error occurs, some value other than SQLITE_OK should
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** be returned. In this case, fts5 assumes that the final value of *ppOut
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** is undefined.
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**
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** xDelete:
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** This function is invoked to delete a tokenizer handle previously
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** allocated using xCreate(). Fts5 guarantees that this function will
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** be invoked exactly once for each successful call to xCreate().
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**
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** xTokenize:
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** This function is expected to tokenize the nText byte string indicated
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** 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 third 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>
|
|
**
|
|
** The sixth and seventh arguments passed to xTokenize() - pLocale and
|
|
** nLocale - are a pointer to a buffer containing the locale to use for
|
|
** tokenization (e.g. "en_US") and its size in bytes, respectively. The
|
|
** pLocale buffer is not nul-terminated. pLocale may be passed NULL (in
|
|
** which case nLocale is always 0) to indicate that the tokenizer should
|
|
** use its default locale.
|
|
**
|
|
** 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.
|
|
**
|
|
** If the tokenizer is registered using an fts5_tokenizer_v2 object,
|
|
** then the xTokenize() method has two additional arguments - pLocale
|
|
** and nLocale. These specify the locale that the tokenizer should use
|
|
** for the current request. If pLocale and nLocale are both 0, then the
|
|
** tokenizer should use its default locale. Otherwise, pLocale points to
|
|
** an nLocale byte buffer containing the name of the locale to use as utf-8
|
|
** text. pLocale is not nul-terminated.
|
|
**
|
|
** FTS5_TOKENIZER
|
|
**
|
|
** There is also an fts5_tokenizer object. This is an older, deprecated,
|
|
** version of fts5_tokenizer_v2. It is similar except that:
|
|
**
|
|
** <ul>
|
|
** <li> There is no "iVersion" field, and
|
|
** <li> The xTokenize() method does not take a locale argument.
|
|
** </ul>
|
|
**
|
|
** Legacy fts5_tokenizer tokenizers must be registered using the
|
|
** legacy xCreateTokenizer() function, instead of xCreateTokenizer_v2().
|
|
**
|
|
** Tokenizer implementations registered using either API may be retrieved
|
|
** using both xFindTokenizer() and xFindTokenizer_v2().
|
|
**
|
|
** 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 (3)) or query
|
|
** text (method (2)), not both. Doing so will not cause any errors, but is
|
|
** inefficient.
|
|
*/
|
|
typedef struct Fts5Tokenizer Fts5Tokenizer;
|
|
typedef struct fts5_tokenizer_v2 fts5_tokenizer_v2;
|
|
struct fts5_tokenizer_v2 {
|
|
int iVersion; /* Currently always 2 */
|
|
|
|
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,
|
|
const char *pLocale, int nLocale,
|
|
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 */
|
|
)
|
|
);
|
|
};
|
|
|
|
/*
|
|
** New code should use the fts5_tokenizer_v2 type to define tokenizer
|
|
** implementations. The following type is included for legacy applications
|
|
** that still use it.
|
|
*/
|
|
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 3 */
|
|
|
|
/* Create a new tokenizer */
|
|
int (*xCreateTokenizer)(
|
|
fts5_api *pApi,
|
|
const char *zName,
|
|
void *pUserData,
|
|
fts5_tokenizer *pTokenizer,
|
|
void (*xDestroy)(void*)
|
|
);
|
|
|
|
/* Find an existing tokenizer */
|
|
int (*xFindTokenizer)(
|
|
fts5_api *pApi,
|
|
const char *zName,
|
|
void **ppUserData,
|
|
fts5_tokenizer *pTokenizer
|
|
);
|
|
|
|
/* Create a new auxiliary function */
|
|
int (*xCreateFunction)(
|
|
fts5_api *pApi,
|
|
const char *zName,
|
|
void *pUserData,
|
|
fts5_extension_function xFunction,
|
|
void (*xDestroy)(void*)
|
|
);
|
|
|
|
/* APIs below this point are only available if iVersion>=3 */
|
|
|
|
/* Create a new tokenizer */
|
|
int (*xCreateTokenizer_v2)(
|
|
fts5_api *pApi,
|
|
const char *zName,
|
|
void *pUserData,
|
|
fts5_tokenizer_v2 *pTokenizer,
|
|
void (*xDestroy)(void*)
|
|
);
|
|
|
|
/* Find an existing tokenizer */
|
|
int (*xFindTokenizer_v2)(
|
|
fts5_api *pApi,
|
|
const char *zName,
|
|
void **ppUserData,
|
|
fts5_tokenizer_v2 **ppTokenizer
|
|
);
|
|
};
|
|
|
|
/*
|
|
** END OF REGISTRATION API
|
|
*************************************************************************/
|
|
|
|
#ifdef __cplusplus
|
|
} /* end of the 'extern "C"' block */
|
|
#endif
|
|
|
|
#endif /* _FTS5_H */
|