774 lines
25 KiB
C
774 lines
25 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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#include "fts5Int.h"
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#include <math.h> /* amalgamator: keep */
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/*
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** Object used to iterate through all "coalesced phrase instances" in
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** a single column of the current row. If the phrase instances in the
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** column being considered do not overlap, this object simply iterates
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** through them. Or, if they do overlap (share one or more tokens in
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** common), each set of overlapping instances is treated as a single
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** match. See documentation for the highlight() auxiliary function for
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** details.
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**
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** Usage is:
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**
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** for(rc = fts5CInstIterNext(pApi, pFts, iCol, &iter);
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** (rc==SQLITE_OK && 0==fts5CInstIterEof(&iter);
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** rc = fts5CInstIterNext(&iter)
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** ){
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** printf("instance starts at %d, ends at %d\n", iter.iStart, iter.iEnd);
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** }
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**
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*/
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typedef struct CInstIter CInstIter;
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struct CInstIter {
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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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int iCol; /* Column to search */
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int iInst; /* Next phrase instance index */
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int nInst; /* Total number of phrase instances */
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/* Output variables */
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int iStart; /* First token in coalesced phrase instance */
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int iEnd; /* Last token in coalesced phrase instance */
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};
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/*
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** Advance the iterator to the next coalesced phrase instance. Return
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** an SQLite error code if an error occurs, or SQLITE_OK otherwise.
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*/
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static int fts5CInstIterNext(CInstIter *pIter){
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int rc = SQLITE_OK;
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pIter->iStart = -1;
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pIter->iEnd = -1;
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while( rc==SQLITE_OK && pIter->iInst<pIter->nInst ){
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int ip; int ic; int io;
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rc = pIter->pApi->xInst(pIter->pFts, pIter->iInst, &ip, &ic, &io);
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if( rc==SQLITE_OK ){
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if( ic==pIter->iCol ){
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int iEnd = io - 1 + pIter->pApi->xPhraseSize(pIter->pFts, ip);
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if( pIter->iStart<0 ){
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pIter->iStart = io;
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pIter->iEnd = iEnd;
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}else if( io<=pIter->iEnd ){
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if( iEnd>pIter->iEnd ) pIter->iEnd = iEnd;
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}else{
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break;
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}
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}
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pIter->iInst++;
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}
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}
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return rc;
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}
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/*
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** Initialize the iterator object indicated by the final parameter to
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** iterate through coalesced phrase instances in column iCol.
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*/
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static int fts5CInstIterInit(
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const Fts5ExtensionApi *pApi,
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Fts5Context *pFts,
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int iCol,
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CInstIter *pIter
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){
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int rc;
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memset(pIter, 0, sizeof(CInstIter));
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pIter->pApi = pApi;
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pIter->pFts = pFts;
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pIter->iCol = iCol;
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rc = pApi->xInstCount(pFts, &pIter->nInst);
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if( rc==SQLITE_OK ){
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rc = fts5CInstIterNext(pIter);
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}
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return rc;
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}
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/*************************************************************************
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** Start of highlight() implementation.
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*/
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typedef struct HighlightContext HighlightContext;
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struct HighlightContext {
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/* Constant parameters to fts5HighlightCb() */
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int iRangeStart; /* First token to include */
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int iRangeEnd; /* If non-zero, last token to include */
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const char *zOpen; /* Opening highlight */
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const char *zClose; /* Closing highlight */
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const char *zIn; /* Input text */
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int nIn; /* Size of input text in bytes */
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/* Variables modified by fts5HighlightCb() */
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CInstIter iter; /* Coalesced Instance Iterator */
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int iPos; /* Current token offset in zIn[] */
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int iOff; /* Have copied up to this offset in zIn[] */
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int bOpen; /* True if highlight is open */
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char *zOut; /* Output value */
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};
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/*
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** Append text to the HighlightContext output string - p->zOut. Argument
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** z points to a buffer containing n bytes of text to append. If n is
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** negative, everything up until the first '\0' is appended to the output.
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**
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** If *pRc is set to any value other than SQLITE_OK when this function is
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** called, it is a no-op. If an error (i.e. an OOM condition) is encountered,
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** *pRc is set to an error code before returning.
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*/
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static void fts5HighlightAppend(
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int *pRc,
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HighlightContext *p,
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const char *z, int n
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){
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if( *pRc==SQLITE_OK && z ){
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if( n<0 ) n = (int)strlen(z);
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p->zOut = sqlite3_mprintf("%z%.*s", p->zOut, n, z);
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if( p->zOut==0 ) *pRc = SQLITE_NOMEM;
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}
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}
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/*
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** Tokenizer callback used by implementation of highlight() function.
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*/
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static int fts5HighlightCb(
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void *pContext, /* Pointer to HighlightContext object */
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int tflags, /* Mask of FTS5_TOKEN_* flags */
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const char *pToken, /* Buffer containing token */
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int nToken, /* Size of token in bytes */
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int iStartOff, /* Start byte offset of token */
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int iEndOff /* End byte offset of token */
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){
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HighlightContext *p = (HighlightContext*)pContext;
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int rc = SQLITE_OK;
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int iPos;
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UNUSED_PARAM2(pToken, nToken);
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if( tflags & FTS5_TOKEN_COLOCATED ) return SQLITE_OK;
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iPos = p->iPos++;
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if( p->iRangeEnd>=0 ){
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if( iPos<p->iRangeStart || iPos>p->iRangeEnd ) return SQLITE_OK;
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if( p->iRangeStart && iPos==p->iRangeStart ) p->iOff = iStartOff;
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}
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/* If the parenthesis is open, and this token is not part of the current
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** phrase, and the starting byte offset of this token is past the point
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** that has currently been copied into the output buffer, close the
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** parenthesis. */
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if( p->bOpen
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&& (iPos<=p->iter.iStart || p->iter.iStart<0)
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&& iStartOff>p->iOff
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){
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fts5HighlightAppend(&rc, p, p->zClose, -1);
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p->bOpen = 0;
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}
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/* If this is the start of a new phrase, and the highlight is not open:
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**
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** * copy text from the input up to the start of the phrase, and
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** * open the highlight.
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*/
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if( iPos==p->iter.iStart && p->bOpen==0 ){
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fts5HighlightAppend(&rc, p, &p->zIn[p->iOff], iStartOff - p->iOff);
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fts5HighlightAppend(&rc, p, p->zOpen, -1);
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p->iOff = iStartOff;
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p->bOpen = 1;
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}
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if( iPos==p->iter.iEnd ){
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if( p->bOpen==0 ){
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assert( p->iRangeEnd>=0 );
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fts5HighlightAppend(&rc, p, p->zOpen, -1);
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p->bOpen = 1;
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}
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fts5HighlightAppend(&rc, p, &p->zIn[p->iOff], iEndOff - p->iOff);
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p->iOff = iEndOff;
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if( rc==SQLITE_OK ){
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rc = fts5CInstIterNext(&p->iter);
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}
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}
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if( iPos==p->iRangeEnd ){
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if( p->bOpen ){
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if( p->iter.iStart>=0 && iPos>=p->iter.iStart ){
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fts5HighlightAppend(&rc, p, &p->zIn[p->iOff], iEndOff - p->iOff);
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p->iOff = iEndOff;
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}
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fts5HighlightAppend(&rc, p, p->zClose, -1);
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p->bOpen = 0;
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}
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fts5HighlightAppend(&rc, p, &p->zIn[p->iOff], iEndOff - p->iOff);
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p->iOff = iEndOff;
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}
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return rc;
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}
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/*
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** Implementation of highlight() function.
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*/
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static void fts5HighlightFunction(
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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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HighlightContext ctx;
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int rc;
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int iCol;
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if( nVal!=3 ){
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const char *zErr = "wrong number of arguments to function highlight()";
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sqlite3_result_error(pCtx, zErr, -1);
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return;
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}
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iCol = sqlite3_value_int(apVal[0]);
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memset(&ctx, 0, sizeof(HighlightContext));
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ctx.zOpen = (const char*)sqlite3_value_text(apVal[1]);
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ctx.zClose = (const char*)sqlite3_value_text(apVal[2]);
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ctx.iRangeEnd = -1;
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rc = pApi->xColumnText(pFts, iCol, &ctx.zIn, &ctx.nIn);
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if( rc==SQLITE_RANGE ){
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sqlite3_result_text(pCtx, "", -1, SQLITE_STATIC);
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rc = SQLITE_OK;
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}else if( ctx.zIn ){
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const char *pLoc = 0; /* Locale of column iCol */
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int nLoc = 0; /* Size of pLoc in bytes */
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if( rc==SQLITE_OK ){
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rc = fts5CInstIterInit(pApi, pFts, iCol, &ctx.iter);
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}
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if( rc==SQLITE_OK ){
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rc = pApi->xColumnLocale(pFts, iCol, &pLoc, &nLoc);
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}
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if( rc==SQLITE_OK ){
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rc = pApi->xTokenize_v2(
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pFts, ctx.zIn, ctx.nIn, pLoc, nLoc, (void*)&ctx, fts5HighlightCb
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);
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}
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if( ctx.bOpen ){
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fts5HighlightAppend(&rc, &ctx, ctx.zClose, -1);
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}
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fts5HighlightAppend(&rc, &ctx, &ctx.zIn[ctx.iOff], ctx.nIn - ctx.iOff);
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if( rc==SQLITE_OK ){
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sqlite3_result_text(pCtx, (const char*)ctx.zOut, -1, SQLITE_TRANSIENT);
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}
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sqlite3_free(ctx.zOut);
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}
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if( rc!=SQLITE_OK ){
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sqlite3_result_error_code(pCtx, rc);
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}
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}
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/*
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** End of highlight() implementation.
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**************************************************************************/
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/*
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** Context object passed to the fts5SentenceFinderCb() function.
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*/
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typedef struct Fts5SFinder Fts5SFinder;
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struct Fts5SFinder {
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int iPos; /* Current token position */
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int nFirstAlloc; /* Allocated size of aFirst[] */
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int nFirst; /* Number of entries in aFirst[] */
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int *aFirst; /* Array of first token in each sentence */
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const char *zDoc; /* Document being tokenized */
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};
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/*
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** Add an entry to the Fts5SFinder.aFirst[] array. Grow the array if
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** necessary. Return SQLITE_OK if successful, or SQLITE_NOMEM if an
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** error occurs.
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*/
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static int fts5SentenceFinderAdd(Fts5SFinder *p, int iAdd){
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if( p->nFirstAlloc==p->nFirst ){
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int nNew = p->nFirstAlloc ? p->nFirstAlloc*2 : 64;
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int *aNew;
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aNew = (int*)sqlite3_realloc64(p->aFirst, nNew*sizeof(int));
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if( aNew==0 ) return SQLITE_NOMEM;
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p->aFirst = aNew;
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p->nFirstAlloc = nNew;
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}
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p->aFirst[p->nFirst++] = iAdd;
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return SQLITE_OK;
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}
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/*
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** This function is an xTokenize() callback used by the auxiliary snippet()
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** function. Its job is to identify tokens that are the first in a sentence.
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** For each such token, an entry is added to the SFinder.aFirst[] array.
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*/
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static int fts5SentenceFinderCb(
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void *pContext, /* Pointer to HighlightContext object */
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int tflags, /* Mask of FTS5_TOKEN_* flags */
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const char *pToken, /* Buffer containing token */
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int nToken, /* Size of token in bytes */
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int iStartOff, /* Start offset of token */
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int iEndOff /* End offset of token */
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){
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int rc = SQLITE_OK;
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UNUSED_PARAM2(pToken, nToken);
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UNUSED_PARAM(iEndOff);
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if( (tflags & FTS5_TOKEN_COLOCATED)==0 ){
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Fts5SFinder *p = (Fts5SFinder*)pContext;
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if( p->iPos>0 ){
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int i;
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char c = 0;
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for(i=iStartOff-1; i>=0; i--){
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c = p->zDoc[i];
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if( c!=' ' && c!='\t' && c!='\n' && c!='\r' ) break;
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}
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if( i!=iStartOff-1 && (c=='.' || c==':') ){
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rc = fts5SentenceFinderAdd(p, p->iPos);
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}
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}else{
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rc = fts5SentenceFinderAdd(p, 0);
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}
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p->iPos++;
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}
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return rc;
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}
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static int fts5SnippetScore(
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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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int nDocsize, /* Size of column in tokens */
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unsigned char *aSeen, /* Array with one element per query phrase */
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int iCol, /* Column to score */
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int iPos, /* Starting offset to score */
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int nToken, /* Max tokens per snippet */
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int *pnScore, /* OUT: Score */
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int *piPos /* OUT: Adjusted offset */
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){
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int rc;
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int i;
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int ip = 0;
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int ic = 0;
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int iOff = 0;
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int iFirst = -1;
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int nInst;
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int nScore = 0;
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int iLast = 0;
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sqlite3_int64 iEnd = (sqlite3_int64)iPos + nToken;
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rc = pApi->xInstCount(pFts, &nInst);
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for(i=0; i<nInst && rc==SQLITE_OK; i++){
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rc = pApi->xInst(pFts, i, &ip, &ic, &iOff);
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if( rc==SQLITE_OK && ic==iCol && iOff>=iPos && iOff<iEnd ){
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nScore += (aSeen[ip] ? 1 : 1000);
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aSeen[ip] = 1;
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if( iFirst<0 ) iFirst = iOff;
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iLast = iOff + pApi->xPhraseSize(pFts, ip);
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}
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}
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*pnScore = nScore;
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if( piPos ){
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sqlite3_int64 iAdj = iFirst - (nToken - (iLast-iFirst)) / 2;
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if( (iAdj+nToken)>nDocsize ) iAdj = nDocsize - nToken;
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if( iAdj<0 ) iAdj = 0;
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*piPos = (int)iAdj;
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}
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return rc;
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}
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/*
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** Return the value in pVal interpreted as utf-8 text. Except, if pVal
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** contains a NULL value, return a pointer to a static string zero
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** bytes in length instead of a NULL pointer.
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*/
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static const char *fts5ValueToText(sqlite3_value *pVal){
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const char *zRet = (const char*)sqlite3_value_text(pVal);
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return zRet ? zRet : "";
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}
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/*
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** Implementation of snippet() function.
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*/
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static void fts5SnippetFunction(
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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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HighlightContext ctx;
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int rc = SQLITE_OK; /* Return code */
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int iCol; /* 1st argument to snippet() */
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const char *zEllips; /* 4th argument to snippet() */
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int nToken; /* 5th argument to snippet() */
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int nInst = 0; /* Number of instance matches this row */
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int i; /* Used to iterate through instances */
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int nPhrase; /* Number of phrases in query */
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unsigned char *aSeen; /* Array of "seen instance" flags */
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int iBestCol; /* Column containing best snippet */
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int iBestStart = 0; /* First token of best snippet */
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int nBestScore = 0; /* Score of best snippet */
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int nColSize = 0; /* Total size of iBestCol in tokens */
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Fts5SFinder sFinder; /* Used to find the beginnings of sentences */
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int nCol;
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if( nVal!=5 ){
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const char *zErr = "wrong number of arguments to function snippet()";
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sqlite3_result_error(pCtx, zErr, -1);
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return;
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}
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nCol = pApi->xColumnCount(pFts);
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memset(&ctx, 0, sizeof(HighlightContext));
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iCol = sqlite3_value_int(apVal[0]);
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ctx.zOpen = fts5ValueToText(apVal[1]);
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ctx.zClose = fts5ValueToText(apVal[2]);
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ctx.iRangeEnd = -1;
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zEllips = fts5ValueToText(apVal[3]);
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nToken = sqlite3_value_int(apVal[4]);
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iBestCol = (iCol>=0 ? iCol : 0);
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nPhrase = pApi->xPhraseCount(pFts);
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aSeen = sqlite3_malloc(nPhrase);
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if( aSeen==0 ){
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rc = SQLITE_NOMEM;
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}
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if( rc==SQLITE_OK ){
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rc = pApi->xInstCount(pFts, &nInst);
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}
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memset(&sFinder, 0, sizeof(Fts5SFinder));
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for(i=0; i<nCol; i++){
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if( iCol<0 || iCol==i ){
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const char *pLoc = 0; /* Locale of column iCol */
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int nLoc = 0; /* Size of pLoc in bytes */
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int nDoc;
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int nDocsize;
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int ii;
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sFinder.iPos = 0;
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sFinder.nFirst = 0;
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rc = pApi->xColumnText(pFts, i, &sFinder.zDoc, &nDoc);
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if( rc!=SQLITE_OK ) break;
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rc = pApi->xColumnLocale(pFts, i, &pLoc, &nLoc);
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if( rc!=SQLITE_OK ) break;
|
|
rc = pApi->xTokenize_v2(pFts,
|
|
sFinder.zDoc, nDoc, pLoc, nLoc, (void*)&sFinder, fts5SentenceFinderCb
|
|
);
|
|
if( rc!=SQLITE_OK ) break;
|
|
rc = pApi->xColumnSize(pFts, i, &nDocsize);
|
|
if( rc!=SQLITE_OK ) break;
|
|
|
|
for(ii=0; rc==SQLITE_OK && ii<nInst; ii++){
|
|
int ip, ic, io;
|
|
int iAdj;
|
|
int nScore;
|
|
int jj;
|
|
|
|
rc = pApi->xInst(pFts, ii, &ip, &ic, &io);
|
|
if( ic!=i ) continue;
|
|
if( io>nDocsize ) rc = FTS5_CORRUPT;
|
|
if( rc!=SQLITE_OK ) continue;
|
|
memset(aSeen, 0, nPhrase);
|
|
rc = fts5SnippetScore(pApi, pFts, nDocsize, aSeen, i,
|
|
io, nToken, &nScore, &iAdj
|
|
);
|
|
if( rc==SQLITE_OK && nScore>nBestScore ){
|
|
nBestScore = nScore;
|
|
iBestCol = i;
|
|
iBestStart = iAdj;
|
|
nColSize = nDocsize;
|
|
}
|
|
|
|
if( rc==SQLITE_OK && sFinder.nFirst && nDocsize>nToken ){
|
|
for(jj=0; jj<(sFinder.nFirst-1); jj++){
|
|
if( sFinder.aFirst[jj+1]>io ) break;
|
|
}
|
|
|
|
if( sFinder.aFirst[jj]<io ){
|
|
memset(aSeen, 0, nPhrase);
|
|
rc = fts5SnippetScore(pApi, pFts, nDocsize, aSeen, i,
|
|
sFinder.aFirst[jj], nToken, &nScore, 0
|
|
);
|
|
|
|
nScore += (sFinder.aFirst[jj]==0 ? 120 : 100);
|
|
if( rc==SQLITE_OK && nScore>nBestScore ){
|
|
nBestScore = nScore;
|
|
iBestCol = i;
|
|
iBestStart = sFinder.aFirst[jj];
|
|
nColSize = nDocsize;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
if( rc==SQLITE_OK ){
|
|
rc = pApi->xColumnText(pFts, iBestCol, &ctx.zIn, &ctx.nIn);
|
|
}
|
|
if( rc==SQLITE_OK && nColSize==0 ){
|
|
rc = pApi->xColumnSize(pFts, iBestCol, &nColSize);
|
|
}
|
|
if( ctx.zIn ){
|
|
const char *pLoc = 0; /* Locale of column iBestCol */
|
|
int nLoc = 0; /* Bytes in pLoc */
|
|
|
|
if( rc==SQLITE_OK ){
|
|
rc = fts5CInstIterInit(pApi, pFts, iBestCol, &ctx.iter);
|
|
}
|
|
|
|
ctx.iRangeStart = iBestStart;
|
|
ctx.iRangeEnd = iBestStart + nToken - 1;
|
|
|
|
if( iBestStart>0 ){
|
|
fts5HighlightAppend(&rc, &ctx, zEllips, -1);
|
|
}
|
|
|
|
/* Advance iterator ctx.iter so that it points to the first coalesced
|
|
** phrase instance at or following position iBestStart. */
|
|
while( ctx.iter.iStart>=0 && ctx.iter.iStart<iBestStart && rc==SQLITE_OK ){
|
|
rc = fts5CInstIterNext(&ctx.iter);
|
|
}
|
|
|
|
if( rc==SQLITE_OK ){
|
|
rc = pApi->xColumnLocale(pFts, iBestCol, &pLoc, &nLoc);
|
|
}
|
|
if( rc==SQLITE_OK ){
|
|
rc = pApi->xTokenize_v2(
|
|
pFts, ctx.zIn, ctx.nIn, pLoc, nLoc, (void*)&ctx,fts5HighlightCb
|
|
);
|
|
}
|
|
if( ctx.bOpen ){
|
|
fts5HighlightAppend(&rc, &ctx, ctx.zClose, -1);
|
|
}
|
|
if( ctx.iRangeEnd>=(nColSize-1) ){
|
|
fts5HighlightAppend(&rc, &ctx, &ctx.zIn[ctx.iOff], ctx.nIn - ctx.iOff);
|
|
}else{
|
|
fts5HighlightAppend(&rc, &ctx, zEllips, -1);
|
|
}
|
|
}
|
|
if( rc==SQLITE_OK ){
|
|
sqlite3_result_text(pCtx, (const char*)ctx.zOut, -1, SQLITE_TRANSIENT);
|
|
}else{
|
|
sqlite3_result_error_code(pCtx, rc);
|
|
}
|
|
sqlite3_free(ctx.zOut);
|
|
sqlite3_free(aSeen);
|
|
sqlite3_free(sFinder.aFirst);
|
|
}
|
|
|
|
/************************************************************************/
|
|
|
|
/*
|
|
** The first time the bm25() function is called for a query, an instance
|
|
** of the following structure is allocated and populated.
|
|
*/
|
|
typedef struct Fts5Bm25Data Fts5Bm25Data;
|
|
struct Fts5Bm25Data {
|
|
int nPhrase; /* Number of phrases in query */
|
|
double avgdl; /* Average number of tokens in each row */
|
|
double *aIDF; /* IDF for each phrase */
|
|
double *aFreq; /* Array used to calculate phrase freq. */
|
|
};
|
|
|
|
/*
|
|
** Callback used by fts5Bm25GetData() to count the number of rows in the
|
|
** table matched by each individual phrase within the query.
|
|
*/
|
|
static int fts5CountCb(
|
|
const Fts5ExtensionApi *pApi,
|
|
Fts5Context *pFts,
|
|
void *pUserData /* Pointer to sqlite3_int64 variable */
|
|
){
|
|
sqlite3_int64 *pn = (sqlite3_int64*)pUserData;
|
|
UNUSED_PARAM2(pApi, pFts);
|
|
(*pn)++;
|
|
return SQLITE_OK;
|
|
}
|
|
|
|
/*
|
|
** Set *ppData to point to the Fts5Bm25Data object for the current query.
|
|
** If the object has not already been allocated, allocate and populate it
|
|
** now.
|
|
*/
|
|
static int fts5Bm25GetData(
|
|
const Fts5ExtensionApi *pApi,
|
|
Fts5Context *pFts,
|
|
Fts5Bm25Data **ppData /* OUT: bm25-data object for this query */
|
|
){
|
|
int rc = SQLITE_OK; /* Return code */
|
|
Fts5Bm25Data *p; /* Object to return */
|
|
|
|
p = (Fts5Bm25Data*)pApi->xGetAuxdata(pFts, 0);
|
|
if( p==0 ){
|
|
int nPhrase; /* Number of phrases in query */
|
|
sqlite3_int64 nRow = 0; /* Number of rows in table */
|
|
sqlite3_int64 nToken = 0; /* Number of tokens in table */
|
|
sqlite3_int64 nByte; /* Bytes of space to allocate */
|
|
int i;
|
|
|
|
/* Allocate the Fts5Bm25Data object */
|
|
nPhrase = pApi->xPhraseCount(pFts);
|
|
nByte = sizeof(Fts5Bm25Data) + nPhrase*2*sizeof(double);
|
|
p = (Fts5Bm25Data*)sqlite3_malloc64(nByte);
|
|
if( p==0 ){
|
|
rc = SQLITE_NOMEM;
|
|
}else{
|
|
memset(p, 0, (size_t)nByte);
|
|
p->nPhrase = nPhrase;
|
|
p->aIDF = (double*)&p[1];
|
|
p->aFreq = &p->aIDF[nPhrase];
|
|
}
|
|
|
|
/* Calculate the average document length for this FTS5 table */
|
|
if( rc==SQLITE_OK ) rc = pApi->xRowCount(pFts, &nRow);
|
|
assert( rc!=SQLITE_OK || nRow>0 );
|
|
if( rc==SQLITE_OK ) rc = pApi->xColumnTotalSize(pFts, -1, &nToken);
|
|
if( rc==SQLITE_OK ) p->avgdl = (double)nToken / (double)nRow;
|
|
|
|
/* Calculate an IDF for each phrase in the query */
|
|
for(i=0; rc==SQLITE_OK && i<nPhrase; i++){
|
|
sqlite3_int64 nHit = 0;
|
|
rc = pApi->xQueryPhrase(pFts, i, (void*)&nHit, fts5CountCb);
|
|
if( rc==SQLITE_OK ){
|
|
/* Calculate the IDF (Inverse Document Frequency) for phrase i.
|
|
** This is done using the standard BM25 formula as found on wikipedia:
|
|
**
|
|
** IDF = log( (N - nHit + 0.5) / (nHit + 0.5) )
|
|
**
|
|
** where "N" is the total number of documents in the set and nHit
|
|
** is the number that contain at least one instance of the phrase
|
|
** under consideration.
|
|
**
|
|
** The problem with this is that if (N < 2*nHit), the IDF is
|
|
** negative. Which is undesirable. So the mimimum allowable IDF is
|
|
** (1e-6) - roughly the same as a term that appears in just over
|
|
** half of set of 5,000,000 documents. */
|
|
double idf = log( (nRow - nHit + 0.5) / (nHit + 0.5) );
|
|
if( idf<=0.0 ) idf = 1e-6;
|
|
p->aIDF[i] = idf;
|
|
}
|
|
}
|
|
|
|
if( rc!=SQLITE_OK ){
|
|
sqlite3_free(p);
|
|
}else{
|
|
rc = pApi->xSetAuxdata(pFts, p, sqlite3_free);
|
|
}
|
|
if( rc!=SQLITE_OK ) p = 0;
|
|
}
|
|
*ppData = p;
|
|
return rc;
|
|
}
|
|
|
|
/*
|
|
** Implementation of bm25() function.
|
|
*/
|
|
static void fts5Bm25Function(
|
|
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 */
|
|
){
|
|
const double k1 = 1.2; /* Constant "k1" from BM25 formula */
|
|
const double b = 0.75; /* Constant "b" from BM25 formula */
|
|
int rc; /* Error code */
|
|
double score = 0.0; /* SQL function return value */
|
|
Fts5Bm25Data *pData; /* Values allocated/calculated once only */
|
|
int i; /* Iterator variable */
|
|
int nInst = 0; /* Value returned by xInstCount() */
|
|
double D = 0.0; /* Total number of tokens in row */
|
|
double *aFreq = 0; /* Array of phrase freq. for current row */
|
|
|
|
/* Calculate the phrase frequency (symbol "f(qi,D)" in the documentation)
|
|
** for each phrase in the query for the current row. */
|
|
rc = fts5Bm25GetData(pApi, pFts, &pData);
|
|
if( rc==SQLITE_OK ){
|
|
aFreq = pData->aFreq;
|
|
memset(aFreq, 0, sizeof(double) * pData->nPhrase);
|
|
rc = pApi->xInstCount(pFts, &nInst);
|
|
}
|
|
for(i=0; rc==SQLITE_OK && i<nInst; i++){
|
|
int ip; int ic; int io;
|
|
rc = pApi->xInst(pFts, i, &ip, &ic, &io);
|
|
if( rc==SQLITE_OK ){
|
|
double w = (nVal > ic) ? sqlite3_value_double(apVal[ic]) : 1.0;
|
|
aFreq[ip] += w;
|
|
}
|
|
}
|
|
|
|
/* Figure out the total size of the current row in tokens. */
|
|
if( rc==SQLITE_OK ){
|
|
int nTok;
|
|
rc = pApi->xColumnSize(pFts, -1, &nTok);
|
|
D = (double)nTok;
|
|
}
|
|
|
|
/* Determine and return the BM25 score for the current row. Or, if an
|
|
** error has occurred, throw an exception. */
|
|
if( rc==SQLITE_OK ){
|
|
for(i=0; i<pData->nPhrase; i++){
|
|
score += pData->aIDF[i] * (
|
|
( aFreq[i] * (k1 + 1.0) ) /
|
|
( aFreq[i] + k1 * (1 - b + b * D / pData->avgdl) )
|
|
);
|
|
}
|
|
sqlite3_result_double(pCtx, -1.0 * score);
|
|
}else{
|
|
sqlite3_result_error_code(pCtx, rc);
|
|
}
|
|
}
|
|
|
|
int sqlite3Fts5AuxInit(fts5_api *pApi){
|
|
struct Builtin {
|
|
const char *zFunc; /* Function name (nul-terminated) */
|
|
void *pUserData; /* User-data pointer */
|
|
fts5_extension_function xFunc;/* Callback function */
|
|
void (*xDestroy)(void*); /* Destructor function */
|
|
} aBuiltin [] = {
|
|
{ "snippet", 0, fts5SnippetFunction, 0 },
|
|
{ "highlight", 0, fts5HighlightFunction, 0 },
|
|
{ "bm25", 0, fts5Bm25Function, 0 },
|
|
};
|
|
int rc = SQLITE_OK; /* Return code */
|
|
int i; /* To iterate through builtin functions */
|
|
|
|
for(i=0; rc==SQLITE_OK && i<ArraySize(aBuiltin); i++){
|
|
rc = pApi->xCreateFunction(pApi,
|
|
aBuiltin[i].zFunc,
|
|
aBuiltin[i].pUserData,
|
|
aBuiltin[i].xFunc,
|
|
aBuiltin[i].xDestroy
|
|
);
|
|
}
|
|
|
|
return rc;
|
|
}
|