If a token within an FTS query is prefixed with a '^' character, it must be the first token in a column of data to match.

FossilOrigin-Name: 63ac33c860eb32ce96699f06bf83121cec2ffaca

ext/fts3/fts3.c

@@ -2347,6 +2347,67 @@ static void fts3DoclistPhraseMerge(
   *pnRight = p - aOut;
 }
 
+/*
+** When this function is called, pList points to a doclist containing position
+** data, length *pnList bytes. This removes all entries from the doclist that
+** do not correspond to the first token in a column and overwrites pList
+** with the result. *pnList is set to the length of the new doclist before
+** returning.
+**
+** If bDescDoclist is true, then both the input and output are in descending
+** order. Otherwise, ascending.
+*/
+static void fts3DoclistFirstFilter(
+  int bDescDoclist,               /* True if pList is a descending doclist */
+  char *pList,                    /* Buffer containing doclist */
+  int *pnList                     /* IN/OUT: Size of doclist */
+){
+  char *p = pList;
+  char *pOut = pList;
+  char *pEnd = &pList[*pnList];
+
+  sqlite3_int64 iDoc;
+  sqlite3_int64 iPrev;
+  int bFirstOut = 0;
+
+  fts3GetDeltaVarint3(&p, pEnd, 0, &iDoc);
+  while( p ){
+    int bWritten = 0;
+    if( *p!=0x01 ){
+      if( *p==0x02 ){
+        fts3PutDeltaVarint3(&pOut, bDescDoclist, &iPrev, &bFirstOut, iDoc); 
+        *pOut++ = 0x02;
+        bWritten = 1;
+      }
+      fts3ColumnlistCopy(0, &p);
+    }
+
+    while( *p==0x01 ){
+      sqlite3_int64 iCol;
+      p++;
+      p += sqlite3Fts3GetVarint(p, &iCol);
+      if( *p==0x02 ){
+        if( bWritten==0 ){
+          fts3PutDeltaVarint3(&pOut, bDescDoclist, &iPrev, &bFirstOut, iDoc); 
+          bWritten = 1;
+        }
+        pOut += sqlite3Fts3PutVarint(pOut, iCol);
+        *pOut++ = 0x02;
+      }
+      fts3ColumnlistCopy(0, &p);
+    }
+    if( bWritten ){
+      *pOut++ = 0x00;
+    }
+
+    assert( *p==0x00 );
+    p++;
+    fts3GetDeltaVarint3(&p, pEnd, bDescDoclist, &iDoc);
+  }
+
+  *pnList = (pOut - pList);
+}
+
 
 /*
 ** Merge all doclists in the TermSelect.aaOutput[] array into a single
@@ -3518,6 +3579,10 @@ static void fts3EvalPhraseMergeToken(
 ){
   assert( iToken!=p->iDoclistToken );
 
+  if( p->aToken[iToken].bFirst ){
+    fts3DoclistFirstFilter(pTab->bDescIdx, pList, &nList);
+  }
+
   if( pList==0 ){
     sqlite3_free(p->doclist.aAll);
     p->doclist.aAll = 0;
@@ -3721,6 +3786,7 @@ static int fts3EvalPhraseStart(Fts3Cursor *pCsr, int bOptOk, Fts3Phrase *p){
    && p->nToken==1 
    && pFirst->pSegcsr 
    && pFirst->pSegcsr->bLookup 
+   && pFirst->bFirst==0
   ){
     /* Use the incremental approach. */
     int iCol = (p->iColumn >= pTab->nColumn ? -1 : p->iColumn);

ext/fts3/fts3Int.h

@@ -310,6 +310,7 @@ struct Fts3PhraseToken {
   char *z;                        /* Text of the token */
   int n;                          /* Number of bytes in buffer z */
   int isPrefix;                   /* True if token ends with a "*" character */
+  int bFirst;                     /* True if token must appear at position 0 */
 
   /* Variables above this point are populated when the expression is
   ** parsed (by code in fts3_expr.c). Below this point the variables are

ext/fts3/fts3_expr.c

@@ -180,9 +180,21 @@ static int getNextToken(
           pRet->pPhrase->aToken[0].isPrefix = 1;
           iEnd++;
         }
-        if( !sqlite3_fts3_enable_parentheses && iStart>0 && z[iStart-1]=='-' ){
-          pParse->isNot = 1;
+
+        while( 1 ){
+          if( !sqlite3_fts3_enable_parentheses 
+           && iStart>0 && z[iStart-1]=='-' 
+          ){
+            pParse->isNot = 1;
+            iStart--;
+          }else if( iStart>0 && z[iStart-1]=='^' ){
+            pRet->pPhrase->aToken[0].bFirst = 1;
+            iStart--;
+          }else{
+            break;
+          }
         }
+
       }
       nConsumed = iEnd;
     }
@@ -281,6 +293,7 @@ static int getNextString(
 
         pToken->n = nByte;
         pToken->isPrefix = (iEnd<nInput && zInput[iEnd]=='*');
+        pToken->bFirst = (iBegin>0 && zInput[iBegin-1]=='^');
         nToken = ii+1;
       }
     }

ext/fts3/fts3_write.c

@@ -3117,6 +3117,7 @@ int sqlite3Fts3CacheDeferredDoclists(Fts3Cursor *pCsr){
         for(pDef=pCsr->pDeferred; pDef && rc==SQLITE_OK; pDef=pDef->pNext){
           Fts3PhraseToken *pPT = pDef->pToken;
           if( (pDef->iCol>=p->nColumn || pDef->iCol==i)
+           && (pPT->bFirst==0 || iPos==0)
            && (pPT->n==nToken || (pPT->isPrefix && pPT->n<nToken))
            && (0==memcmp(zToken, pPT->z, pPT->n))
           ){