Reduce the number of branches that need to be tested in the

explainIndexRange() function of where.c.

FossilOrigin-Name: 6fdae9a635a43e1bf7e4a480de1413064732c6b0

manifest

@@ -1,5 +1,8 @@
-C Use\s"COMPOUND"\sinstead\sof\s"COMPOSITE"\sin\sthe\sEXPLAIN\sQUERY\sPLAN\soutput\sto\sdescribe\sUNION,\sUNION\sALL,\sEXCEPT\sand\sINTERSECT\soperations.
-D 2010-11-11T17:48:51
+-----BEGIN PGP SIGNED MESSAGE-----
+Hash: SHA1
+
+C Reduce\sthe\snumber\sof\sbranches\sthat\sneed\sto\sbe\stested\sin\sthe\nexplainIndexRange()\sfunction\sof\swhere.c.
+D 2010-11-12T15:36:00
 F Makefile.arm-wince-mingw32ce-gcc d6df77f1f48d690bd73162294bbba7f59507c72f
 F Makefile.in e7a59672eaeb04408d1fa8501618d7501a3c5e39
 F Makefile.linux-gcc 91d710bdc4998cb015f39edf3cb314ec4f4d7e23
@@ -239,7 +242,7 @@ F src/vtab.c b297e8fa656ab5e66244ab15680d68db0adbec30
 F src/wal.c f26b8d297bd11cb792e609917f9d4c6718ac8e0e
 F src/wal.h c1aac6593a0b02b15dc625987e619edeab39292e
 F src/walker.c 3112bb3afe1d85dc52317cb1d752055e9a781f8f
-F src/where.c 6c1905c835935d6915ccd24506a3acbdc3eba784
+F src/where.c 2a5a0c68cc6c646f5835d484416480f25c9235e9
 F test/aggerror.test a867e273ef9e3d7919f03ef4f0e8c0d2767944f2
 F test/alias.test 4529fbc152f190268a15f9384a5651bbbabc9d87
 F test/all.test 6745008c144bd2956d58864d21f7b304689c1cce
@@ -886,7 +889,14 @@ F tool/speedtest2.tcl ee2149167303ba8e95af97873c575c3e0fab58ff
 F tool/speedtest8.c 2902c46588c40b55661e471d7a86e4dd71a18224
 F tool/speedtest8inst1.c 293327bc76823f473684d589a8160bde1f52c14e
 F tool/vdbe-compress.tcl d70ea6d8a19e3571d7ab8c9b75cba86d1173ff0f
-P 00fb8468b5f2c48a3c91b86803bf306a0331496f
-R 64ead24f61500a4f0593c355fdf08678
-U dan
-Z a73a264298070e2a412f911e555db5e3
+P 28643b85d93d27a44b9370e4087efa8fa2af7f8e
+R 25128c3b1a26bfb5be33069710cfa1ff
+U drh
+Z 1b2d006e34f432619cd673c63b9961c1
+-----BEGIN PGP SIGNATURE-----
+Version: GnuPG v1.4.6 (GNU/Linux)
+
+iD8DBQFM3V7koxKgR168RlERAgxFAJ9v6b1y9uIi2fQKQ0CrbcPW8tmodACfVVag
+Rh8WHmMKMaxcSxUJii+hZlQ=
+=KoLX
+-----END PGP SIGNATURE-----

manifest.uuid

@@ -1 +1 @@
-28643b85d93d27a44b9370e4087efa8fa2af7f8e
+6fdae9a635a43e1bf7e4a480de1413064732c6b0

src/where.c

@@ -3131,6 +3131,26 @@ static int codeAllEqualityTerms(
 }
 
 #ifndef SQLITE_OMIT_EXPLAIN
+/*
+** This routine is a helper for explainIndexRange() below
+**
+** pStr holds the text of an expression that we are building up one term
+** at a time.  This routine adds a new term to the end of the expression.
+** Terms are separated by AND so add the "AND" text for second and subsequent
+** terms only.
+*/
+static void explainAppendTerm(
+  StrAccum *pStr,             /* The text expression being built */
+  int iTerm,                  /* Index of this term.  First is zero */
+  const char *zColumn,        /* Name of the column */
+  const char *zOp             /* Name of the operator */
+){
+  if( iTerm ) sqlite3StrAccumAppend(pStr, " AND ", 5);
+  sqlite3StrAccumAppend(pStr, zColumn, -1);
+  sqlite3StrAccumAppend(pStr, zOp, 1);
+  sqlite3StrAccumAppend(pStr, "?", 1);
+}
+
 /*
 ** Argument pLevel describes a strategy for scanning table pTab. This 
 ** function returns a pointer to a string buffer containing a description
@@ -3154,34 +3174,29 @@ static char *explainIndexRange(sqlite3 *db, WhereLevel *pLevel, Table *pTab){
   WherePlan *pPlan = &pLevel->plan;
   Index *pIndex = pPlan->u.pIdx;
   int nEq = pPlan->nEq;
-  char *zRet = 0;
-  int i;
+  int i, j;
+  Column *aCol = pTab->aCol;
+  int *aiColumn = pIndex->aiColumn;
+  StrAccum txt;
 
+  if( nEq==0 && (pPlan->wsFlags & (WHERE_BTM_LIMIT|WHERE_TOP_LIMIT))==0 ){
+    return 0;
+  }
+  sqlite3StrAccumInit(&txt, 0, 0, SQLITE_MAX_LENGTH);
+  sqlite3StrAccumAppend(&txt, " (", 2);
   for(i=0; i<nEq; i++){
-    zRet = sqlite3MAppendf(db, zRet, 
-        "%s%s%s=?", (zRet?zRet:""), (zRet?" AND ":""), 
-        pTab->aCol[pIndex->aiColumn[i]].zName
-    );
+    explainAppendTerm(&txt, i, aCol[aiColumn[i]].zName, "=");
   }
 
+  j = i;
   if( pPlan->wsFlags&WHERE_BTM_LIMIT ){
-    zRet = sqlite3MAppendf(db, zRet,
-        "%s%s%s>?", (zRet?zRet:""), (zRet?" AND ":""),
-        pTab->aCol[pIndex->aiColumn[i]].zName
-    );
+    explainAppendTerm(&txt, i++, aCol[aiColumn[j]].zName, ">");
   }
   if( pPlan->wsFlags&WHERE_TOP_LIMIT ){
-    zRet = sqlite3MAppendf(db, zRet,
-        "%s%s%s<?", (zRet?zRet:""), (zRet?" AND ":""), 
-        pTab->aCol[pIndex->aiColumn[i]].zName
-    );
+    explainAppendTerm(&txt, i, aCol[aiColumn[j]].zName, "<");
   }
-
-  if( zRet ){
-    zRet = sqlite3MAppendf(db, zRet, " (%s)", zRet);
-  }
-
-  return zRet;
+  sqlite3StrAccumAppend(&txt, ")", 1);
+  return sqlite3StrAccumFinish(&txt);
 }
 
 /*