Fix the Parse.aColCache column cache so that all of the valid entries are

in the first Parse.nColCache slots.

FossilOrigin-Name: 6028502059ccbd3699637b7a70a6d8ce1b7c3dad

1 files changed, 52 insertions, 74 deletions

diff --git a/src/expr.c b/src/expr.c
index e8c245ec4..0640029cb 100644
--- a/src/expr.c
+++ b/src/expr.c
@@ -2964,32 +2964,19 @@ static void codeInteger(Parse *pParse, Expr *pExpr, int negFlag, int iMem){
   }
 }
 
-#if defined(SQLITE_DEBUG)
 /*
-** Verify the consistency of the column cache
+** Erase column-cache entry number i
 */
-static int cacheIsValid(Parse *pParse){
-  int i, n;
-  for(i=n=0; i<SQLITE_N_COLCACHE; i++){
-    if( pParse->aColCache[i].iReg>0 ) n++;
-  }
-  return n==pParse->nColCache;
-}
-#endif
-
-/*
-** Clear a cache entry.
-*/
-static void cacheEntryClear(Parse *pParse, struct yColCache *p){
-  if( p->tempReg ){
+static void cacheEntryClear(Parse *pParse, int i){
+  if( pParse->aColCache[i].tempReg ){
     if( pParse->nTempReg<ArraySize(pParse->aTempReg) ){
-      pParse->aTempReg[pParse->nTempReg++] = p->iReg;
+      pParse->aTempReg[pParse->nTempReg++] = pParse->aColCache[i].iReg;
     }
-    p->tempReg = 0;
   }
-  p->iReg = 0;
   pParse->nColCache--;
-  assert( pParse->db->mallocFailed || cacheIsValid(pParse) );
+  if( i<pParse->nColCache ){
+    pParse->aColCache[i] = pParse->aColCache[pParse->nColCache];
+  }
 }
 
 
@@ -3019,46 +3006,33 @@ void sqlite3ExprCacheStore(Parse *pParse, int iTab, int iCol, int iReg){
   ** that the object will never already be in cache.  Verify this guarantee.
   */
 #ifndef NDEBUG
-  for(i=0, p=pParse->aColCache; i<SQLITE_N_COLCACHE; i++, p++){
-    assert( p->iReg==0 || p->iTable!=iTab || p->iColumn!=iCol );
+  for(i=0, p=pParse->aColCache; i<pParse->nColCache; i++, p++){
+    assert( p->iTable!=iTab || p->iColumn!=iCol );
   }
 #endif
 
-  /* Find an empty slot and replace it */
-  for(i=0, p=pParse->aColCache; i<SQLITE_N_COLCACHE; i++, p++){
-    if( p->iReg==0 ){
-      p->iLevel = pParse->iCacheLevel;
-      p->iTable = iTab;
-      p->iColumn = iCol;
-      p->iReg = iReg;
-      p->tempReg = 0;
-      p->lru = pParse->iCacheCnt++;
-      pParse->nColCache++;
-      assert( pParse->db->mallocFailed || cacheIsValid(pParse) );
-      return;
-    }
-  }
-
-  /* Replace the last recently used */
-  minLru = 0x7fffffff;
-  idxLru = -1;
-  for(i=0, p=pParse->aColCache; i<SQLITE_N_COLCACHE; i++, p++){
-    if( p->lru<minLru ){
-      idxLru = i;
-      minLru = p->lru;
+  /* If the cache is already full, delete the least recently used entry */
+  if( pParse->nColCache>=SQLITE_N_COLCACHE ){
+    minLru = 0x7fffffff;
+    idxLru = -1;
+    for(i=0, p=pParse->aColCache; i<SQLITE_N_COLCACHE; i++, p++){
+      if( p->lru<minLru ){
+        idxLru = i;
+        minLru = p->lru;
+      }
     }
-  }
-  if( ALWAYS(idxLru>=0) ){
     p = &pParse->aColCache[idxLru];
-    p->iLevel = pParse->iCacheLevel;
-    p->iTable = iTab;
-    p->iColumn = iCol;
-    p->iReg = iReg;
-    p->tempReg = 0;
-    p->lru = pParse->iCacheCnt++;
-    assert( cacheIsValid(pParse) );
-    return;
+  }else{
+    p = &pParse->aColCache[pParse->nColCache++];
   }
+
+  /* Add the new entry to the end of the cache */
+  p->iLevel = pParse->iCacheLevel;
+  p->iTable = iTab;
+  p->iColumn = iCol;
+  p->iReg = iReg;
+  p->tempReg = 0;
+  p->lru = pParse->iCacheCnt++;
 }
 
 /*
@@ -3066,13 +3040,14 @@ void sqlite3ExprCacheStore(Parse *pParse, int iTab, int iCol, int iReg){
 ** Purge the range of registers from the column cache.
 */
 void sqlite3ExprCacheRemove(Parse *pParse, int iReg, int nReg){
-  struct yColCache *p;
-  if( iReg<=0 || pParse->nColCache==0 ) return;
-  p = &pParse->aColCache[SQLITE_N_COLCACHE-1];
-  while(1){
-    if( p->iReg >= iReg && p->iReg < iReg+nReg ) cacheEntryClear(pParse, p);
-    if( p==pParse->aColCache ) break;
-    p--;
+  int i = 0;
+  while( i<pParse->nColCache ){
+    struct yColCache *p = &pParse->aColCache[i];
+    if( p->iReg >= iReg && p->iReg < iReg+nReg ){
+      cacheEntryClear(pParse, i);
+    }else{
+      i++;
+    }
   }
 }
 
@@ -3096,8 +3071,7 @@ void sqlite3ExprCachePush(Parse *pParse){
 ** the cache to the state it was in prior the most recent Push.
 */
 void sqlite3ExprCachePop(Parse *pParse){
-  int i;
-  struct yColCache *p;
+  int i = 0;
   assert( pParse->iCacheLevel>=1 );
   pParse->iCacheLevel--;
 #ifdef SQLITE_DEBUG
@@ -3105,9 +3079,11 @@ void sqlite3ExprCachePop(Parse *pParse){
     printf("POP  to %d\n", pParse->iCacheLevel);
   }
 #endif
-  for(i=0, p=pParse->aColCache; i<SQLITE_N_COLCACHE; i++, p++){
-    if( p->iReg && p->iLevel>pParse->iCacheLevel ){
-      cacheEntryClear(pParse, p);
+  while( i<pParse->nColCache ){
+    if( pParse->aColCache[i].iLevel>pParse->iCacheLevel ){
+      cacheEntryClear(pParse, i);
+    }else{
+      i++;
     }
   }
 }
@@ -3121,7 +3097,7 @@ void sqlite3ExprCachePop(Parse *pParse){
 static void sqlite3ExprCachePinRegister(Parse *pParse, int iReg){
   int i;
   struct yColCache *p;
-  for(i=0, p=pParse->aColCache; i<SQLITE_N_COLCACHE; i++, p++){
+  for(i=0, p=pParse->aColCache; i<pParse->nColCache; i++, p++){
     if( p->iReg==iReg ){
       p->tempReg = 0;
     }
@@ -3199,7 +3175,7 @@ int sqlite3ExprCodeGetColumn(
   int i;
   struct yColCache *p;
 
-  for(i=0, p=pParse->aColCache; i<SQLITE_N_COLCACHE; i++, p++){
+  for(i=0, p=pParse->aColCache; i<pParse->nColCache; i++, p++){
     if( p->iReg>0 && p->iTable==iTable && p->iColumn==iColumn ){
       p->lru = pParse->iCacheCnt++;
       sqlite3ExprCachePinRegister(pParse, p->iReg);
@@ -3232,18 +3208,20 @@ void sqlite3ExprCodeGetColumnToReg(
 */
 void sqlite3ExprCacheClear(Parse *pParse){
   int i;
-  struct yColCache *p;
 
 #if SQLITE_DEBUG
   if( pParse->db->flags & SQLITE_VdbeAddopTrace ){
     printf("CLEAR\n");
   }
 #endif
-  for(i=0, p=pParse->aColCache; i<SQLITE_N_COLCACHE; i++, p++){
-    if( p->iReg ){
-      cacheEntryClear(pParse, p);
+  for(i=0; i<pParse->nColCache; i++){
+    if( pParse->aColCache[i].tempReg
+     && pParse->nTempReg<ArraySize(pParse->aTempReg)
+    ){
+       pParse->aTempReg[pParse->nTempReg++] = pParse->aColCache[i].iReg;
     }
   }
+  pParse->nColCache = 0;
 }
 
 /*
@@ -3275,7 +3253,7 @@ void sqlite3ExprCodeMove(Parse *pParse, int iFrom, int iTo, int nReg){
 static int usedAsColumnCache(Parse *pParse, int iFrom, int iTo){
   int i;
   struct yColCache *p;
-  for(i=0, p=pParse->aColCache; i<SQLITE_N_COLCACHE; i++, p++){
+  for(i=0, p=pParse->aColCache; i<pParse->nColCache; i++, p++){
     int r = p->iReg;
     if( r>=iFrom && r<=iTo ) return 1;    /*NO_TEST*/
   }
@@ -4971,7 +4949,7 @@ void sqlite3ReleaseTempReg(Parse *pParse, int iReg){
   if( iReg && pParse->nTempReg<ArraySize(pParse->aTempReg) ){
     int i;
     struct yColCache *p;
-    for(i=0, p=pParse->aColCache; i<SQLITE_N_COLCACHE; i++, p++){
+    for(i=0, p=pParse->aColCache; i<pParse->nColCache; i++, p++){
       if( p->iReg==iReg ){
         p->tempReg = 1;
         return;