Remove the Expr.pColl field and compute the collating sequence as it is needed.
This fixes the test script "shared9.test", though there is still a memory leak.
And there are other problems.  Consider this a work-in-progress.

FossilOrigin-Name: fd011cb22f2d899d94ec7ce22641d7a8f5e19972
diff --git a/src/build.c b/src/build.c
index 4c45a92..c03e502 100644
--- a/src/build.c
+++ b/src/build.c
@@ -2690,10 +2690,8 @@
   for(i=0; i<pList->nExpr; i++){
     Expr *pExpr = pList->a[i].pExpr;
     if( pExpr ){
-      CollSeq *pColl = pExpr->pColl;
-      /* Either pColl!=0 or there was an OOM failure.  But if an OOM
-      ** failure we have quit before reaching this point. */
-      if( ALWAYS(pColl) ){
+      CollSeq *pColl = sqlite3ExprCollSeq(pParse, pExpr);
+      if( pColl ){
         nExtra += (1 + sqlite3Strlen30(pColl->zName));
       }
     }
@@ -2756,6 +2754,7 @@
     const char *zColName = pListItem->zName;
     Column *pTabCol;
     int requestedSortOrder;
+    CollSeq *pColl;                /* Collating sequence */
     char *zColl;                   /* Collation sequence name */
 
     for(j=0, pTabCol=pTab->aCol; j<pTab->nCol; j++, pTabCol++){
@@ -2768,14 +2767,11 @@
       goto exit_create_index;
     }
     pIndex->aiColumn[i] = j;
-    /* Justification of the ALWAYS(pListItem->pExpr->pColl):  Because of
-    ** the way the "idxlist" non-terminal is constructed by the parser,
-    ** if pListItem->pExpr is not null then either pListItem->pExpr->pColl
-    ** must exist or else there must have been an OOM error.  But if there
-    ** was an OOM error, we would never reach this point. */
-    if( pListItem->pExpr && ALWAYS(pListItem->pExpr->pColl) ){
+    if( pListItem->pExpr
+     && (pColl = sqlite3ExprCollSeq(pParse, pListItem->pExpr))!=0
+    ){
       int nColl;
-      zColl = pListItem->pExpr->pColl->zName;
+      zColl = pColl->zName;
       nColl = sqlite3Strlen30(zColl) + 1;
       assert( nExtra>=nColl );
       memcpy(zExtra, zColl, nColl);
diff --git a/src/expr.c b/src/expr.c
index ae82848..11feaa2 100644
--- a/src/expr.c
+++ b/src/expr.c
@@ -56,66 +56,72 @@
 }
 
 /*
-** Set the explicit collating sequence for an expression to the
-** collating sequence supplied in the second argument.
-*/
-Expr *sqlite3ExprSetColl(Expr *pExpr, CollSeq *pColl){
-  if( pExpr && pColl ){
-    pExpr->pColl = pColl;
-    pExpr->flags |= EP_ExpCollate;
-  }
-  return pExpr;
-}
-
-/*
 ** Set the collating sequence for expression pExpr to be the collating
-** sequence named by pToken.   Return a pointer to the revised expression.
-** The collating sequence is marked as "explicit" using the EP_ExpCollate
-** flag.  An explicit collating sequence will override implicit
-** collating sequences.
+** sequence named by pToken.   Return a pointer to a new Expr node that
+** implements the COLLATE operator.
 */
 Expr *sqlite3ExprSetCollByToken(Parse *pParse, Expr *pExpr, Token *pCollName){
-  char *zColl = 0;            /* Dequoted name of collation sequence */
-  CollSeq *pColl;
-  sqlite3 *db = pParse->db;
-  zColl = sqlite3NameFromToken(db, pCollName);
-  pColl = sqlite3LocateCollSeq(pParse, zColl);
-  sqlite3ExprSetColl(pExpr, pColl);
-  sqlite3DbFree(db, zColl);
-  return pExpr;
+  Expr *pNew = sqlite3ExprAlloc(pParse->db, TK_COLLATE, pCollName, 1);
+  if( pNew ){
+    pNew->pLeft = pExpr;
+    pNew->flags |= EP_Collate;
+  }
+  return pNew;
 }
 
 /*
-** Return the default collation sequence for the expression pExpr. If
-** there is no default collation type, return 0.
+** Return the collation sequence for the expression pExpr. If
+** there is no defined collating sequence, return NULL.
+**
+** The collating sequence might be determined by a COLLATE operator
+** or by the presence of a column with a defined collating sequence.
+** COLLATE operators take first precedence.  Left operands take
+** precedence over right operands.
 */
 CollSeq *sqlite3ExprCollSeq(Parse *pParse, Expr *pExpr){
+  sqlite3 *db = pParse->db;
   CollSeq *pColl = 0;
   Expr *p = pExpr;
-  while( p ){
-    int op;
-    pColl = p->pColl;
-    if( pColl ) break;
-    op = p->op;
-    if( p->pTab!=0 && (
-        op==TK_AGG_COLUMN || op==TK_COLUMN || op==TK_REGISTER || op==TK_TRIGGER
-    )){
+  while( p && pColl==0 ){
+    int op = p->op;
+    if( op==TK_CAST || op==TK_UPLUS ){
+      p = p->pLeft;
+      continue;
+    }
+    if( op==TK_COLLATE ){
+      pColl = sqlite3FindCollSeq(db, ENC(db), p->u.zToken, 0);
+      break;
+    }
+    if( p->pTab!=0
+     && (op==TK_AGG_COLUMN || op==TK_COLUMN
+          || op==TK_REGISTER || op==TK_TRIGGER)
+    ){
       /* op==TK_REGISTER && p->pTab!=0 happens when pExpr was originally
       ** a TK_COLUMN but was previously evaluated and cached in a register */
-      const char *zColl;
       int j = p->iColumn;
       if( j>=0 ){
-        sqlite3 *db = pParse->db;
-        zColl = p->pTab->aCol[j].zColl;
+        const char *zColl = p->pTab->aCol[j].zColl;
         pColl = sqlite3FindCollSeq(db, ENC(db), zColl, 0);
-        pExpr->pColl = pColl;
       }
       break;
     }
-    if( op!=TK_CAST && op!=TK_UPLUS ){
+    if( p->flags & EP_Collate ){
+      if( p->pLeft->flags & EP_Collate ){
+        p = p->pLeft;
+      }else{
+        p = p->pRight;
+      }
+    }else{
       break;
     }
-    p = p->pLeft;
+#if 0
+    else if( p->flags & EP_TokenOnly ){
+      break;
+    }else{
+      pColl = sqlite3ExprCollSeq(pParse, p->pLeft);
+      p = p->pRight;
+    }
+#endif
   }
   if( sqlite3CheckCollSeq(pParse, pColl) ){ 
     pColl = 0;
@@ -219,12 +225,10 @@
 ){
   CollSeq *pColl;
   assert( pLeft );
-  if( pLeft->flags & EP_ExpCollate ){
-    assert( pLeft->pColl );
-    pColl = pLeft->pColl;
-  }else if( pRight && pRight->flags & EP_ExpCollate ){
-    assert( pRight->pColl );
-    pColl = pRight->pColl;
+  if( pLeft->flags & EP_Collate ){
+    pColl = sqlite3ExprCollSeq(pParse, pLeft);
+  }else if( pRight && (pRight->flags & EP_Collate)!=0 ){
+    pColl = sqlite3ExprCollSeq(pParse, pRight);
   }else{
     pColl = sqlite3ExprCollSeq(pParse, pLeft);
     if( !pColl ){
@@ -454,17 +458,11 @@
   }else{
     if( pRight ){
       pRoot->pRight = pRight;
-      if( pRight->flags & EP_ExpCollate ){
-        pRoot->flags |= EP_ExpCollate;
-        pRoot->pColl = pRight->pColl;
-      }
+      pRoot->flags |= EP_Collate & pRight->flags;
     }
     if( pLeft ){
       pRoot->pLeft = pLeft;
-      if( pLeft->flags & EP_ExpCollate ){
-        pRoot->flags |= EP_ExpCollate;
-        pRoot->pColl = pLeft->pColl;
-      }
+      pRoot->flags |= EP_Collate & pLeft->flags;
     }
     exprSetHeight(pRoot);
   }
@@ -722,7 +720,7 @@
     assert( !ExprHasProperty(p, EP_FromJoin) ); 
     assert( (p->flags2 & EP2_MallocedToken)==0 );
     assert( (p->flags2 & EP2_Irreducible)==0 );
-    if( p->pLeft || p->pRight || p->pColl || p->x.pList ){
+    if( p->pLeft || p->pRight || p->x.pList ){
       nSize = EXPR_REDUCEDSIZE | EP_Reduced;
     }else{
       nSize = EXPR_TOKENONLYSIZE | EP_TokenOnly;
@@ -2746,6 +2744,7 @@
       sqlite3ReleaseTempReg(pParse, r4);
       break;
     }
+    case TK_COLLATE: 
     case TK_UPLUS: {
       inReg = sqlite3ExprCodeTarget(pParse, pExpr->pLeft, target);
       break;
@@ -3773,7 +3772,15 @@
     return 2;
   }
   if( (pA->flags & EP_Distinct)!=(pB->flags & EP_Distinct) ) return 2;
-  if( pA->op!=pB->op ) return 2;
+  if( pA->op!=pB->op ){
+    if( pA->op==TK_COLLATE && sqlite3ExprCompare(pA->pLeft, pB)<2 ){
+      return 1;
+    }
+    if( pB->op==TK_COLLATE && sqlite3ExprCompare(pA, pB->pLeft)<2 ){
+      return 1;
+    }
+    return 2;
+  }
   if( sqlite3ExprCompare(pA->pLeft, pB->pLeft) ) return 2;
   if( sqlite3ExprCompare(pA->pRight, pB->pRight) ) return 2;
   if( sqlite3ExprListCompare(pA->x.pList, pB->x.pList) ) return 2;
@@ -3785,11 +3792,9 @@
   }else if( pA->op!=TK_COLUMN && ALWAYS(pA->op!=TK_AGG_COLUMN) && pA->u.zToken){
     if( ExprHasProperty(pB, EP_IntValue) || NEVER(pB->u.zToken==0) ) return 2;
     if( strcmp(pA->u.zToken,pB->u.zToken)!=0 ){
-      return 2;
+      return pA->op==TK_COLLATE ? 1 : 2;
     }
   }
-  if( (pA->flags & EP_ExpCollate)!=(pB->flags & EP_ExpCollate) ) return 1;
-  if( (pA->flags & EP_ExpCollate)!=0 && pA->pColl!=pB->pColl ) return 2;
   return 0;
 }
 
diff --git a/src/fkey.c b/src/fkey.c
index a3214a9..a120b7b 100644
--- a/src/fkey.c
+++ b/src/fkey.c
@@ -516,7 +516,7 @@
         if( pTab->iPKey==iCol ) iCol = -1;
         pLeft->iTable = regData+iCol+1;
         pLeft->affinity = pCol->affinity;
-        pLeft->pColl = sqlite3LocateCollSeq(pParse, pCol->zColl);
+        // fix me.  pLeft->pColl = sqlite3LocateCollSeq(pParse, pCol->zColl);
       }else{
         pLeft->iTable = regData;
         pLeft->affinity = SQLITE_AFF_INTEGER;
diff --git a/src/resolve.c b/src/resolve.c
index 0ffc633..c2b0523 100644
--- a/src/resolve.c
+++ b/src/resolve.c
@@ -114,10 +114,6 @@
     pDup->flags2 |= EP2_MallocedToken;
     pDup->u.zToken = sqlite3DbStrDup(db, zToken);
   }
-  if( pExpr->flags & EP_ExpCollate ){
-    pDup->pColl = pExpr->pColl;
-    pDup->flags |= EP_ExpCollate;
-  }
 
   /* Before calling sqlite3ExprDelete(), set the EP_Static flag. This 
   ** prevents ExprDelete() from deleting the Expr structure itself,
@@ -830,13 +826,10 @@
         }
       }
       if( iCol>0 ){
-        CollSeq *pColl = pE->pColl;
-        int flags = pE->flags & EP_ExpCollate;
         sqlite3ExprDelete(db, pE);
         pItem->pExpr = pE = sqlite3Expr(db, TK_INTEGER, 0);
         if( pE==0 ) return 1;
-        pE->pColl = pColl;
-        pE->flags |= EP_IntValue | flags;
+        pE->flags |= EP_IntValue;
         pE->u.iValue = iCol;
         pItem->iOrderByCol = (u16)iCol;
         pItem->done = 1;
diff --git a/src/select.c b/src/select.c
index cba766f..ee1755d 100644
--- a/src/select.c
+++ b/src/select.c
@@ -2333,12 +2333,10 @@
       for(i=0; i<nOrderBy; i++){
         CollSeq *pColl;
         Expr *pTerm = pOrderBy->a[i].pExpr;
-        if( pTerm->flags & EP_ExpCollate ){
-          pColl = pTerm->pColl;
+        if( pTerm->flags & EP_Collate ){
+          pColl = sqlite3ExprCollSeq(pParse, pTerm);
         }else{
           pColl = multiSelectCollSeq(pParse, p, aPermute[i]);
-          pTerm->flags |= EP_ExpCollate;
-          pTerm->pColl = pColl;
         }
         pKeyMerge->aColl[i] = pColl;
         pKeyMerge->aSortOrder[i] = pOrderBy->a[i].sortOrder;
@@ -2608,9 +2606,6 @@
       assert( pEList!=0 && pExpr->iColumn<pEList->nExpr );
       assert( pExpr->pLeft==0 && pExpr->pRight==0 );
       pNew = sqlite3ExprDup(db, pEList->a[pExpr->iColumn].pExpr, 0);
-      if( pNew && pExpr->pColl ){
-        pNew->pColl = pExpr->pColl;
-      }
       sqlite3ExprDelete(db, pExpr);
       pExpr = pNew;
     }
diff --git a/src/sqliteInt.h b/src/sqliteInt.h
index b9b9e6c..fc975bd 100644
--- a/src/sqliteInt.h
+++ b/src/sqliteInt.h
@@ -1678,7 +1678,6 @@
     ExprList *pList;     /* Function arguments or in "<expr> IN (<expr-list)" */
     Select *pSelect;     /* Used for sub-selects and "<expr> IN (<select>)" */
   } x;
-  CollSeq *pColl;        /* The collation type of the column or 0 */
 
   /* If the EP_Reduced flag is set in the Expr.flags mask, then no
   ** space is allocated for the fields below this point. An attempt to
@@ -1714,7 +1713,7 @@
 #define EP_VarSelect  0x0020  /* pSelect is correlated, not constant */
 #define EP_DblQuoted  0x0040  /* token.z was originally in "..." */
 #define EP_InfixFunc  0x0080  /* True for an infix function: LIKE, GLOB, etc */
-#define EP_ExpCollate 0x0100  /* Collating sequence specified explicitly */
+#define EP_Collate    0x0100  /* Tree contains a TK_COLLATE opeartor */
 #define EP_FixedDest  0x0200  /* Result needed in a specific register */
 #define EP_IntValue   0x0400  /* Integer value contained in u.iValue */
 #define EP_xIsSelect  0x0800  /* x.pSelect is valid (otherwise x.pList is) */
@@ -3022,7 +3021,6 @@
 CollSeq *sqlite3FindCollSeq(sqlite3*,u8 enc, const char*,int);
 CollSeq *sqlite3LocateCollSeq(Parse *pParse, const char*zName);
 CollSeq *sqlite3ExprCollSeq(Parse *pParse, Expr *pExpr);
-Expr *sqlite3ExprSetColl(Expr*, CollSeq*);
 Expr *sqlite3ExprSetCollByToken(Parse *pParse, Expr*, Token*);
 int sqlite3CheckCollSeq(Parse *, CollSeq *);
 int sqlite3CheckObjectName(Parse *, const char *);
diff --git a/src/where.c b/src/where.c
index 196d8f5..02fb722 100644
--- a/src/where.c
+++ b/src/where.c
@@ -563,23 +563,32 @@
 ** Commute a comparison operator.  Expressions of the form "X op Y"
 ** are converted into "Y op X".
 **
-** If a collation sequence is associated with either the left or right
+** If left/right precendence rules come into play when determining the
+** collating
 ** side of the comparison, it remains associated with the same side after
 ** the commutation. So "Y collate NOCASE op X" becomes 
-** "X collate NOCASE op Y". This is because any collation sequence on
+** "X op Y". This is because any collation sequence on
 ** the left hand side of a comparison overrides any collation sequence 
-** attached to the right. For the same reason the EP_ExpCollate flag
+** attached to the right. For the same reason the EP_Collate flag
 ** is not commuted.
 */
 static void exprCommute(Parse *pParse, Expr *pExpr){
-  u16 expRight = (pExpr->pRight->flags & EP_ExpCollate);
-  u16 expLeft = (pExpr->pLeft->flags & EP_ExpCollate);
+  u16 expRight = (pExpr->pRight->flags & EP_Collate);
+  u16 expLeft = (pExpr->pLeft->flags & EP_Collate);
   assert( allowedOp(pExpr->op) && pExpr->op!=TK_IN );
-  pExpr->pRight->pColl = sqlite3ExprCollSeq(pParse, pExpr->pRight);
-  pExpr->pLeft->pColl = sqlite3ExprCollSeq(pParse, pExpr->pLeft);
-  SWAP(CollSeq*,pExpr->pRight->pColl,pExpr->pLeft->pColl);
-  pExpr->pRight->flags = (pExpr->pRight->flags & ~EP_ExpCollate) | expLeft;
-  pExpr->pLeft->flags = (pExpr->pLeft->flags & ~EP_ExpCollate) | expRight;
+  if( expRight==expLeft ){
+    /* Either X and Y both have COLLATE operator or neither do */
+    if( expRight ){
+      /* Both X and Y have COLLATE operators.  Make sure X is always
+      ** used by clearing the EP_Collate flag from Y. */
+      pExpr->pRight->flags &= ~EP_Collate;
+    }else if( sqlite3ExprCollSeq(pParse, pExpr->pLeft)!=0 ){
+      /* Neither X nor Y have COLLATE operators, but X has a non-default
+      ** collating sequence.  So add the EP_Collate marker on X to cause
+      ** it to be searched first. */
+      pExpr->pLeft->flags |= EP_Collate;
+    }
+  }
   SWAP(Expr*,pExpr->pRight,pExpr->pLeft);
   if( pExpr->op>=TK_GT ){
     assert( TK_LT==TK_GT+2 );
@@ -1314,7 +1323,7 @@
     Expr *pNewExpr2;
     int idxNew1;
     int idxNew2;
-    CollSeq *pColl;    /* Collating sequence to use */
+    Token sCollSeqName;  /* Name of collating sequence */
 
     pLeft = pExpr->x.pList->a[1].pExpr;
     pStr2 = sqlite3ExprDup(db, pStr1, 0);
@@ -1336,16 +1345,19 @@
       }
       *pC = c + 1;
     }
-    pColl = sqlite3FindCollSeq(db, SQLITE_UTF8, noCase ? "NOCASE" : "BINARY",0);
+    sCollSeqName.z = noCase ? "NOCASE" : "BINARY";
+    sCollSeqName.n = 6;
+    pNewExpr1 = sqlite3ExprDup(db, pLeft, 0);
     pNewExpr1 = sqlite3PExpr(pParse, TK_GE, 
-                     sqlite3ExprSetColl(sqlite3ExprDup(db,pLeft,0), pColl),
-                     pStr1, 0);
+           sqlite3ExprSetCollByToken(pParse,pNewExpr1,&sCollSeqName),
+           pStr1, 0);
     idxNew1 = whereClauseInsert(pWC, pNewExpr1, TERM_VIRTUAL|TERM_DYNAMIC);
     testcase( idxNew1==0 );
     exprAnalyze(pSrc, pWC, idxNew1);
+    pNewExpr2 = sqlite3ExprDup(db, pLeft, 0);
     pNewExpr2 = sqlite3PExpr(pParse, TK_LT,
-                     sqlite3ExprSetColl(sqlite3ExprDup(db,pLeft,0), pColl),
-                     pStr2, 0);
+           sqlite3ExprSetCollByToken(pParse,pNewExpr2,&sCollSeqName),
+           pStr2, 0);
     idxNew2 = whereClauseInsert(pWC, pNewExpr2, TERM_VIRTUAL|TERM_DYNAMIC);
     testcase( idxNew2==0 );
     exprAnalyze(pSrc, pWC, idxNew2);