Here begins an experimental branch for exploring the idea of a partial index.

This check-in is able to parse a WHERE clause on a CREATE INDEX statement, but
does not actually do anythingn with that WHERE clause yet.

FossilOrigin-Name: 6794b2dcb48b3507caccfc7867fc185818cf8291

3 files changed, 15 insertions, 10 deletions

diff --git a/src/build.c b/src/build.c
index 0a3922c95..7ca2ef00c 100644
--- a/src/build.c
+++ b/src/build.c
@@ -382,6 +382,7 @@ static void freeIndex(sqlite3 *db, Index *p){
 #ifndef SQLITE_OMIT_ANALYZE
   sqlite3DeleteIndexSamples(db, p);
 #endif
+  sqlite3ExprDelete(db, p->pPartIdxWhere);
   sqlite3DbFree(db, p->zColAff);
   sqlite3DbFree(db, p);
 }
@@ -1225,7 +1226,8 @@ void sqlite3AddPrimaryKey(
 #endif
   }else{
     Index *p;
-    p = sqlite3CreateIndex(pParse, 0, 0, 0, pList, onError, 0, 0, sortOrder, 0);
+    p = sqlite3CreateIndex(pParse, 0, 0, 0, pList, onError, 0, 0,
+                           0, sortOrder, 0);
     if( p ){
       p->autoIndex = 2;
     }
@@ -2483,6 +2485,7 @@ Index *sqlite3CreateIndex(
   int onError,       /* OE_Abort, OE_Ignore, OE_Replace, or OE_None */
   Token *pStart,     /* The CREATE token that begins this statement */
   Token *pEnd,       /* The ")" that closes the CREATE INDEX statement */
+  Expr *pPIWhere,    /* WHERE clause for partial indices */
   int sortOrder,     /* Sort order of primary key when pList==NULL */
   int ifNotExist     /* Omit error if index already exists */
 ){
@@ -2699,6 +2702,8 @@ Index *sqlite3CreateIndex(
   pIndex->uniqNotNull = onError==OE_Abort;
   pIndex->autoIndex = (u8)(pName==0);
   pIndex->pSchema = db->aDb[iDb].pSchema;
+  pIndex->pPartIdxWhere = pPIWhere;
+  pPIWhere = 0;
   assert( sqlite3SchemaMutexHeld(db, iDb, 0) );
 
   /* Check to see if we should honor DESC requests on index columns
@@ -2933,10 +2938,8 @@ Index *sqlite3CreateIndex(
 
   /* Clean up before exiting */
 exit_create_index:
-  if( pIndex ){
-    sqlite3DbFree(db, pIndex->zColAff);
-    sqlite3DbFree(db, pIndex);
-  }
+  if( pIndex ) freeIndex(db, pIndex);
+  sqlite3ExprDelete(db, pPIWhere);
   sqlite3ExprListDelete(db, pList);
   sqlite3SrcListDelete(db, pTblName);
   sqlite3DbFree(db, zName);
diff --git a/src/parse.y b/src/parse.y
index d707ee0a8..6ac2c3d44 100644
--- a/src/parse.y
+++ b/src/parse.y
@@ -300,7 +300,8 @@ ccons ::= NULL onconf.
 ccons ::= NOT NULL onconf(R).    {sqlite3AddNotNull(pParse, R);}
 ccons ::= PRIMARY KEY sortorder(Z) onconf(R) autoinc(I).
                                  {sqlite3AddPrimaryKey(pParse,0,R,I,Z);}
-ccons ::= UNIQUE onconf(R).      {sqlite3CreateIndex(pParse,0,0,0,0,R,0,0,0,0);}
+ccons ::= UNIQUE onconf(R).      {sqlite3CreateIndex(pParse,0,0,0,0,R,0,
+                                                     0,0,0,0);}
 ccons ::= CHECK LP expr(X) RP.   {sqlite3AddCheckConstraint(pParse,X.pExpr);}
 ccons ::= REFERENCES nm(T) idxlist_opt(TA) refargs(R).
                                  {sqlite3CreateForeignKey(pParse,0,&T,TA,R);}
@@ -349,7 +350,7 @@ tcons ::= CONSTRAINT nm(X).      {pParse->constraintName = X;}
 tcons ::= PRIMARY KEY LP idxlist(X) autoinc(I) RP onconf(R).
                                  {sqlite3AddPrimaryKey(pParse,X,R,I,0);}
 tcons ::= UNIQUE LP idxlist(X) RP onconf(R).
-                                 {sqlite3CreateIndex(pParse,0,0,0,X,R,0,0,0,0);}
+                               {sqlite3CreateIndex(pParse,0,0,0,X,R,0,0,0,0,0);}
 tcons ::= CHECK LP expr(E) RP onconf.
                                  {sqlite3AddCheckConstraint(pParse,E.pExpr);}
 tcons ::= FOREIGN KEY LP idxlist(FA) RP
@@ -1125,10 +1126,10 @@ nexprlist(A) ::= expr(Y).
 ///////////////////////////// The CREATE INDEX command ///////////////////////
 //
 cmd ::= createkw(S) uniqueflag(U) INDEX ifnotexists(NE) nm(X) dbnm(D)
-        ON nm(Y) LP idxlist(Z) RP(E). {
+        ON nm(Y) LP idxlist(Z) RP(E) where_opt(W). {
   sqlite3CreateIndex(pParse, &X, &D, 
                      sqlite3SrcListAppend(pParse->db,0,&Y,0), Z, U,
-                      &S, &E, SQLITE_SO_ASC, NE);
+                      &S, &E, W, SQLITE_SO_ASC, NE);
 }
 
 %type uniqueflag {int}
diff --git a/src/sqliteInt.h b/src/sqliteInt.h
index 795740978..dba1e55b8 100644
--- a/src/sqliteInt.h
+++ b/src/sqliteInt.h
@@ -1538,6 +1538,7 @@ struct Index {
   Schema *pSchema;         /* Schema containing this index */
   u8 *aSortOrder;          /* for each column: True==DESC, False==ASC */
   char **azColl;           /* Array of collation sequence names for index */
+  Expr *pPartIdxWhere;     /* WHERE clause for partial indices */
   int tnum;                /* DB Page containing root of this index */
   u16 nColumn;             /* Number of columns in table used by this index */
   u8 onError;              /* OE_Abort, OE_Ignore, OE_Replace, or OE_None */
@@ -2783,7 +2784,7 @@ void sqlite3SrcListAssignCursors(Parse*, SrcList*);
 void sqlite3IdListDelete(sqlite3*, IdList*);
 void sqlite3SrcListDelete(sqlite3*, SrcList*);
 Index *sqlite3CreateIndex(Parse*,Token*,Token*,SrcList*,ExprList*,int,Token*,
-                        Token*, int, int);
+                        Token*, Expr*, int, int);
 void sqlite3DropIndex(Parse*, SrcList*, int);
 int sqlite3Select(Parse*, Select*, SelectDest*);
 Select *sqlite3SelectNew(Parse*,ExprList*,SrcList*,Expr*,ExprList*,