Start of experimental implementation of SQL window functions. Does not yet

work.

FossilOrigin-Name: 3781e520854808fe02ad3fe77dd11fc917448c58ff1fd79123289dd91937decd

src/window.c

@@ -0,0 +1,53 @@
+/*
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+*/
+#include "sqliteInt.h"
+
+void sqlite3WindowDelete(sqlite3 *db, Window *p){
+  if( p ){
+    sqlite3ExprDelete(db, p->pFilter);
+    sqlite3ExprListDelete(db, p->pPartition);
+    sqlite3ExprListDelete(db, p->pOrderBy);
+    sqlite3ExprDelete(db, p->pEnd);
+    sqlite3ExprDelete(db, p->pStart);
+    sqlite3DbFree(db, p);
+  }
+}
+
+Window *sqlite3WindowAlloc(
+  Parse *pParse, 
+  int eType,
+  int eEnd, Expr *pEnd, 
+  int eStart, Expr *pStart
+){
+  Window *pWin = (Window*)sqlite3DbMallocZero(pParse->db, sizeof(Window));
+
+  if( pWin ){
+    pWin->eType = eType;
+    pWin->eStart = eStart;
+    pWin->eEnd = eEnd;
+    pWin->pEnd = pEnd;
+    pWin->pStart = pStart;
+  }else{
+    sqlite3ExprDelete(pParse->db, pEnd);
+    sqlite3ExprDelete(pParse->db, pStart);
+  }
+
+  return pWin;
+}
+
+void sqlite3WindowAttach(Parse *pParse, Expr *p, Window *pWin){
+  if( p ){
+    p->pWin = pWin;
+  }else{
+    sqlite3WindowDelete(pParse->db, pWin);
+  }
+}