Allow WHERE terms to be pushed down into sub-queries that contain window functions, provided that the WHERE term is made up of entirely of constants and copies of expressions found in the PARTITION BY clauses of all window functions in the sub-query.

FossilOrigin-Name: dac51f303bba1a0aac7768c688b0c134deb7641062cce2071d546f2d8f241dec

src/sqliteInt.h

@@ -3204,6 +3204,7 @@ struct Select {
 #define SF_NoopOrderBy   0x0400000 /* ORDER BY is ignored for this query */
 #define SF_UpdateFrom    0x0800000 /* Statement is an UPDATE...FROM */
 #define SF_PushDown      0x1000000 /* SELECT has be modified by push-down opt */
+#define SF_MultiPart     0x2000000 /* Has multiple incompatible PARTITIONs */
 
 /*
 ** The results of a SELECT can be distributed in several ways, as defined