Be more aggressive about reusing subqueries that appear on the RHS of IN

operators that have been replicated due to the predicate push-down optimization.

FossilOrigin-Name: 2accf32b6e45a396503c29eecc14a103bcc7b4c313cde921b26b489704060177

src/vdbe.h

@@ -32,6 +32,19 @@ typedef struct Vdbe Vdbe;
 */
 typedef struct sqlite3_value Mem;
 typedef struct SubProgram SubProgram;
+typedef struct SubrtnSig SubrtnSig;
+
+/*
+** A signature for a reusable subroutine that materializes the RHS of
+** an IN operator.
+*/
+struct SubrtnSig {
+  int selId;          /* SELECT-id for the SELECT statement on the RHS */
+  char *zAff;         /* Affinity of the overall IN expression */
+  int iTable;         /* Ephemeral table generated by the subroutine */
+  int iAddr;          /* Subroutine entry address */
+  int regReturn;      /* Register used to hold return address */
+};
 
 /*
 ** A single instruction of the virtual machine has an opcode
@@ -60,6 +73,7 @@ struct VdbeOp {
     u32 *ai;               /* Used when p4type is P4_INTARRAY */
     SubProgram *pProgram;  /* Used when p4type is P4_SUBPROGRAM */
     Table *pTab;           /* Used when p4type is P4_TABLE */
+    SubrtnSig *pSubrtnSig; /* Used when p4type is P4_SUBRTNSIG */
 #ifdef SQLITE_ENABLE_CURSOR_HINTS
     Expr *pExpr;           /* Used when p4type is P4_EXPR */
 #endif
@@ -127,6 +141,7 @@ typedef struct VdbeOpList VdbeOpList;
 #define P4_INTARRAY   (-14) /* P4 is a vector of 32-bit integers */
 #define P4_FUNCCTX    (-15) /* P4 is a pointer to an sqlite3_context object */
 #define P4_TABLEREF   (-16) /* Like P4_TABLE, but reference counted */
+#define P4_SUBRTNSIG  (-17) /* P4 is a SubrtnSig pointer */
 
 /* Error message codes for OP_Halt */
 #define P5_ConstraintNotNull 1