Refactor PgFdwModifyState creation/destruction into separate functions.

Etsuro Fujita.  The larger patch series of which this is a part has
been reviewed by Amit Langote, David Fetter, Maksim Milyutin,
Álvaro Herrera, Stephen Frost, and me.

Discussion: http://postgr.es/m/5A95487E.9050808@lab.ntt.co.jp

Author: robertmhaas

contrib/postgres_fdw/postgres_fdw.c

@@ -376,12 +376,21 @@ static bool ec_member_matches_foreign(PlannerInfo *root, RelOptInfo *rel,
 static void create_cursor(ForeignScanState *node);
 static void fetch_more_data(ForeignScanState *node);
 static void close_cursor(PGconn *conn, unsigned int cursor_number);
+static PgFdwModifyState *create_foreign_modify(EState *estate,
+					  ResultRelInfo *resultRelInfo,
+					  CmdType operation,
+					  Plan *subplan,
+					  char *query,
+					  List *target_attrs,
+					  bool has_returning,
+					  List *retrieved_attrs);
 static void prepare_foreign_modify(PgFdwModifyState *fmstate);
 static const char **convert_prep_stmt_params(PgFdwModifyState *fmstate,
 						 ItemPointer tupleid,
 						 TupleTableSlot *slot);
 static void store_returning_result(PgFdwModifyState *fmstate,
 					   TupleTableSlot *slot, PGresult *res);
+static void finish_foreign_modify(PgFdwModifyState *fmstate);
 static List *build_remote_returning(Index rtindex, Relation rel,
 					   List *returningList);
 static void rebuild_fdw_scan_tlist(ForeignScan *fscan, List *tlist);
@@ -1681,18 +1690,10 @@ postgresBeginForeignModify(ModifyTableState *mtstate,
 						   int eflags)
 {
 	PgFdwModifyState *fmstate;
-	EState	   *estate = mtstate->ps.state;
-	CmdType		operation = mtstate->operation;
-	Relation	rel = resultRelInfo->ri_RelationDesc;
-	RangeTblEntry *rte;
-	Oid			userid;
-	ForeignTable *table;
-	UserMapping *user;
-	AttrNumber	n_params;
-	Oid			typefnoid;
-	bool		isvarlena;
-	ListCell   *lc;
-	TupleDesc	tupdesc = RelationGetDescr(rel);
+	char	   *query;
+	List	   *target_attrs;
+	bool		has_returning;
+	List	   *retrieved_attrs;
 
 	/*
 	 * Do nothing in EXPLAIN (no ANALYZE) case.  resultRelInfo->ri_FdwState
@@ -1701,82 +1702,25 @@ postgresBeginForeignModify(ModifyTableState *mtstate,
 	if (eflags & EXEC_FLAG_EXPLAIN_ONLY)
 		return;
 
-	/* Begin constructing PgFdwModifyState. */
-	fmstate = (PgFdwModifyState *) palloc0(sizeof(PgFdwModifyState));
-	fmstate->rel = rel;
-
-	/*
-	 * Identify which user to do the remote access as.  This should match what
-	 * ExecCheckRTEPerms() does.
-	 */
-	rte = rt_fetch(resultRelInfo->ri_RangeTableIndex, estate->es_range_table);
-	userid = rte->checkAsUser ? rte->checkAsUser : GetUserId();
-
-	/* Get info about foreign table. */
-	table = GetForeignTable(RelationGetRelid(rel));
-	user = GetUserMapping(userid, table->serverid);
-
-	/* Open connection; report that we'll create a prepared statement. */
-	fmstate->conn = GetConnection(user, true);
-	fmstate->p_name = NULL;		/* prepared statement not made yet */
-
 	/* Deconstruct fdw_private data. */
-	fmstate->query = strVal(list_nth(fdw_private,
-									 FdwModifyPrivateUpdateSql));
-	fmstate->target_attrs = (List *) list_nth(fdw_private,
-											  FdwModifyPrivateTargetAttnums);
-	fmstate->has_returning = intVal(list_nth(fdw_private,
-											 FdwModifyPrivateHasReturning));
-	fmstate->retrieved_attrs = (List *) list_nth(fdw_private,
-												 FdwModifyPrivateRetrievedAttrs);
-
-	/* Create context for per-tuple temp workspace. */
-	fmstate->temp_cxt = AllocSetContextCreate(estate->es_query_cxt,
-											  "postgres_fdw temporary data",
-											  ALLOCSET_SMALL_SIZES);
-
-	/* Prepare for input conversion of RETURNING results. */
-	if (fmstate->has_returning)
-		fmstate->attinmeta = TupleDescGetAttInMetadata(tupdesc);
-
-	/* Prepare for output conversion of parameters used in prepared stmt. */
-	n_params = list_length(fmstate->target_attrs) + 1;
-	fmstate->p_flinfo = (FmgrInfo *) palloc0(sizeof(FmgrInfo) * n_params);
-	fmstate->p_nums = 0;
-
-	if (operation == CMD_UPDATE || operation == CMD_DELETE)
-	{
-		/* Find the ctid resjunk column in the subplan's result */
-		Plan	   *subplan = mtstate->mt_plans[subplan_index]->plan;
-
-		fmstate->ctidAttno = ExecFindJunkAttributeInTlist(subplan->targetlist,
-														  "ctid");
-		if (!AttributeNumberIsValid(fmstate->ctidAttno))
-			elog(ERROR, "could not find junk ctid column");
-
-		/* First transmittable parameter will be ctid */
-		getTypeOutputInfo(TIDOID, &typefnoid, &isvarlena);
-		fmgr_info(typefnoid, &fmstate->p_flinfo[fmstate->p_nums]);
-		fmstate->p_nums++;
-	}
-
-	if (operation == CMD_INSERT || operation == CMD_UPDATE)
-	{
-		/* Set up for remaining transmittable parameters */
-		foreach(lc, fmstate->target_attrs)
-		{
-			int			attnum = lfirst_int(lc);
-			Form_pg_attribute attr = TupleDescAttr(tupdesc, attnum - 1);
-
-			Assert(!attr->attisdropped);
-
-			getTypeOutputInfo(attr->atttypid, &typefnoid, &isvarlena);
-			fmgr_info(typefnoid, &fmstate->p_flinfo[fmstate->p_nums]);
-			fmstate->p_nums++;
-		}
-	}
-
-	Assert(fmstate->p_nums <= n_params);
+	query = strVal(list_nth(fdw_private,
+							FdwModifyPrivateUpdateSql));
+	target_attrs = (List *) list_nth(fdw_private,
+									 FdwModifyPrivateTargetAttnums);
+	has_returning = intVal(list_nth(fdw_private,
+									FdwModifyPrivateHasReturning));
+	retrieved_attrs = (List *) list_nth(fdw_private,
+										FdwModifyPrivateRetrievedAttrs);
+
+	/* Construct an execution state. */
+	fmstate = create_foreign_modify(mtstate->ps.state,
+									resultRelInfo,
+									mtstate->operation,
+									mtstate->mt_plans[subplan_index]->plan,
+									query,
+									target_attrs,
+									has_returning,
+									retrieved_attrs);
 
 	resultRelInfo->ri_FdwState = fmstate;
 }
@@ -2011,28 +1955,8 @@ postgresEndForeignModify(EState *estate,
 	if (fmstate == NULL)
 		return;
 
-	/* If we created a prepared statement, destroy it */
-	if (fmstate->p_name)
-	{
-		char		sql[64];
-		PGresult   *res;
-
-		snprintf(sql, sizeof(sql), "DEALLOCATE %s", fmstate->p_name);
-
-		/*
-		 * We don't use a PG_TRY block here, so be careful not to throw error
-		 * without releasing the PGresult.
-		 */
-		res = pgfdw_exec_query(fmstate->conn, sql);
-		if (PQresultStatus(res) != PGRES_COMMAND_OK)
-			pgfdw_report_error(ERROR, res, fmstate->conn, true, sql);
-		PQclear(res);
-		fmstate->p_name = NULL;
-	}
-
-	/* Release remote connection */
-	ReleaseConnection(fmstate->conn);
-	fmstate->conn = NULL;
+	/* Destroy the execution state */
+	finish_foreign_modify(fmstate);
 }
 
 /*
@@ -3228,6 +3152,109 @@ close_cursor(PGconn *conn, unsigned int cursor_number)
 	PQclear(res);
 }
 
+/*
+ * create_foreign_modify
+ *		Construct an execution state of a foreign insert/update/delete
+ *		operation
+ */
+static PgFdwModifyState *
+create_foreign_modify(EState *estate,
+					  ResultRelInfo *resultRelInfo,
+					  CmdType operation,
+					  Plan *subplan,
+					  char *query,
+					  List *target_attrs,
+					  bool has_returning,
+					  List *retrieved_attrs)
+{
+	PgFdwModifyState *fmstate;
+	Relation	rel = resultRelInfo->ri_RelationDesc;
+	TupleDesc	tupdesc = RelationGetDescr(rel);
+	RangeTblEntry *rte;
+	Oid			userid;
+	ForeignTable *table;
+	UserMapping *user;
+	AttrNumber	n_params;
+	Oid			typefnoid;
+	bool		isvarlena;
+	ListCell   *lc;
+
+	/* Begin constructing PgFdwModifyState. */
+	fmstate = (PgFdwModifyState *) palloc0(sizeof(PgFdwModifyState));
+	fmstate->rel = rel;
+
+	/*
+	 * Identify which user to do the remote access as.  This should match what
+	 * ExecCheckRTEPerms() does.
+	 */
+	rte = rt_fetch(resultRelInfo->ri_RangeTableIndex, estate->es_range_table);
+	userid = rte->checkAsUser ? rte->checkAsUser : GetUserId();
+
+	/* Get info about foreign table. */
+	table = GetForeignTable(RelationGetRelid(rel));
+	user = GetUserMapping(userid, table->serverid);
+
+	/* Open connection; report that we'll create a prepared statement. */
+	fmstate->conn = GetConnection(user, true);
+	fmstate->p_name = NULL;		/* prepared statement not made yet */
+
+	/* Set up remote query information. */
+	fmstate->query = query;
+	fmstate->target_attrs = target_attrs;
+	fmstate->has_returning = has_returning;
+	fmstate->retrieved_attrs = retrieved_attrs;
+
+	/* Create context for per-tuple temp workspace. */
+	fmstate->temp_cxt = AllocSetContextCreate(estate->es_query_cxt,
+											  "postgres_fdw temporary data",
+											  ALLOCSET_SMALL_SIZES);
+
+	/* Prepare for input conversion of RETURNING results. */
+	if (fmstate->has_returning)
+		fmstate->attinmeta = TupleDescGetAttInMetadata(tupdesc);
+
+	/* Prepare for output conversion of parameters used in prepared stmt. */
+	n_params = list_length(fmstate->target_attrs) + 1;
+	fmstate->p_flinfo = (FmgrInfo *) palloc0(sizeof(FmgrInfo) * n_params);
+	fmstate->p_nums = 0;
+
+	if (operation == CMD_UPDATE || operation == CMD_DELETE)
+	{
+		Assert(subplan != NULL);
+
+		/* Find the ctid resjunk column in the subplan's result */
+		fmstate->ctidAttno = ExecFindJunkAttributeInTlist(subplan->targetlist,
+														  "ctid");
+		if (!AttributeNumberIsValid(fmstate->ctidAttno))
+			elog(ERROR, "could not find junk ctid column");
+
+		/* First transmittable parameter will be ctid */
+		getTypeOutputInfo(TIDOID, &typefnoid, &isvarlena);
+		fmgr_info(typefnoid, &fmstate->p_flinfo[fmstate->p_nums]);
+		fmstate->p_nums++;
+	}
+
+	if (operation == CMD_INSERT || operation == CMD_UPDATE)
+	{
+		/* Set up for remaining transmittable parameters */
+		foreach(lc, fmstate->target_attrs)
+		{
+			int			attnum = lfirst_int(lc);
+			Form_pg_attribute attr = TupleDescAttr(tupdesc, attnum - 1);
+
+			Assert(!attr->attisdropped);
+
+			getTypeOutputInfo(attr->atttypid, &typefnoid, &isvarlena);
+			fmgr_info(typefnoid, &fmstate->p_flinfo[fmstate->p_nums]);
+			fmstate->p_nums++;
+		}
+	}
+
+	Assert(fmstate->p_nums <= n_params);
+
+	return fmstate;
+}
+
 /*
  * prepare_foreign_modify
  *		Establish a prepared statement for execution of INSERT/UPDATE/DELETE
@@ -3370,6 +3397,39 @@ store_returning_result(PgFdwModifyState *fmstate,
 	PG_END_TRY();
 }
 
+/*
+ * finish_foreign_modify
+ *		Release resources for a foreign insert/update/delete operation
+ */
+static void
+finish_foreign_modify(PgFdwModifyState *fmstate)
+{
+	Assert(fmstate != NULL);
+
+	/* If we created a prepared statement, destroy it */
+	if (fmstate->p_name)
+	{
+		char		sql[64];
+		PGresult   *res;
+
+		snprintf(sql, sizeof(sql), "DEALLOCATE %s", fmstate->p_name);
+
+		/*
+		 * We don't use a PG_TRY block here, so be careful not to throw error
+		 * without releasing the PGresult.
+		 */
+		res = pgfdw_exec_query(fmstate->conn, sql);
+		if (PQresultStatus(res) != PGRES_COMMAND_OK)
+			pgfdw_report_error(ERROR, res, fmstate->conn, true, sql);
+		PQclear(res);
+		fmstate->p_name = NULL;
+	}
+
+	/* Release remote connection */
+	ReleaseConnection(fmstate->conn);
+	fmstate->conn = NULL;
+}
+
 /*
  * build_remote_returning
  *		Build a RETURNING targetlist of a remote query for performing an