Allow the planner-related functions and hook to accept the query string.

This commit adds query_string argument into the planner-related functions
and hook and allows us to pass the query string to them.

Currently there is no user of the query string passed. But the upcoming patch
for the planning counters will add the planning hook function into
pg_stat_statements and the function will need the query string. So this change
will be necessary for that patch.

Also this change is useful for some extensions that want to use the query
string in their planner hook function.

Author: Pascal Legrand, Julien Rouhaud
Reviewed-by: Yoshikazu Imai, Tom Lane, Fujii Masao
Discussion: https://postgr.es/m/CAOBaU_bU1m3_XF5qKYtSj1ua4dxd=FWDyh2SH4rSJAUUfsGmAQ@mail.gmail.com
Discussion: https://postgr.es/m/1583789487074-0.post@n3.nabble.com

src/backend/commands/copy.c

@@ -1580,7 +1580,8 @@ BeginCopy(ParseState *pstate,
 		}
 
 		/* plan the query */
-		plan = pg_plan_query(query, CURSOR_OPT_PARALLEL_OK, NULL);
+		plan = pg_plan_query(query, pstate->p_sourcetext,
+							 CURSOR_OPT_PARALLEL_OK, NULL);
 
 		/*
 		 * With row level security and a user using "COPY relation TO", we

src/backend/commands/createas.c

@@ -329,7 +329,8 @@ ExecCreateTableAs(ParseState *pstate, CreateTableAsStmt *stmt,
 		Assert(query->commandType == CMD_SELECT);
 
 		/* plan the query */
-		plan = pg_plan_query(query, CURSOR_OPT_PARALLEL_OK, params);
+		plan = pg_plan_query(query, pstate->p_sourcetext,
+							 CURSOR_OPT_PARALLEL_OK, params);
 
 		/*
 		 * Use a snapshot with an updated command ID to ensure this query sees

src/backend/commands/explain.c

@@ -376,7 +376,7 @@ ExplainOneQuery(Query *query, int cursorOptions,
 		INSTR_TIME_SET_CURRENT(planstart);
 
 		/* plan the query */
-		plan = pg_plan_query(query, cursorOptions, params);
+		plan = pg_plan_query(query, queryString, cursorOptions, params);
 
 		INSTR_TIME_SET_CURRENT(planduration);
 		INSTR_TIME_SUBTRACT(planduration, planstart);

src/backend/commands/extension.c

@@ -751,7 +751,7 @@ execute_sql_string(const char *sql)
 										   NULL,
 										   0,
 										   NULL);
-		stmt_list = pg_plan_queries(stmt_list, CURSOR_OPT_PARALLEL_OK, NULL);
+		stmt_list = pg_plan_queries(stmt_list, sql, CURSOR_OPT_PARALLEL_OK, NULL);
 
 		foreach(lc2, stmt_list)
 		{

src/backend/commands/matview.c

@@ -391,7 +391,7 @@ refresh_matview_datafill(DestReceiver *dest, Query *query,
 	CHECK_FOR_INTERRUPTS();
 
 	/* Plan the query which will generate data for the refresh. */
-	plan = pg_plan_query(query, 0, NULL);
+	plan = pg_plan_query(query, queryString, 0, NULL);
 
 	/*
 	 * Use a snapshot with an updated command ID to ensure this query sees

src/backend/commands/portalcmds.c

@@ -90,7 +90,7 @@ PerformCursorOpen(ParseState *pstate, DeclareCursorStmt *cstmt, ParamListInfo pa
 		elog(ERROR, "non-SELECT statement in DECLARE CURSOR");
 
 	/* Plan the query, applying the specified options */
-	plan = pg_plan_query(query, cstmt->options, params);
+	plan = pg_plan_query(query, pstate->p_sourcetext, cstmt->options, params);
 
 	/*
 	 * Create a portal and copy the plan and query string into its memory.