Fix function expression deparsing implicit/explicit coercion.

MySQL does not support explicit coercion/casting syntax, so avoid
casting like a function call, e.g. numeric(a) while deparsing.

FDW-447, Suraj Kharage, reviewed by Vaibhav Dalvi, Jeevan Ladhe, and
tested by Rajkumar Raghuwanshi.

deparse.c

@@ -1101,6 +1101,28 @@ mysql_deparse_func_expr(FuncExpr *node, deparse_expr_cxt *context)
 	bool		first;
 	ListCell   *arg;
 
+	/*
+	 * If the function call came from an implicit coercion, then just show the
+	 * first argument.
+	 */
+	if (node->funcformat == COERCE_IMPLICIT_CAST)
+	{
+		deparseExpr((Expr *) linitial(node->args), context);
+		return;
+	}
+
+	/* If the function call came from a cast, then show the first argument. */
+	if (node->funcformat == COERCE_EXPLICIT_CAST)
+	{
+		int32		coercedTypmod;
+
+		/* Get the typmod if this is a length-coercion function */
+		(void) exprIsLengthCoercion((Node *) node, &coercedTypmod);
+
+		deparseExpr((Expr *) linitial(node->args), context);
+		return;
+	}
+
 	/*
 	 * Normal function: display as proname(args).
 	 */

expected/select.out

@@ -1400,6 +1400,25 @@ SELECT c1, c2, c3 FROM f_test_tbl1 WHERE pg_catalog.timeofday() IS NOT NULL
  500 | EMP5 | SALESMAN
 (5 rows)
 
+-- FDW-447: Fix function implicit/explicit coercion.
+EXPLAIN (VERBOSE, COSTS OFF)
+SELECT * FROM f_test_tbl1 WHERE c1 = 12.2;
+                                                            QUERY PLAN                                                            
+----------------------------------------------------------------------------------------------------------------------------------
+ Foreign Scan on public.f_test_tbl1
+   Output: c1, c2, c3, c4, c5, c6, c7, c8
+   Remote query: SELECT `c1`, `c2`, `c3`, `c4`, `c5`, `c6`, `c7`, `c8` FROM `mysql_fdw_regress`.`test_tbl1` WHERE ((`c1` = 12.2))
+(3 rows)
+
+EXPLAIN (VERBOSE, COSTS OFF)
+SELECT * FROM f_test_tbl1 WHERE c1::numeric = 12.2;
+                                                            QUERY PLAN                                                            
+----------------------------------------------------------------------------------------------------------------------------------
+ Foreign Scan on public.f_test_tbl1
+   Output: c1, c2, c3, c4, c5, c6, c7, c8
+   Remote query: SELECT `c1`, `c2`, `c3`, `c4`, `c5`, `c6`, `c7`, `c8` FROM `mysql_fdw_regress`.`test_tbl1` WHERE ((`c1` = 12.2))
+(3 rows)
+
 -- Cleanup
 DROP TABLE l_test_tbl1;
 DROP TABLE l_test_tbl2;

sql/select.sql

@@ -414,6 +414,12 @@ SELECT c1, c2, c3 FROM f_test_tbl1 WHERE pg_catalog.timeofday() IS NOT NULL
 SELECT c1, c2, c3 FROM f_test_tbl1 WHERE pg_catalog.timeofday() IS NOT NULL
   ORDER BY 1 limit 5;
 
+-- FDW-447: Fix function implicit/explicit coercion.
+EXPLAIN (VERBOSE, COSTS OFF)
+SELECT * FROM f_test_tbl1 WHERE c1 = 12.2;
+EXPLAIN (VERBOSE, COSTS OFF)
+SELECT * FROM f_test_tbl1 WHERE c1::numeric = 12.2;
+
 -- Cleanup
 DROP TABLE l_test_tbl1;
 DROP TABLE l_test_tbl2;