Merge 10.3 into 10.4

mysql-test/main/derived_cond_pushdown.test

@@ -2102,6 +2102,28 @@ eval EXPLAIN FORMAT=JSON $q2;
 DROP VIEW v1,v2;
 DROP TABLE t1;
 
+--echo #
+--echo # MDEV-18383: pushdown condition with the IF structure
+--echo #             defined with Item_cond item
+--echo #
+
+CREATE TABLE t1(a INT, b INT);
+CREATE TABLE t2(c INT, d INT);
+INSERT INTO t1 VALUES (1,2),(3,4),(5,6);
+INSERT INTO t2 VALUES (1,3),(3,7),(5,1);
+
+SELECT *
+FROM t1,
+(
+  SELECT MAX(d) AS max_d,c
+  FROM t2
+  GROUP BY c
+) AS tab
+WHERE t1.a=tab.c AND
+      IF(2,t1.a=1 OR t1.b>5,1=1);
+
+DROP TABLE t1,t2;
+
 --echo # End of 10.2 tests
 
 --echo #