expression: Granular Control in mysql.expr_pushdown_blacklist Configu…

…ration (pingcap#49324)

close pingcap#49126

pkg/expression/expression.go

@@ -1331,7 +1331,9 @@ func canFuncBePushed(sf *ScalarFunction, storeType kv.StoreType) bool {
 	}
 
 	if ret {
-		ret = IsPushDownEnabled(sf.FuncName.L, storeType)
+		funcFullName := fmt.Sprintf("%s.%s", sf.FuncName.L, strings.ToLower(sf.Function.PbCode().String()))
+		// Aside from checking function name, also check the pb name in case only the specific push down is disabled.
+		ret = IsPushDownEnabled(sf.FuncName.L, storeType) && IsPushDownEnabled(funcFullName, storeType)
 	}
 	return ret
 }

pkg/expression/integration_test/integration_test.go

@@ -673,7 +673,8 @@ func TestExprPushdownBlacklist(t *testing.T) {
 	}
 
 	tk.MustExec("insert into mysql.expr_pushdown_blacklist " +
-		"values('<', 'tikv,tiflash,tidb', 'for test'),('cast', 'tiflash', 'for test'),('date_format', 'tikv', 'for test')")
+		"values('<', 'tikv,tiflash,tidb', 'for test'),('cast', 'tiflash', 'for test'),('date_format', 'tikv', 'for test')," +
+		"('Cast.CastTimeAsDuration', 'tikv', 'for test')")
 	tk.MustExec("admin reload expr_pushdown_blacklist")
 
 	tk.MustExec("set @@session.tidb_isolation_read_engines = 'tiflash'")
@@ -692,8 +693,18 @@ func TestExprPushdownBlacklist(t *testing.T) {
 	require.Equal(t, "eq(date_format(test.t.b, \"%m\"), \"11\"), lt(test.t.b, 1994-01-01)", fmt.Sprintf("%v", rows[0][4]))
 	require.Equal(t, "gt(cast(test.t.a, decimal(10,2) BINARY), 10.10), gt(test.t.b, 1988-01-01)", fmt.Sprintf("%v", rows[2][4]))
 
+	// CastTimeAsString pushed to TiKV but CastTimeAsDuration not pushed
+	rows = tk.MustQuery("explain format = 'brief' SELECT * FROM t WHERE CAST(b AS CHAR) = '10:00:00';").Rows()
+	require.Equal(t, "cop[tikv]", fmt.Sprintf("%v", rows[1][2]))
+	require.Equal(t, "eq(cast(test.t.b, var_string(5)), \"10:00:00\")", fmt.Sprintf("%v", rows[1][4]))
+
+	rows = tk.MustQuery("explain format = 'brief' select * from test.t where hour(b) > 10").Rows()
+	require.Equal(t, "root", fmt.Sprintf("%v", rows[0][2]))
+	require.Equal(t, "gt(hour(cast(test.t.b, time)), 10)", fmt.Sprintf("%v", rows[0][4]))
+
 	tk.MustExec("delete from mysql.expr_pushdown_blacklist where name = '<' and store_type = 'tikv,tiflash,tidb' and reason = 'for test'")
 	tk.MustExec("delete from mysql.expr_pushdown_blacklist where name = 'date_format' and store_type = 'tikv' and reason = 'for test'")
+	tk.MustExec("delete from mysql.expr_pushdown_blacklist where name = 'Cast.CastTimeAsDuration' and store_type = 'tikv' and reason = 'for test'")
 	tk.MustExec("admin reload expr_pushdown_blacklist")
 }