expression: implement regexp_substr function pushdown (#39536)

close #39535

expression/expr_to_pb_test.go

@@ -1083,6 +1083,11 @@ func TestExprPushDownToFlash(t *testing.T) {
 	require.NoError(t, err)
 	exprs = append(exprs, function)
 
+	// regexp_substr: supported
+	function, err = NewFunction(mock.NewContext(), ast.RegexpSubstr, types.NewFieldType(mysql.TypeString), stringColumn, stringColumn, intColumn, intColumn, stringColumn)
+	require.NoError(t, err)
+	exprs = append(exprs, function)
+
 	// greatest
 	function, err = NewFunction(mock.NewContext(), ast.Greatest, types.NewFieldType(mysql.TypeLonglong), int32Column, intColumn)
 	require.NoError(t, err)

expression/expression.go

@@ -1165,7 +1165,7 @@ func scalarExprSupportedByFlash(function *ScalarFunction) bool {
 			return false
 		}
 		return true
-	case ast.Regexp, ast.RegexpLike, ast.RegexpInStr:
+	case ast.Regexp, ast.RegexpLike, ast.RegexpInStr, ast.RegexpSubstr:
 		funcCharset, funcCollation := function.Function.CharsetAndCollation()
 		if funcCharset == charset.CharsetBin && funcCollation == charset.CollationBin {
 			return false

planner/core/integration_test.go

@@ -7450,6 +7450,39 @@ func TestRegexpInstrPushDownToTiFlash(t *testing.T) {
 	tk.MustQuery("explain select regexp_instr(expr, pattern, 1, 1, 0, match_type) as res from test.t;").CheckAt([]int{0, 2, 4}, rows)
 }
 
+func TestRegexpSubstrPushDownToTiFlash(t *testing.T) {
+	store, dom := testkit.CreateMockStoreAndDomain(t)
+	tk := testkit.NewTestKit(t, store)
+
+	tk.MustExec("use test")
+	tk.MustExec("drop table if exists test.t;")
+	tk.MustExec("create table test.t (expr varchar(30), pattern varchar(30), pos int, occur int, match_type varchar(30));")
+	tk.MustExec("insert into test.t values ('123', '12.', 1, 1, ''), ('aBb', 'bb', 1, 1, 'i'), ('ab\nabc', '^abc$', 1, 1, 'm');")
+	tk.MustExec("set @@tidb_allow_mpp=1; set @@tidb_enforce_mpp=1")
+	tk.MustExec("set @@tidb_isolation_read_engines = 'tiflash'")
+
+	// Create virtual tiflash replica info.
+	is := dom.InfoSchema()
+	db, exists := is.SchemaByName(model.NewCIStr("test"))
+	require.True(t, exists)
+	for _, tblInfo := range db.Tables {
+		if tblInfo.Name.L == "t" {
+			tblInfo.TiFlashReplica = &model.TiFlashReplicaInfo{
+				Count:     1,
+				Available: true,
+			}
+		}
+	}
+
+	rows := [][]interface{}{
+		{"TableReader_9", "root", "data:ExchangeSender_8"},
+		{"└─ExchangeSender_8", "mpp[tiflash]", "ExchangeType: PassThrough"},
+		{"  └─Projection_4", "mpp[tiflash]", "regexp_substr(test.t.expr, test.t.pattern, 1, 1, test.t.match_type)->Column#7"},
+		{"    └─TableFullScan_7", "mpp[tiflash]", "keep order:false, stats:pseudo"},
+	}
+	tk.MustQuery("explain select regexp_substr(expr, pattern, 1, 1, match_type) as res from test.t;").CheckAt([]int{0, 2, 4}, rows)
+}
+
 func TestCastTimeAsDurationToTiFlash(t *testing.T) {
 	store, dom := testkit.CreateMockStoreAndDomain(t)
 	tk := testkit.NewTestKit(t, store)