planner: lateral join support | tidb-test=pr/2664

BUILD.bazel

@@ -1,3 +1,4 @@
+load("@io_bazel_rules_go//go:def.bzl", "go_binary", "go_library")
 load("@bazel_gazelle//:def.bzl", "gazelle")
 
 exports_files([
@@ -23,3 +24,19 @@ xcode_version(
     name = "xcode_version",
     version = "10.0",
 )
+
+go_library(
+    name = "tidb_lib",
+    srcs = ["test_lateral_simple.go"],
+    importpath = "github.com/pingcap/tidb",
+    deps = [
+        "//pkg/parser",
+        "//pkg/parser/format",
+        "//pkg/types/parser_driver",
+    ],
+)
+
+go_binary(
+    name = "tidb",
+    embed = [":tidb_lib"],
+)

pkg/errno/errcode.go

@@ -919,6 +919,7 @@ const (
 	ErrDefValGeneratedNamedFunctionIsNotAllowed              = 3770
 	ErrFKIncompatibleColumns                                 = 3780
 	ErrFunctionalIndexRowValueIsNotAllowed                   = 3800
+	ErrInvalidLateralJoin                                    = 3809
 	ErrNonBooleanExprForCheckConstraint                      = 3812
 	ErrColumnCheckConstraintReferencesOtherColumn            = 3813
 	ErrCheckConstraintNamedFunctionIsNotAllowed              = 3814

pkg/errno/errname.go

@@ -913,6 +913,7 @@ var MySQLErrName = map[uint16]*mysql.ErrMessage{
 	ErrFunctionalIndexOnField:                                mysql.Message("Expression index on a column is not supported. Consider using a regular index instead", nil),
 	ErrFKIncompatibleColumns:                                 mysql.Message("Referencing column '%s' and referenced column '%s' in foreign key constraint '%s' are incompatible.", nil),
 	ErrFunctionalIndexRowValueIsNotAllowed:                   mysql.Message("Expression of expression index '%s' cannot refer to a row value", nil),
+	ErrInvalidLateralJoin:                                    mysql.Message("Invalid use of LATERAL: %s", nil),
 	ErrNonBooleanExprForCheckConstraint:                      mysql.Message("An expression of non-boolean type specified to a check constraint '%s'.", nil),
 	ErrColumnCheckConstraintReferencesOtherColumn:            mysql.Message("Column check constraint '%s' references other column.", nil),
 	ErrCheckConstraintNamedFunctionIsNotAllowed:              mysql.Message("An expression of a check constraint '%s' contains disallowed function: %s.", nil),

pkg/parser/ast/dml.go

@@ -535,6 +535,11 @@ type TableSource struct {
 
 	// AsName is the alias name of the table source.
 	AsName CIStr
+
+	// Lateral indicates whether this is a LATERAL derived table.
+	// MySQL 8.0+ syntax: FROM t1, LATERAL (SELECT ...) AS dt
+	// LATERAL allows the derived table to reference columns from tables to its left.
+	Lateral bool
 }
 
 func (*TableSource) resultSet() {}
@@ -547,6 +552,11 @@ func (n *TableSource) Restore(ctx *format.RestoreCtx) error {
 		needParen = true
 	}
 
+	// Output LATERAL keyword if this is a LATERAL derived table
+	if n.Lateral {
+		ctx.WriteKeyWord("LATERAL ")
+	}
+
 	if tn, tnCase := n.Source.(*TableName); tnCase {
 		if needParen {
 			ctx.WritePlain("(")

pkg/parser/misc.go

@@ -508,6 +508,7 @@ var tokenMap = map[string]int{
 	"LAST_BACKUP":                    lastBackup,
 	"LAST":                           last,
 	"LASTVAL":                        lastval,
+	"LATERAL":                        lateral,
 	"LEADER":                         leader,
 	"LEADER_CONSTRAINTS":             leaderConstraints,
 	"LEADING":                        leading,

pkg/parser/mysql/errcode.go

@@ -948,6 +948,7 @@ const (
 	ErrFunctionalIndexOnField                                = 3762
 	ErrFKIncompatibleColumns                                 = 3780
 	ErrFunctionalIndexRowValueIsNotAllowed                   = 3800
+	ErrInvalidLateralJoin                                    = 3809
 	ErrDependentByFunctionalIndex                            = 3837
 	ErrInvalidJSONType                                       = 3853
 	ErrInvalidJsonValueForFuncIndex                          = 3903 //nolint: revive