partition: fix exchange partition validition check for null value (#4…

…7208)

close #47167

pkg/ddl/partition.go

@@ -3578,6 +3578,14 @@ func checkExchangePartitionRecordValidation(w *worker, ptbl, ntbl table.Table, p
 			buf.WriteString(pi.Expr)
 			buf.WriteString(", %?) != %?")
 			paramList = append(paramList, pi.Num, index)
+			if index != 0 {
+				// TODO: if hash result can't be NULL, we can remove the check part.
+				// For example hash(id), but id is defined not NULL.
+				buf.WriteString(" or mod(")
+				buf.WriteString(pi.Expr)
+				buf.WriteString(", %?) is null")
+				paramList = append(paramList, pi.Num, index)
+			}
 		}
 	case model.PartitionTypeRange:
 		// Table has only one partition and has the maximum value
@@ -3691,13 +3699,17 @@ func buildCheckSQLConditionForRangeExprPartition(pi *model.PartitionInfo, index
 		paramList = append(paramList, driver.UnwrapFromSingleQuotes(pi.Definitions[index].LessThan[0]))
 	} else if index == len(pi.Definitions)-1 && strings.EqualFold(pi.Definitions[index].LessThan[0], partitionMaxValue) {
 		buf.WriteString(pi.Expr)
-		buf.WriteString(" < %?")
+		buf.WriteString(" < %? or ")
+		buf.WriteString(pi.Expr)
+		buf.WriteString(" is null")
 		paramList = append(paramList, driver.UnwrapFromSingleQuotes(pi.Definitions[index-1].LessThan[0]))
 	} else {
 		buf.WriteString(pi.Expr)
 		buf.WriteString(" < %? or ")
 		buf.WriteString(pi.Expr)
-		buf.WriteString(" >= %?")
+		buf.WriteString(" >= %? or ")
+		buf.WriteString(pi.Expr)
+		buf.WriteString(" is null")
 		paramList = append(paramList, driver.UnwrapFromSingleQuotes(pi.Definitions[index-1].LessThan[0]), driver.UnwrapFromSingleQuotes(pi.Definitions[index].LessThan[0]))
 	}
 	return buf.String(), paramList

pkg/ddl/tests/partition/BUILD.bazel

@@ -8,7 +8,7 @@ go_test(
         "main_test.go",
     ],
     flaky = True,
-    shard_count = 44,
+    shard_count = 45,
     deps = [
         "//pkg/config",
         "//pkg/ddl",

pkg/ddl/tests/partition/db_partition_test.go

@@ -3413,3 +3413,42 @@ func TestAlterLastIntervalPartition(t *testing.T) {
 }
 
 // TODO: check EXCHANGE how it handles null (for all types of partitioning!!!)
+func TestExchangeValidateHandleNullValue(t *testing.T) {
+	store := testkit.CreateMockStore(t)
+
+	tk := testkit.NewTestKit(t, store)
+	tk.MustExec("use test")
+
+	tk.MustExec(`CREATE TABLE t1 (id int, c varchar(128)) PARTITION BY HASH (id) PARTITIONS 3`)
+	tk.MustExec(`CREATE TABLE t2 (id int, c varchar(128))`)
+	tk.MustExec(`insert into t1 values(null, 'a1')`)
+	tk.MustExec(`insert into t2 values(null, 'b2')`)
+	tk.MustQuery(`select id, c from t1 partition(p0)`).Check(testkit.Rows("<nil> a1"))
+	tk.MustContainErrMsg(`alter table t1 EXCHANGE PARTITION p1 WITH TABLE t2`,
+		"[ddl:1737]Found a row that does not match the partition")
+	tk.MustExec(`alter table t1 EXCHANGE PARTITION p0 WITH TABLE t2`)
+
+	tk.MustExec(`CREATE TABLE t3 (id int, c date) PARTITION BY HASH (year(c)) PARTITIONS 12`)
+	tk.MustExec(`CREATE TABLE t4 (id int, c date)`)
+	tk.MustExec(`insert into t3 values(1, null)`)
+	tk.MustExec(`insert into t4 values(2, null)`)
+	tk.MustQuery(`select id, c from t3 partition(p0)`).Check(testkit.Rows("1 <nil>"))
+	tk.MustContainErrMsg(`alter table t3 EXCHANGE PARTITION p1 WITH TABLE t4`,
+		"[ddl:1737]Found a row that does not match the partition")
+	tk.MustExec(`alter table t3 EXCHANGE PARTITION p0 WITH TABLE t4`)
+
+	tk.MustExec(`CREATE TABLE t5 (id int, c varchar(128)) partition by range (id)(
+		partition p0 values less than (10), 
+		partition p1 values less than (20),
+		partition p2 values less than (maxvalue))`)
+	tk.MustExec(`CREATE TABLE t6 (id int, c varchar(128))`)
+	tk.MustExec(`insert into t5 values(null, 'a5')`)
+	tk.MustExec(`insert into t6 values(null, 'b6')`)
+	tk.MustQuery(`select id, c from t5 partition(p0)`).Check(testkit.Rows("<nil> a5"))
+	tk.MustContainErrMsg(`alter table t5 EXCHANGE PARTITION p1 WITH TABLE t6`,
+		"[ddl:1737]Found a row that does not match the partition")
+	tk.MustContainErrMsg(`alter table t5 EXCHANGE PARTITION p2 WITH TABLE t6`,
+		"[ddl:1737]Found a row that does not match the partition")
+	tk.MustExec(`alter table t5 EXCHANGE PARTITION p0 WITH TABLE t6`)
+	// TODO: add "partition by range columns(a, b, c)" test cases.
+}