planner: do not remove the first row func if it is a constant (pingca…

…p#50020) close pingcap#38756
b41sh · Jan 10, 2024 · 1a5a72a · 1a5a72a
1 parent d505704
commit 1a5a72a
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Showing 3 changed files with 19 additions and 1 deletion.
diff --git a/pkg/executor/test/executor/BUILD.bazel b/pkg/executor/test/executor/BUILD.bazel
@@ -8,7 +8,7 @@ go_test(
         "main_test.go",
     ],
     flaky = True,
-    shard_count = 48,
+    shard_count = 49,
     deps = [
         "//pkg/config",
         "//pkg/ddl",

diff --git a/pkg/executor/test/executor/executor_test.go b/pkg/executor/test/executor/executor_test.go
@@ -2775,3 +2775,15 @@ func TestIssues40463(t *testing.T) {
 
 	tk.MustQuery("select  /*+ use_index_merge( `4f380f26-9af6-4df8-959d-ad6296eff914` ) */ /*+  stream_agg() */  approx_percentile( `4f380f26-9af6-4df8-959d-ad6296eff914`.`f7a9a4be-3728-449b-a5ea-df9b957eec67` , 77 ) as r0 , `4f380f26-9af6-4df8-959d-ad6296eff914`.`f7a9a4be-3728-449b-a5ea-df9b957eec67` as r1 from `4f380f26-9af6-4df8-959d-ad6296eff914` where not( IsNull( `4f380f26-9af6-4df8-959d-ad6296eff914`.`f7a9a4be-3728-449b-a5ea-df9b957eec67` ) ) and not( `4f380f26-9af6-4df8-959d-ad6296eff914`.`f7a9a4be-3728-449b-a5ea-df9b957eec67` in ( select `8a93bdc5-2214-4f96-b5a7-1ba4c0d396ae` from `07ccc74e-14c3-4685-bb41-c78a069b1a6d` where `4f380f26-9af6-4df8-959d-ad6296eff914`.`f7a9a4be-3728-449b-a5ea-df9b957eec67` in ( select `a60d6b5c-08bd-4a6d-b951-716162d004a5` from `ba35a09f-76f4-40aa-9b48-13154a24bdd2` where not( `4f380f26-9af6-4df8-959d-ad6296eff914`.`f7a9a4be-3728-449b-a5ea-df9b957eec67` between 'bpkfo' and '59' ) and not( `4f380f26-9af6-4df8-959d-ad6296eff914`.`f7a9a4be-3728-449b-a5ea-df9b957eec67` in ( select `fb753d37-6252-4bd3-9bd1-0059640e7861` from `ba35a09f-76f4-40aa-9b48-13154a24bdd2` where IsNull( `4f380f26-9af6-4df8-959d-ad6296eff914`.`f7a9a4be-3728-449b-a5ea-df9b957eec67` ) or not( `4f380f26-9af6-4df8-959d-ad6296eff914`.`43ca0135-1650-429b-8887-9eabcae2a234` in ( select `8a93bdc5-2214-4f96-b5a7-1ba4c0d396ae` from `07ccc74e-14c3-4685-bb41-c78a069b1a6d` where IsNull( `4f380f26-9af6-4df8-959d-ad6296eff914`.`43ca0135-1650-429b-8887-9eabcae2a234` ) and not( `4f380f26-9af6-4df8-959d-ad6296eff914`.`f7a9a4be-3728-449b-a5ea-df9b957eec67` between 'neud' and 'bpkfo' ) ) ) ) ) ) ) ) group by `4f380f26-9af6-4df8-959d-ad6296eff914`.`f7a9a4be-3728-449b-a5ea-df9b957eec67`;")
 }
+
+func TestIssue38756(t *testing.T) {
+	store := testkit.CreateMockStore(t)
+	tk := testkit.NewTestKit(t, store)
+
+	tk.MustExec("use test")
+	tk.MustExec("create table t (c1 int)")
+	tk.MustExec("insert into t values (1), (2), (3)")
+	tk.MustQuery("SELECT SQRT(1) FROM t").Check(testkit.Rows("1", "1", "1"))
+	tk.MustQuery("(SELECT DISTINCT SQRT(1) FROM t)").Check(testkit.Rows("1"))
+	tk.MustQuery("SELECT DISTINCT cast(1 as double) FROM t").Check(testkit.Rows("1"))
+}
diff --git a/pkg/planner/core/task.go b/pkg/planner/core/task.go
@@ -1891,6 +1891,12 @@ func RemoveUnnecessaryFirstRow(
 					// the firstrow in root task can not be removed.
 					break
 				}
+				// Skip if it's a constant.
+				// For SELECT DISTINCT SQRT(1) FROM t.
+				// We shouldn't remove the firstrow(SQRT(1)).
+				if _, ok := gbyExpr.(*expression.Constant); ok {
+					continue
+				}
 				if gbyExpr.Equal(sctx, aggFunc.Args[0]) {
 					canOptimize = true
 					firstRowFuncMap[aggFunc].Args[0] = finalGbyItems[j]