From 1f314c2e91a4890034e52a1eafba31b6b70d8f78 Mon Sep 17 00:00:00 2001
From: ZhuoZhi <517770911@qq.com>
Date: Wed, 16 Jun 2021 15:12:37 +0800
Subject: [PATCH] cherry pick #25294 to release-5.1

Signed-off-by: ti-srebot <ti-srebot@pingcap.com>
---
 executor/index_merge_reader_test.go | 16 ++++++++++++++++
 planner/core/find_best_task.go      | 18 ++++++++++++++++++
 2 files changed, 34 insertions(+)

diff --git a/executor/index_merge_reader_test.go b/executor/index_merge_reader_test.go
index 9aa01c434d3c3..73322d3581755 100644
--- a/executor/index_merge_reader_test.go
+++ b/executor/index_merge_reader_test.go
@@ -67,6 +67,22 @@ func (s *testSuite1) TestIndexMergeReaderAndGeneratedColumn(c *C) {
 	tk.MustQuery("SELECT t0.c0 FROM t0 WHERE t0.c1 OR t0.c0").Check(testkit.Rows("1"))
 }
 
+// issue 25045
+func (s *testSuite1) TestIndexMergeReaderIssue25045(c *C) {
+	tk := testkit.NewTestKitWithInit(c, s.store)
+	tk.MustExec("use test")
+	tk.MustExec("drop table if exists t1")
+	tk.MustExec("create table t1(a int primary key, b int, c int, key(b), key(c));")
+	tk.MustExec("INSERT INTO t1 VALUES (10, 10, 10), (11, 11, 11)")
+	tk.MustQuery("explain format='brief' select /*+ use_index_merge(t1) */ * from t1 where c=10 or (b=10 and a=10);").Check(testkit.Rows(
+		"IndexMerge 0.01 root  ",
+		"├─IndexRangeScan(Build) 10.00 cop[tikv] table:t1, index:c(c) range:[10,10], keep order:false, stats:pseudo",
+		"├─TableRangeScan(Build) 1.00 cop[tikv] table:t1 range:[10,10], keep order:false, stats:pseudo",
+		"└─Selection(Probe) 0.01 cop[tikv]  or(eq(test.t1.c, 10), and(eq(test.t1.b, 10), eq(test.t1.a, 10)))",
+		"  └─TableRowIDScan 11.00 cop[tikv] table:t1 keep order:false, stats:pseudo"))
+	tk.MustQuery("select /*+ use_index_merge(t1) */ * from t1 where c=10 or (b=10 and a=10);").Check(testkit.Rows("10 10 10"))
+}
+
 func (s *testSuite1) TestIssue16910(c *C) {
 	tk := testkit.NewTestKitWithInit(c, s.store)
 	tk.MustExec("use test;")
diff --git a/planner/core/find_best_task.go b/planner/core/find_best_task.go
index 6a80a9e93bfb1..f9b233ff1d7c3 100644
--- a/planner/core/find_best_task.go
+++ b/planner/core/find_best_task.go
@@ -897,10 +897,28 @@ func (ds *DataSource) convertToPartialIndexScan(prop *property.PhysicalProperty,
 	return indexPlan, partialCost
 }
 
+func checkColinSchema(cols []*expression.Column, schema *expression.Schema) bool {
+	for _, col := range cols {
+		if schema.ColumnIndex(col) == -1 {
+			return false
+		}
+	}
+	return true
+}
+
 func (ds *DataSource) convertToPartialTableScan(prop *property.PhysicalProperty, path *util.AccessPath) (
 	tablePlan PhysicalPlan, partialCost float64) {
 	ts, partialCost, rowCount := ds.getOriginalPhysicalTableScan(prop, path, false)
 	overwritePartialTableScanSchema(ds, ts)
+	// remove ineffetive filter condition after overwriting physicalscan schema
+	newFilterConds := make([]expression.Expression, 0, len(path.TableFilters))
+	for _, cond := range ts.filterCondition {
+		cols := expression.ExtractColumns(cond)
+		if checkColinSchema(cols, ts.schema) {
+			newFilterConds = append(newFilterConds, cond)
+		}
+	}
+	ts.filterCondition = newFilterConds
 	rowSize := ds.TblColHists.GetAvgRowSize(ds.ctx, ts.schema.Columns, false, false)
 	sessVars := ds.ctx.GetSessionVars()
 	if len(ts.filterCondition) > 0 {