From 9014ceee698a9976110bf2f3195d8da21612e4af Mon Sep 17 00:00:00 2001
From: Maxwell <passagesfall@gmail.com>
Date: Fri, 15 May 2020 14:38:19 +0800
Subject: [PATCH] ddl: fix bug when add expression index (#17151)

---
 ddl/db_integration_test.go |  6 ++++++
 ddl/ddl_api.go             | 16 ++++++++++++++++
 ddl/index.go               |  8 ++++++++
 3 files changed, 30 insertions(+)

diff --git a/ddl/db_integration_test.go b/ddl/db_integration_test.go
index fc46f3fbc8..c9dfb1d1f6 100644
--- a/ddl/db_integration_test.go
+++ b/ddl/db_integration_test.go
@@ -2094,6 +2094,12 @@ func (s *testIntegrationSuite7) TestAddExpressionIndex(c *C) {
 
 	tk.MustQuery("select * from t;").Check(testkit.Rows("1 2.1"))
 
+	// Issue #17111
+	tk.MustExec("drop table if exists t1")
+	tk.MustExec("create table t1 (a varchar(10), b varchar(10));")
+	tk.MustExec("alter table t1 add unique index ei_ab ((concat(a, b)));")
+	tk.MustExec("alter table t1 alter index ei_ab invisible;")
+
 	// Test experiment switch.
 	config.GetGlobalConfig().Experimental.AllowsExpressionIndex = false
 	tk.MustGetErrMsg("create index d on t((a+1))", "[ddl:8200]Unsupported creating expression index without allow-expression-index in config")
diff --git a/ddl/ddl_api.go b/ddl/ddl_api.go
index e25ddba05d..be3d7f33b8 100644
--- a/ddl/ddl_api.go
+++ b/ddl/ddl_api.go
@@ -1133,16 +1133,32 @@ func getPrimaryKey(tblInfo *model.TableInfo) *model.IndexInfo {
 			// table has explicit primary key
 			return key
 		}
+		// The case index without any columns should never happen, but still do a check here
+		if len(key.Columns) == 0 {
+			continue
+		}
 		// find the first unique key with NOT NULL columns
 		if implicitPK == nil && key.Unique {
 			// ensure all columns in unique key have NOT NULL flag
 			allColNotNull := true
+			skip := false
 			for _, idxCol := range key.Columns {
 				col := model.FindColumnInfo(tblInfo.Cols(), idxCol.Name.L)
+				// This index has a column in DeleteOnly state,
+				// or it is expression index (it defined on a hidden column),
+				// it can not be implicit PK, go to next index iterator
+				if col == nil || col.Hidden {
+					skip = true
+					break
+				}
 				if !mysql.HasNotNullFlag(col.Flag) {
 					allColNotNull = false
+					break
 				}
 			}
+			if skip {
+				continue
+			}
 			if allColNotNull {
 				implicitPK = key
 			}
diff --git a/ddl/index.go b/ddl/index.go
index 1fa3c1c5f1..aa36b220ec 100755
--- a/ddl/index.go
+++ b/ddl/index.go
@@ -483,6 +483,14 @@ func (w *worker) onCreateIndex(d *ddlCtx, t *meta.Meta, job *model.Job, isPK boo
 		indexInfo.Unique = unique
 		indexInfo.ID = allocateIndexID(tblInfo)
 		tblInfo.Indices = append(tblInfo.Indices, indexInfo)
+
+		// Here we need do this check before set state to `DeleteOnly`,
+		// because if hidden columns has been set to `DeleteOnly`,
+		// the `DeleteOnly` columns are missing when we do this check.
+		if err := checkInvisibleIndexOnPK(tblInfo); err != nil {
+			job.State = model.JobStateCancelled
+			return ver, err
+		}
 		logutil.BgLogger().Info("[ddl] run add index job", zap.String("job", job.String()), zap.Reflect("indexInfo", indexInfo))
 	}
 	originalState := indexInfo.State