ddl: make prefix index compatible with mysql 8.0 when prefix length e…

…qual to column length (#48296) close #48295
pingcap · Mar 12, 2024 · 5745d3d · 5745d3d
1 parent 15947c1
commit 5745d3d
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Showing 4 changed files with 66 additions and 2 deletions.
diff --git a/pkg/ddl/column.go b/pkg/ddl/column.go
@@ -631,7 +631,7 @@ func SetIdxColNameOffset(idxCol *model.IndexColumn, changingCol *model.ColumnInf
 	idxCol.Name = changingCol.Name
 	idxCol.Offset = changingCol.Offset
 	canPrefix := types.IsTypePrefixable(changingCol.GetType())
-	if !canPrefix || (changingCol.GetFlen() < idxCol.Length) {
+	if !canPrefix || (changingCol.GetFlen() <= idxCol.Length) {
 		idxCol.Length = types.UnspecifiedLength
 	}
 }

diff --git a/pkg/ddl/index.go b/pkg/ddl/index.go
@@ -113,7 +113,12 @@ func buildIndexColumns(ctx sessionctx.Context, columns []*model.ColumnInfo, inde
 			mvIndex = true
 		}
 		indexColLen := ip.Length
-		indexColumnLength, err := getIndexColumnLength(col, ip.Length)
+		if indexColLen != types.UnspecifiedLength &&
+			types.IsTypeChar(col.FieldType.GetType()) &&
+			indexColLen == col.FieldType.GetFlen() {
+			indexColLen = types.UnspecifiedLength
+		}
+		indexColumnLength, err := getIndexColumnLength(col, indexColLen)
 		if err != nil {
 			return nil, false, err
 		}

diff --git a/tests/integrationtest/r/table/index.result b/tests/integrationtest/r/table/index.result
@@ -31,3 +31,50 @@ Error 1062 (23000): Duplicate entry 'q' for key 't.idx_a'
 update ignore t set a = 'qcc' where a = 'rcc';
 Level	Code	Message
 Warning	1062	Duplicate entry 'q' for key 't.idx_a'
+drop table if exists t;
+create table t (id int, a varchar(64), b varchar(64), c varchar(64), index idx_a(a(64)));
+show create table t;
+Table	Create Table
+t	CREATE TABLE `t` (
+  `id` int(11) DEFAULT NULL,
+  `a` varchar(64) DEFAULT NULL,
+  `b` varchar(64) DEFAULT NULL,
+  `c` varchar(64) DEFAULT NULL,
+  KEY `idx_a` (`a`)
+) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_bin
+alter table t add index idx_b(b(64));
+show create table t;
+Table	Create Table
+t	CREATE TABLE `t` (
+  `id` int(11) DEFAULT NULL,
+  `a` varchar(64) DEFAULT NULL,
+  `b` varchar(64) DEFAULT NULL,
+  `c` varchar(64) DEFAULT NULL,
+  KEY `idx_a` (`a`),
+  KEY `idx_b` (`b`)
+) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_bin
+alter table t add index idx_c(c(32));
+show create table t;
+Table	Create Table
+t	CREATE TABLE `t` (
+  `id` int(11) DEFAULT NULL,
+  `a` varchar(64) DEFAULT NULL,
+  `b` varchar(64) DEFAULT NULL,
+  `c` varchar(64) DEFAULT NULL,
+  KEY `idx_a` (`a`),
+  KEY `idx_b` (`b`),
+  KEY `idx_c` (`c`(32))
+) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_bin
+alter table t modify column c varchar(32);
+show create table t;
+Table	Create Table
+t	CREATE TABLE `t` (
+  `id` int(11) DEFAULT NULL,
+  `a` varchar(64) DEFAULT NULL,
+  `b` varchar(64) DEFAULT NULL,
+  `c` varchar(32) DEFAULT NULL,
+  KEY `idx_a` (`a`),
+  KEY `idx_b` (`b`),
+  KEY `idx_c` (`c`)
+) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_bin
+drop table t;
diff --git a/tests/integrationtest/t/table/index.test b/tests/integrationtest/t/table/index.test
@@ -33,3 +33,15 @@ update t set a = 'qcc' where a = 'rcc';
 --enable_warnings;
 update ignore t set a = 'qcc' where a = 'rcc';
 --disable_warnings;
+
+# Test Issue 48295.
+drop table if exists t;
+create table t (id int, a varchar(64), b varchar(64), c varchar(64), index idx_a(a(64)));
+show create table t;
+alter table t add index idx_b(b(64));
+show create table t;
+alter table t add index idx_c(c(32));
+show create table t;
+alter table t modify column c varchar(32);
+show create table t;
+drop table t;