MySQL/MariaDB: return max length for text columns (#2133)

MySQL/MariaDB: return max length for text columns using `CHARACTER_MAXIMUM_LENGTH`.

 Tests:
 * add an integration test: `TestGetColumnsLength`
 * update `TestSyncTable3` since `TableInfo` isn't able to provide the column size

Co-authored-by: Pierre-Louis Bonicoli <pierre-louis.bonicoli@libregerbil.fr>
Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>
Reviewed-on: https://gitea.com/xorm/xorm/pulls/2133
Reviewed-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: Pierre-Louis Bonicoli <pilou@noreply.gitea.io>
Co-committed-by: Pierre-Louis Bonicoli <pilou@noreply.gitea.io>

dialects/mysql.go

@@ -399,7 +399,7 @@ func (db *mysql) GetColumns(queryer core.Queryer, ctx context.Context, tableName
 		"(SUBSTRING_INDEX(SUBSTRING(VERSION(), 4), '.', 1) = 2 && " +
 		"SUBSTRING_INDEX(SUBSTRING(VERSION(), 6), '-', 1) >= 7)))))"
 	s := "SELECT `COLUMN_NAME`, `IS_NULLABLE`, `COLUMN_DEFAULT`, `COLUMN_TYPE`," +
-		" `COLUMN_KEY`, `EXTRA`, `COLUMN_COMMENT`, " +
+		" `COLUMN_KEY`, `EXTRA`, `COLUMN_COMMENT`, `CHARACTER_MAXIMUM_LENGTH`, " +
 		alreadyQuoted + " AS NEEDS_QUOTE " +
 		"FROM `INFORMATION_SCHEMA`.`COLUMNS` WHERE `TABLE_SCHEMA` = ? AND `TABLE_NAME` = ?" +
 		" ORDER BY `COLUMNS`.ORDINAL_POSITION"
@@ -418,8 +418,8 @@ func (db *mysql) GetColumns(queryer core.Queryer, ctx context.Context, tableName
 
 		var columnName, nullableStr, colType, colKey, extra, comment string
 		var alreadyQuoted, isUnsigned bool
-		var colDefault *string
+		var colDefault, maxLength *string
-		err = rows.Scan(&columnName, &nullableStr, &colDefault, &colType, &colKey, &extra, &comment, &alreadyQuoted)
+		err = rows.Scan(&columnName, &nullableStr, &colDefault, &colType, &colKey, &extra, &comment, &maxLength, &alreadyQuoted)
 		if err != nil {
 			return nil, nil, err
 		}
@@ -478,6 +478,14 @@ func (db *mysql) GetColumns(queryer core.Queryer, ctx context.Context, tableName
 					}
 				}
 			}
+		} else {
+			switch colType {
+			case "MEDIUMTEXT", "LONGTEXT", "TEXT":
+				len1, err = strconv.Atoi(*maxLength)
+				if err != nil {
+					return nil, nil, err
+				}
+			}
 		}
 		if isUnsigned {
 			colType = "UNSIGNED " + colType

integrations/engine_test.go

@@ -288,3 +288,36 @@ func TestGetColumnsComment(t *testing.T) {
 	assert.Equal(t, comment, hasComment)
 	assert.Zero(t, noComment)
 }
+
+func TestGetColumnsLength(t *testing.T) {
+	var max_length int
+	switch testEngine.Dialect().URI().DBType {
+	case
+		schemas.POSTGRES:
+		max_length = 0
+	case
+		schemas.MYSQL:
+		max_length = 65535
+	default:
+		t.Skip()
+		return
+	}
+
+	type TestLengthStringStruct struct {
+		Content string `xorm:"TEXT NOT NULL"`
+	}
+
+	assertSync(t, new(TestLengthStringStruct))
+
+	tables, err := testEngine.DBMetas()
+	assert.NoError(t, err)
+	tableLengthStringName := testEngine.GetColumnMapper().Obj2Table("TestLengthStringStruct")
+	for _, table := range tables {
+		if table.Name == tableLengthStringName {
+			col := table.GetColumn("content")
+			assert.Equal(t, col.Length, max_length)
+			assert.Zero(t, col.Length2)
+			break
+		}
+	}
+}

integrations/session_schema_test.go

@@ -6,6 +6,7 @@ package integrations
 
 import (
 	"fmt"
+	"strings"
 	"testing"
 	"time"
 
@@ -248,7 +249,9 @@ func TestSyncTable3(t *testing.T) {
 	tableInfo, err := testEngine.TableInfo(new(SyncTable5))
 	assert.NoError(t, err)
 	assert.EqualValues(t, testEngine.Dialect().SQLType(tableInfo.GetColumn("name")), testEngine.Dialect().SQLType(tables[0].GetColumn("name")))
-	assert.EqualValues(t, testEngine.Dialect().SQLType(tableInfo.GetColumn("text")), testEngine.Dialect().SQLType(tables[0].GetColumn("text")))
+	/* Engine.DBMetas() returns the size of the column from the database but Engine.TableInfo() might not be able to guess the column size.
+	For example using MySQL/MariaDB: when utf-8 charset is used, "`xorm:"TEXT(21846)`" creates a MEDIUMTEXT column not a TEXT column. */
+	assert.True(t, testEngine.Dialect().SQLType(tables[0].GetColumn("text")) == testEngine.Dialect().SQLType(tableInfo.GetColumn("text")) || strings.HasPrefix(testEngine.Dialect().SQLType(tables[0].GetColumn("text")), testEngine.Dialect().SQLType(tableInfo.GetColumn("text"))+"("))
 	assert.EqualValues(t, testEngine.Dialect().SQLType(tableInfo.GetColumn("char")), testEngine.Dialect().SQLType(tables[0].GetColumn("char")))
 	assert.EqualValues(t, testEngine.Dialect().SQLType(tableInfo.GetColumn("ten_char")), testEngine.Dialect().SQLType(tables[0].GetColumn("ten_char")))
 	assert.EqualValues(t, testEngine.Dialect().SQLType(tableInfo.GetColumn("ten_var_char")), testEngine.Dialect().SQLType(tables[0].GetColumn("ten_var_char")))