Merge pull request #595 from github/support-generated-columns

Support for GENERATED (aka virtual) columns

Author: Shlomi Noach

doc/requirements-and-limitations.md

@@ -26,10 +26,6 @@ The `SUPER` privilege is required for `STOP SLAVE`, `START SLAVE` operations. Th
 
 - Triggers are not supported. They may be supported in the future.
 
-- MySQL 5.7 generated columns are not supported. They may be supported in the future.
-
-- MySQL 5.7 `POINT` column type is not supported.
-
 - MySQL 5.7 `JSON` columns are supported but not as part of `PRIMARY KEY`
 
 - The two _before_ & _after_ tables must share a `PRIMARY KEY` or other `UNIQUE KEY`. This key will be used by `gh-ost` to iterate through the table rows when copying. [Read more](shared-key.md)
@@ -53,4 +49,4 @@ The `SUPER` privilege is required for `STOP SLAVE`, `START SLAVE` operations. Th
 
 - Migrating a `FEDERATED` table is unsupported and is irrelevant to the problem `gh-ost` tackles.
 
-- `ALTER TABLE ... RENAME TO some_other_name` is not supported (and you shouldn't use `gh-ost` for such a trivial operation).
+- `ALTER TABLE ... RENAME TO some_other_name` is not supported (and you shouldn't use `gh-ost` for such a trivial operation).

go/base/context.go

@@ -186,8 +186,10 @@ type MigrationContext struct {
 
 	OriginalTableColumnsOnApplier    *sql.ColumnList
 	OriginalTableColumns             *sql.ColumnList
+	OriginalTableVirtualColumns      *sql.ColumnList
 	OriginalTableUniqueKeys          [](*sql.UniqueKey)
 	GhostTableColumns                *sql.ColumnList
+	GhostTableVirtualColumns         *sql.ColumnList
 	GhostTableUniqueKeys             [](*sql.UniqueKey)
 	UniqueKey                        *sql.UniqueKey
 	SharedColumns                    *sql.ColumnList

go/logic/applier.go

@@ -117,7 +117,7 @@ func (this *Applier) validateAndReadTimeZone() error {
 // readTableColumns reads table columns on applier
 func (this *Applier) readTableColumns() (err error) {
 	log.Infof("Examining table structure on applier")
-	this.migrationContext.OriginalTableColumnsOnApplier, err = mysql.GetTableColumns(this.db, this.migrationContext.DatabaseName, this.migrationContext.OriginalTableName)
+	this.migrationContext.OriginalTableColumnsOnApplier, _, err = mysql.GetTableColumns(this.db, this.migrationContext.DatabaseName, this.migrationContext.OriginalTableName)
 	if err != nil {
 		return err
 	}

go/logic/inspect.go

@@ -89,24 +89,24 @@ func (this *Inspector) ValidateOriginalTable() (err error) {
 	return nil
 }
 
-func (this *Inspector) InspectTableColumnsAndUniqueKeys(tableName string) (columns *sql.ColumnList, uniqueKeys [](*sql.UniqueKey), err error) {
+func (this *Inspector) InspectTableColumnsAndUniqueKeys(tableName string) (columns *sql.ColumnList, virtualColumns *sql.ColumnList, uniqueKeys [](*sql.UniqueKey), err error) {
 	uniqueKeys, err = this.getCandidateUniqueKeys(tableName)
 	if err != nil {
-		return columns, uniqueKeys, err
+		return columns, virtualColumns, uniqueKeys, err
 	}
 	if len(uniqueKeys) == 0 {
-		return columns, uniqueKeys, fmt.Errorf("No PRIMARY nor UNIQUE key found in table! Bailing out")
+		return columns, virtualColumns, uniqueKeys, fmt.Errorf("No PRIMARY nor UNIQUE key found in table! Bailing out")
 	}
-	columns, err = mysql.GetTableColumns(this.db, this.migrationContext.DatabaseName, tableName)
+	columns, virtualColumns, err = mysql.GetTableColumns(this.db, this.migrationContext.DatabaseName, tableName)
 	if err != nil {
-		return columns, uniqueKeys, err
+		return columns, virtualColumns, uniqueKeys, err
 	}
 
-	return columns, uniqueKeys, nil
+	return columns, virtualColumns, uniqueKeys, nil
 }
 
 func (this *Inspector) InspectOriginalTable() (err error) {
-	this.migrationContext.OriginalTableColumns, this.migrationContext.OriginalTableUniqueKeys, err = this.InspectTableColumnsAndUniqueKeys(this.migrationContext.OriginalTableName)
+	this.migrationContext.OriginalTableColumns, this.migrationContext.OriginalTableVirtualColumns, this.migrationContext.OriginalTableUniqueKeys, err = this.InspectTableColumnsAndUniqueKeys(this.migrationContext.OriginalTableName)
 	if err != nil {
 		return err
 	}
@@ -122,7 +122,7 @@ func (this *Inspector) inspectOriginalAndGhostTables() (err error) {
 		return fmt.Errorf("It seems like table structure is not identical between master and replica. This scenario is not supported.")
 	}
 
-	this.migrationContext.GhostTableColumns, this.migrationContext.GhostTableUniqueKeys, err = this.InspectTableColumnsAndUniqueKeys(this.migrationContext.GetGhostTableName())
+	this.migrationContext.GhostTableColumns, this.migrationContext.GhostTableVirtualColumns, this.migrationContext.GhostTableUniqueKeys, err = this.InspectTableColumnsAndUniqueKeys(this.migrationContext.GetGhostTableName())
 	if err != nil {
 		return err
 	}
@@ -166,7 +166,7 @@ func (this *Inspector) inspectOriginalAndGhostTables() (err error) {
 		}
 	}
 
-	this.migrationContext.SharedColumns, this.migrationContext.MappedSharedColumns = this.getSharedColumns(this.migrationContext.OriginalTableColumns, this.migrationContext.GhostTableColumns, this.migrationContext.ColumnRenameMap)
+	this.migrationContext.SharedColumns, this.migrationContext.MappedSharedColumns = this.getSharedColumns(this.migrationContext.OriginalTableColumns, this.migrationContext.GhostTableColumns, this.migrationContext.OriginalTableVirtualColumns, this.migrationContext.GhostTableVirtualColumns, this.migrationContext.ColumnRenameMap)
 	log.Infof("Shared columns are %s", this.migrationContext.SharedColumns)
 	// By fact that a non-empty unique key exists we also know the shared columns are non-empty
 
@@ -692,7 +692,7 @@ func (this *Inspector) getSharedUniqueKeys(originalUniqueKeys, ghostUniqueKeys [
 }
 
 // getSharedColumns returns the intersection of two lists of columns in same order as the first list
-func (this *Inspector) getSharedColumns(originalColumns, ghostColumns *sql.ColumnList, columnRenameMap map[string]string) (*sql.ColumnList, *sql.ColumnList) {
+func (this *Inspector) getSharedColumns(originalColumns, ghostColumns *sql.ColumnList, originalVirtualColumns, ghostVirtualColumns *sql.ColumnList, columnRenameMap map[string]string) (*sql.ColumnList, *sql.ColumnList) {
 	sharedColumnNames := []string{}
 	for _, originalColumn := range originalColumns.Names() {
 		isSharedColumn := false
@@ -709,6 +709,16 @@ func (this *Inspector) getSharedColumns(originalColumns, ghostColumns *sql.Colum
 				isSharedColumn = false
 			}
 		}
+		for _, virtualColumn := range originalVirtualColumns.Names() {
+			if strings.EqualFold(originalColumn, virtualColumn) {
+				isSharedColumn = false
+			}
+		}
+		for _, virtualColumn := range ghostVirtualColumns.Names() {
+			if strings.EqualFold(originalColumn, virtualColumn) {
+				isSharedColumn = false
+			}
+		}
 		if isSharedColumn {
 			sharedColumnNames = append(sharedColumnNames, originalColumn)
 		}

go/mysql/utils.go

@@ -8,6 +8,7 @@ package mysql
 import (
 	gosql "database/sql"
 	"fmt"
+	"strings"
 	"sync"
 	"time"
 
@@ -178,26 +179,32 @@ func GetInstanceKey(db *gosql.DB) (instanceKey *InstanceKey, err error) {
 }
 
 // GetTableColumns reads column list from given table
-func GetTableColumns(db *gosql.DB, databaseName, tableName string) (*sql.ColumnList, error) {
+func GetTableColumns(db *gosql.DB, databaseName, tableName string) (*sql.ColumnList, *sql.ColumnList, error) {
 	query := fmt.Sprintf(`
 		show columns from %s.%s
 		`,
 		sql.EscapeName(databaseName),
 		sql.EscapeName(tableName),
 	)
 	columnNames := []string{}
+	virtualColumnNames := []string{}
 	err := sqlutils.QueryRowsMap(db, query, func(rowMap sqlutils.RowMap) error {
-		columnNames = append(columnNames, rowMap.GetString("Field"))
+		columnName := rowMap.GetString("Field")
+		columnNames = append(columnNames, columnName)
+		if strings.Contains(rowMap.GetString("Extra"), " GENERATED") {
+			log.Debugf("%s is a generated column", columnName)
+			virtualColumnNames = append(virtualColumnNames, columnName)
+		}
 		return nil
 	})
 	if err != nil {
-		return nil, err
+		return nil, nil, err
 	}
 	if len(columnNames) == 0 {
-		return nil, log.Errorf("Found 0 columns on %s.%s. Bailing out",
+		return nil, nil, log.Errorf("Found 0 columns on %s.%s. Bailing out",
 			sql.EscapeName(databaseName),
 			sql.EscapeName(tableName),
 		)
 	}
-	return sql.NewColumnList(columnNames), nil
+	return sql.NewColumnList(columnNames), sql.NewColumnList(virtualColumnNames), nil
 }

localtests/generated-columns-add57/create.sql

@@ -0,0 +1,29 @@
+drop table if exists gh_ost_test;
+create table gh_ost_test (
+  id int auto_increment,
+  a int not null,
+  b int not null,
+  primary key(id)
+) auto_increment=1;
+
+drop event if exists gh_ost_test;
+delimiter ;;
+create event gh_ost_test
+  on schedule every 1 second
+  starts current_timestamp
+  ends current_timestamp + interval 60 second
+  on completion not preserve
+  enable
+  do
+begin
+  insert into gh_ost_test (id, a, b) values (null, 2,3);
+  insert into gh_ost_test (id, a, b) values (null, 2,4);
+  insert into gh_ost_test (id, a, b) values (null, 2,5);
+  insert into gh_ost_test (id, a, b) values (null, 2,6);
+  insert into gh_ost_test (id, a, b) values (null, 2,7);
+  insert into gh_ost_test (id, a, b) values (null, 2,8);
+  insert into gh_ost_test (id, a, b) values (null, 2,9);
+  insert into gh_ost_test (id, a, b) values (null, 2,0);
+  insert into gh_ost_test (id, a, b) values (null, 2,1);
+  insert into gh_ost_test (id, a, b) values (null, 2,2);
+end ;;

localtests/generated-columns-add57/extra_args

@@ -0,0 +1 @@
+--alter="add column sum_ab int as (a + b) virtual not null"

localtests/generated-columns-add57/ghost_columns

@@ -0,0 +1 @@
+id, a, b

localtests/generated-columns-add57/ignore_versions

@@ -0,0 +1 @@
+(5.5|5.6)

localtests/generated-columns-add57/order_by

@@ -0,0 +1 @@
+id