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CopySchemaShard: apply changes with foreign key checks disabled #4722

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CopySchemaShard: apply changes with foreign key checks disabled #4722

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8 changes: 8 additions & 0 deletions go/vt/wrangler/schema.go
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Original file line number Diff line number Diff line change
Expand Up @@ -323,6 +323,12 @@ func (wr *Wrangler) CopySchemaShard(ctx context.Context, sourceTabletAlias *topo
return fmt.Errorf("GetSchema(%v, %v, %v, %v) failed: %v", sourceTabletAlias, tables, excludeTables, includeViews, err)
}
createSQL := tmutils.SchemaDefinitionToSQLStrings(sourceSd)

// We're not clever enough to create tables in an order that's fk friendly,
// so we disable fk checks for the remainder of the (non-pooled) db connection
// using a session variable.
createSQL = append([]string{"set foreign_key_checks = 0"}, createSQL...)

destTabletInfo, err := wr.ts.GetTablet(ctx, destShardInfo.MasterAlias)
if err != nil {
return fmt.Errorf("GetTablet(%v) failed: %v", destShardInfo.MasterAlias, err)
Expand Down Expand Up @@ -434,6 +440,8 @@ func (wr *Wrangler) applySQLShard(ctx context.Context, tabletInfo *topo.TabletIn
ctx, cancel := context.WithTimeout(ctx, 30*time.Second)
defer cancel()
// Need to make sure that we enable binlog, since we're only applying the statement on masters.
// Do not set "usePool" to true. The SQL statements may change session settings, like
// disabling foreign key checks.
_, err = wr.tmc.ExecuteFetchAsDba(ctx, tabletInfo.Tablet, false, []byte(filledChange), 0, false, reloadSchema)
return err
}
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2 changes: 2 additions & 0 deletions go/vt/wrangler/testlib/copy_schema_shard_test.go
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Expand Up @@ -99,6 +99,7 @@ func copySchema(t *testing.T, useShardAsSource bool) {
sourceRdonly.FakeMysqlDaemon.Schema = schema

changeToDb := "USE vt_ks"
disableFkChecksSession := "set foreign_key_checks = 0"
createDb := "CREATE DATABASE `vt_ks` /*!40100 DEFAULT CHARACTER SET utf8 */"
createTable := "CREATE TABLE `vt_ks`.`table1` (\n" +
" `id` bigint(20) NOT NULL AUTO_INCREMENT,\n" +
Expand Down Expand Up @@ -140,6 +141,7 @@ func copySchema(t *testing.T, useShardAsSource bool) {

// The destination table is asked to create the new schema.
destinationMasterDb.AddQuery(changeToDb, &sqltypes.Result{})
destinationMasterDb.AddQuery(disableFkChecksSession, &sqltypes.Result{})
destinationMasterDb.AddQuery(createDb, &sqltypes.Result{})
destinationMasterDb.AddQuery(createTable, &sqltypes.Result{})
destinationMasterDb.AddQuery(createTableView, &sqltypes.Result{})
Expand Down