// CopySchemaShard copies the schema from a source tablet to the
// specified shard. The schema is applied directly on the master of
// the destination shard, and is propogated to the replicas through
// binlogs.
func (wr *Wrangler) CopySchemaShard(ctx context.Context, sourceTabletAlias *topodatapb.TabletAlias, tables, excludeTables []string, includeViews bool, destKeyspace, destShard string) error {
destShardInfo, err := wr.ts.GetShard(ctx, destKeyspace, destShard)
if err != nil {
return err
}
sourceSd, err := wr.GetSchema(ctx, sourceTabletAlias, tables, excludeTables, includeViews)
if err != nil {
return err
}
destSd, err := wr.GetSchema(ctx, destShardInfo.MasterAlias, tables, excludeTables, includeViews)
if err != nil {
destSd = nil
}
if destSd != nil {
diffs := tmutils.DiffSchemaToArray("source", sourceSd, "dest", destSd)
if diffs == nil {
// Return early because dest has already the same schema as source.
return nil
}
}
createSQL := tmutils.SchemaDefinitionToSQLStrings(sourceSd)
destTabletInfo, err := wr.ts.GetTablet(ctx, destShardInfo.MasterAlias)
if err != nil {
return err
}
for i, sqlLine := range createSQL {
err = wr.applySQLShard(ctx, destTabletInfo, sqlLine, i == len(createSQL)-1)
if err != nil {
return err
}
}
return nil
}
func (exec *TabletExecutor) preflightSchemaChanges(ctx context.Context, sqls []string) error {
schemaDiffs, err := exec.wr.TabletManagerClient().PreflightSchema(ctx, exec.tablets[0], sqls)
if err != nil {
return err
}
parsedDDLs, err := parseDDLs(sqls)
if err != nil {
return err
}
for i, schemaDiff := range schemaDiffs {
diffs := tmutils.DiffSchemaToArray(
"BeforeSchema",
schemaDiff.BeforeSchema,
"AfterSchema",
schemaDiff.AfterSchema)
if len(diffs) == 0 {
if parsedDDLs[i].Action == sqlparser.DropStr && parsedDDLs[i].IfExists {
// DROP IF EXISTS on a nonexistent table does not change the schema. It's safe to ignore.
continue
}
return fmt.Errorf("Schema change: '%s' does not introduce any table definition change.", sqls[i])
}
}
exec.schemaDiffs = schemaDiffs
return nil
}
// compareSchemas returns nil if the schema of the two tablets referenced by
// "sourceAlias" and "destAlias" are identical. Otherwise, the difference is
// returned as []string.
func (wr *Wrangler) compareSchemas(ctx context.Context, sourceAlias, destAlias *topodatapb.TabletAlias, tables, excludeTables []string, includeViews bool) ([]string, error) {
sourceSd, err := wr.GetSchema(ctx, sourceAlias, tables, excludeTables, includeViews)
if err != nil {
return nil, fmt.Errorf("failed to get schema from tablet %v. err: %v", sourceAlias, err)
}
destSd, err := wr.GetSchema(ctx, destAlias, tables, excludeTables, includeViews)
if err != nil {
return nil, fmt.Errorf("failed to get schema from tablet %v. err: %v", destAlias, err)
}
return tmutils.DiffSchemaToArray("source", sourceSd, "dest", destSd), nil
}
func (exec *TabletExecutor) preflightSchemaChanges(ctx context.Context, sqls []string) error {
exec.schemaDiffs = make([]*tmutils.SchemaChangeResult, len(sqls))
for i := range sqls {
schemaDiff, err := exec.tmClient.PreflightSchema(
ctx, exec.tabletInfos[0], sqls[i])
if err != nil {
return err
}
exec.schemaDiffs[i] = schemaDiff
diffs := tmutils.DiffSchemaToArray(
"BeforeSchema",
exec.schemaDiffs[i].BeforeSchema,
"AfterSchema",
exec.schemaDiffs[i].AfterSchema)
if len(diffs) == 0 {
return fmt.Errorf("Schema change: '%s' does not introduce any table definition change.", sqls[i])
}
}
return nil
}
func (wr *Wrangler) applySchemaShard(ctx context.Context, shardInfo *topo.ShardInfo, preflight *tmutils.SchemaChangeResult, masterTabletAlias *topodatapb.TabletAlias, change string, newParentTabletAlias *topodatapb.TabletAlias, force bool, waitSlaveTimeout time.Duration) (*tmutils.SchemaChangeResult, error) {
// find all the shards we need to handle
aliases, err := wr.ts.FindAllTabletAliasesInShard(ctx, shardInfo.Keyspace(), shardInfo.ShardName())
if err != nil {
return nil, err
}
// build the array of tabletStatus we're going to use
statusArray := make([]*tabletStatus, 0, len(aliases)-1)
for _, alias := range aliases {
if alias == masterTabletAlias {
// we skip the master
continue
}
ti, err := wr.ts.GetTablet(ctx, alias)
if err != nil {
return nil, err
}
statusArray = append(statusArray, &tabletStatus{ti: ti})
}
// get schema on all tablets.
log.Infof("Getting schema on all tablets for shard %v/%v", shardInfo.Keyspace(), shardInfo.ShardName())
wg := &sync.WaitGroup{}
for _, status := range statusArray {
wg.Add(1)
go func(status *tabletStatus) {
status.beforeSchema, status.lastError = wr.tmc.GetSchema(ctx, status.ti, nil, nil, false)
wg.Done()
}(status)
}
wg.Wait()
// quick check for errors
for _, status := range statusArray {
if status.lastError != nil {
return nil, fmt.Errorf("Error getting schema on tablet %v: %v", status.ti.AliasString(), status.lastError)
}
}
// check all tablets have the same schema as the master's
// BeforeSchema. If not, we shouldn't proceed
log.Infof("Checking schema on all tablets")
for _, status := range statusArray {
diffs := tmutils.DiffSchemaToArray("master", preflight.BeforeSchema, topoproto.TabletAliasString(status.ti.Alias), status.beforeSchema)
if len(diffs) > 0 {
if force {
log.Warningf("Tablet %v has inconsistent schema, ignoring: %v", status.ti.AliasString(), strings.Join(diffs, "\n"))
} else {
return nil, fmt.Errorf("Tablet %v has inconsistent schema: %v", status.ti.AliasString(), strings.Join(diffs, "\n"))
}
}
}
// we're good, just send to the master
log.Infof("Applying schema change to master")
sc := &tmutils.SchemaChange{
SQL: change,
Force: force,
AllowReplication: true,
BeforeSchema: preflight.BeforeSchema,
AfterSchema: preflight.AfterSchema,
}
return wr.ApplySchema(ctx, masterTabletAlias, sc)
}
// ApplySchemaChange will apply the schema change to the given database.
func (mysqld *Mysqld) ApplySchemaChange(dbName string, change *tmutils.SchemaChange) (*tmutils.SchemaChangeResult, error) {
// check current schema matches
beforeSchema, err := mysqld.GetSchema(dbName, nil, nil, true)
if err != nil {
return nil, err
}
if change.BeforeSchema != nil {
schemaDiffs := tmutils.DiffSchemaToArray("actual", beforeSchema, "expected", change.BeforeSchema)
if len(schemaDiffs) > 0 {
for _, msg := range schemaDiffs {
log.Warningf("BeforeSchema differs: %v", msg)
}
// let's see if the schema was already applied
if change.AfterSchema != nil {
schemaDiffs = tmutils.DiffSchemaToArray("actual", beforeSchema, "expected", change.AfterSchema)
if len(schemaDiffs) == 0 {
// no diff between the schema we expect
// after the change and the current
// schema, we already applied it
return &tmutils.SchemaChangeResult{
BeforeSchema: beforeSchema,
AfterSchema: beforeSchema}, nil
}
}
if change.Force {
log.Warningf("BeforeSchema differs, applying anyway")
} else {
return nil, fmt.Errorf("BeforeSchema differs")
}
}
}
sql := change.SQL
if !change.AllowReplication {
sql = "SET sql_log_bin = 0;\n" + sql
}
// add a 'use XXX' in front of the SQL
sql = "USE " + dbName + ";\n" + sql
// execute the schema change using an external mysql process
// (to benefit from the extra commands in mysql cli)
if err = mysqld.executeMysqlCommands(mysqld.dba.Uname, sql); err != nil {
return nil, err
}
// get AfterSchema
afterSchema, err := mysqld.GetSchema(dbName, nil, nil, true)
if err != nil {
return nil, err
}
// compare to the provided AfterSchema
if change.AfterSchema != nil {
schemaDiffs := tmutils.DiffSchemaToArray("actual", afterSchema, "expected", change.AfterSchema)
if len(schemaDiffs) > 0 {
for _, msg := range schemaDiffs {
log.Warningf("AfterSchema differs: %v", msg)
}
if change.Force {
log.Warningf("AfterSchema differs, not reporting error")
} else {
return nil, fmt.Errorf("AfterSchema differs")
}
}
}
return &tmutils.SchemaChangeResult{BeforeSchema: beforeSchema, AfterSchema: afterSchema}, nil
}