示例#1
0
文件: domain.go 项目: pingcap/tidb
// tryLoadSchemaDiffs tries to only load latest schema changes.
// Returns true if the schema is loaded successfully.
// Returns false if the schema can not be loaded by schema diff, then we need to do full load.
func (do *Domain) tryLoadSchemaDiffs(m *meta.Meta, usedVersion, newVersion int64) (bool, error) {
	if usedVersion == initialVersion || newVersion-usedVersion > maxNumberOfDiffsToLoad {
		// If there isn't any used version, or used version is too old, we do full load.
		return false, nil
	}
	if usedVersion > newVersion {
		// When user use History Read feature, history schema will be loaded.
		// usedVersion may be larger than newVersion, full load is needed.
		return false, nil
	}
	var diffs []*model.SchemaDiff
	for usedVersion < newVersion {
		usedVersion++
		diff, err := m.GetSchemaDiff(usedVersion)
		if err != nil {
			return false, errors.Trace(err)
		}
		if diff == nil {
			// If diff is missing for any version between used and new version, we fall back to full reload.
			return false, nil
		}
		diffs = append(diffs, diff)
	}
	builder := infoschema.NewBuilder(do.infoHandle).InitWithOldInfoSchema()
	for _, diff := range diffs {
		err := builder.ApplyDiff(m, diff)
		if err != nil {
			return false, errors.Trace(err)
		}
	}
	builder.Build()
	return true, nil
}