public override void Perform(SchemaChanges changes, IOutput output)
{
foreach (var pending in PendingReorderTableType.AllFrom(changes.Current))
{
var originalTable = TableType.Identifier(pending.Name);
var tempTable = pending.ParentIdentifier;
if (object.Equals(originalTable, tempTable))
{
// If the database fails at precisely the wrong time, the rename can be succeed without dropping the PendingReorder,
// so the table thinks it's to be renamed to itself. In that case we need to drop the PendingReorder, NOT drop the table!
output.Verbose("Cleaning up after completed reorder of columns in " + originalTable);
changes.Remove(null, pending);
}
else if (changes.Current.ContainsRoot(originalTable))
{
// If the original table still exists, we drop the temp table so we can start over (in case the data in the table has changed since the temp table
// was created, or the reordering has somehow become unnecessary).
output.Verbose("Clearing pending reorder of columns in " + originalTable);
changes.Remove(changes.SchemaDriver.GetDropTableSql(pending.ParentName), changes.Current.GetRoot(pending.ParentIdentifier));
}
else
{
// The original table has been dropped so we need to recreate it by renaming the temp table.
output.Verbose("Completing pending reordering of columns in " + originalTable);
changes.Rename(changes.SchemaDriver.GetRenameTableSql(tempTable.Name, originalTable.Name), tempTable, originalTable);
// And forget about the pending rename.
changes.Remove(null, pending.WithParent(originalTable));
}
}
}
private void renameTempTables(SchemaChanges changes, IOutput output)
{
// For any PendingReorderTables where the original table doesn't exist, rename the table to the target name and remove the pending rename.
foreach (var pending in PendingReorderTableType.AllFrom(changes.Current))
{
var originalTable = TableType.Identifier(pending.Name);
var tempTable = pending.ParentIdentifier;
if (changes.Current.ContainsRoot(originalTable))
{
continue;
}
changes.Rename(changes.SchemaDriver.GetRenameTableSql(tempTable.Name, originalTable.Name), tempTable, originalTable);
changes.Remove(null, pending.WithParent(originalTable));
}
}
private void dropOriginalTables(SchemaChanges changes, IOutput output)
{
// For any tables that are the target of existing PendingReorderTables, drop them (without prompting).
foreach (var pending in PendingReorderTableType.AllFrom(changes.Current))
{
var originalTable = TableType.Identifier(pending.Name);
var tempTable = pending.ParentIdentifier;
if (!changes.Current.ContainsRoot(originalTable))
{
continue;
}
// FIXME: (Consider sanity checks before doing this - anything from "confirm all the right column names exist" to "confirm the right number of rows exist" to
// "confirm all the data is identical in all the rows")
changes.Remove(changes.SchemaDriver.GetDropTableSql(originalTable.Name), changes.Current.GetRoot(originalTable));
}
}
public override void Perform(SchemaChanges changes, IOutput output)
{
var pendingReorders = PendingReorderTableType.AllFrom(changes.Current);
foreach (var desired in TableType.AllFrom(changes.Desired))
{
if (changes.Current.Contains(desired))
{
continue;
}
var fields = FieldType.ChildrenFrom(changes.Desired, desired.Identifier);
var fieldCreation = from field in fields
orderby field.State.OrdinalPosition
select new FieldCreation(field.Name, field.State.DataType, field.State.IsNullable, field.State.IsSequencedPkey, field.State.SequenceName);
changes.Put(changes.SchemaDriver.GetCreateTableSql(desired.Name, fieldCreation),
new ObjectState[] { desired }.Concat(fields));
}
}
private void createTempTables(SchemaChanges changes, IOutput output)
{
// For any tables with order-sensitivity and fields in different order between current and desired (ignoring fields that only exist in current),
// Create a new table "_nrdo_reorder" using "select (columns in correct order followed by columns to be dropped) from original table into newname"
// Put the table, the fields (with nullability, datatype and identityness as current but in new order) and a PendingReorderTable into current
// For any tables that need their fields reordered, create a copy of the table with the fields in the right order.
foreach (var origTable in TableType.AllFrom(changes.Current))
{
// Tables that don't exist in desired state are to be dropped, they certainly don't need to be reordered!
if (!changes.Desired.Contains(origTable))
{
continue;
}
// Figure out whether a reorder is needed
if (!FieldType.IsFieldReorderNeeded(changes, origTable.Identifier))
{
continue;
}
// Put the fields in order.
// At this point there may be extra fields that are to be dropped but haven't been yet. They need to stick around until
// it's time to drop them, because before statements may rely on them. But we put those ones last (in the order they're currently in).
var fieldsInOrder = from field in FieldType.ChildrenFrom(changes.Current, origTable.Identifier)
let desired = changes.Desired.Get(field)
orderby
desired != null ? desired.State.OrdinalPosition : int.MaxValue,
field.State.OrdinalPosition
select field;
// Construct the state representation that will be used for the new table.
// It inherits all before statements from the original table so that when it's renamed they'll still be there.
// FIXME: This hardcodes the assumption that CreateTableAsSelect preserves field type, nullability and identity-ness, which may or may not be true on other DBs
// FIXME: any other aspects of field state that we add support for (Default values, check constraints...) need to get dropped here.
var tempTable = TableType.Create(origTable.Name + "_nrdo_reorder");
var pendingReorder = PendingReorderTableType.Create(tempTable.Identifier, origTable.Name);
var tempTableFields = from fi in fieldsInOrder.Select((field, index) => new { field, index })
select fi.field
.WithParent(tempTable.Identifier)
.With(s => s.WithOrdinalPosition(fi.index));
var tempTableBefores = from before in BeforeStatementType.ChildrenFrom(changes.Current, origTable.Identifier)
select before.WithParent(tempTable.Identifier);
// Gather all temporary objects into one list to put them into the database together
var tempTableObjects =
new ObjectState[]
{
tempTable,
pendingReorder
}
.Concat(tempTableFields)
.Concat(tempTableBefores);
var sql = changes.SchemaDriver.GetCreateTableAsSelectSql(tempTable.Name,
string.Join(", ", from field in fieldsInOrder select changes.DbDriver.QuoteIdentifier(field.Name)),
changes.DbDriver.QuoteSchemaIdentifier(origTable.Name));
changes.Put(sql, tempTableObjects);
}
}