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from sqlalchemy import sql, util, schema, topological
"""utility functions that build upon SQL and Schema constructs"""
class TableCollection(object):
def __init__(self, tables=None):
self.tables = tables or []
def __len__(self):
return len(self.tables)
def __getitem__(self, i):
return self.tables[i]
def __iter__(self):
return iter(self.tables)
def __contains__(self, obj):
return obj in self.tables
def __add__(self, obj):
return self.tables + list(obj)
def add(self, table):
self.tables.append(table)
if hasattr(self, '_sorted'):
del self._sorted
def sort(self, reverse=False):
try:
sorted = self._sorted
except AttributeError, e:
self._sorted = self._do_sort()
sorted = self._sorted
if reverse:
x = sorted[:]
x.reverse()
return x
else:
return sorted
def _do_sort(self):
tuples = []
class TVisitor(schema.SchemaVisitor):
def visit_foreign_key(_self, fkey):
if fkey.use_alter:
return
parent_table = fkey.column.table
if parent_table in self:
child_table = fkey.parent.table
tuples.append( ( parent_table, child_table ) )
vis = TVisitor()
for table in self.tables:
table.accept_schema_visitor(vis)
sorter = topological.QueueDependencySorter( tuples, self.tables )
head = sorter.sort()
sequence = []
def to_sequence( node, seq=sequence):
seq.append( node.item )
for child in node.children:
to_sequence( child )
if head is not None:
to_sequence( head )
return sequence
class TableFinder(TableCollection, sql.ClauseVisitor):
"""given a Clause, locates all the Tables within it into a list."""
def __init__(self, table, check_columns=False):
TableCollection.__init__(self)
self.check_columns = check_columns
if table is not None:
table.accept_visitor(self)
def visit_table(self, table):
self.tables.append(table)
def visit_column(self, column):
if self.check_columns:
column.table.accept_visitor(self)
class ColumnFinder(sql.ClauseVisitor):
def __init__(self):
self.columns = util.Set()
def visit_column(self, c):
self.columns.add(c)
def __iter__(self):
return iter(self.columns)
class Aliasizer(sql.ClauseVisitor):
"""converts a table instance within an expression to be an alias of that table."""
def __init__(self, *tables, **kwargs):
self.tables = {}
self.aliases = kwargs.get('aliases', {})
for t in tables:
self.tables[t] = t
if not self.aliases.has_key(t):
self.aliases[t] = sql.alias(t)
if isinstance(t, sql.Join):
for t2 in t.columns:
self.tables[t2.table] = t2
self.aliases[t2.table] = self.aliases[t]
self.binary = None
def get_alias(self, table):
return self.aliases[table]
def visit_compound(self, compound):
self.visit_clauselist(compound)
def visit_clauselist(self, clist):
for i in range(0, len(clist.clauses)):
if isinstance(clist.clauses[i], schema.Column) and self.tables.has_key(clist.clauses[i].table):
orig = clist.clauses[i]
clist.clauses[i] = self.get_alias(clist.clauses[i].table).corresponding_column(clist.clauses[i])
def visit_binary(self, binary):
if isinstance(binary.left, schema.Column) and self.tables.has_key(binary.left.table):
binary.left = self.get_alias(binary.left.table).corresponding_column(binary.left)
if isinstance(binary.right, schema.Column) and self.tables.has_key(binary.right.table):
binary.right = self.get_alias(binary.right.table).corresponding_column(binary.right)
class ClauseAdapter(sql.ClauseVisitor):
"""given a clause (like as in a WHERE criterion), locates columns which 'correspond' to a given selectable,
and changes those columns to be that of the selectable.
such as:
table1 = Table('sometable', metadata,
Column('col1', Integer),
Column('col2', Integer)
)
table2 = Table('someothertable', metadata,
Column('col1', Integer),
Column('col2', Integer)
)
condition = table1.c.col1 == table2.c.col1
and make an alias of table1:
s = table1.alias('foo')
calling condition.accept_visitor(ClauseAdapter(s)) converts condition to read:
s.c.col1 == table2.c.col1
"""
def __init__(self, selectable):
self.selectable = selectable
def visit_binary(self, binary):
if isinstance(binary.left, sql.ColumnElement):
col = self.selectable.corresponding_column(binary.left, raiseerr=False, keys_ok=True)
if col is not None:
binary.left = col
if isinstance(binary.right, sql.ColumnElement):
col = self.selectable.corresponding_column(binary.right, raiseerr=False, keys_ok=True)
if col is not None:
binary.right = col
class ColumnsInClause(sql.ClauseVisitor):
"""given a selectable, visits clauses and determines if any columns from the clause are in the selectable"""
def __init__(self, selectable):
self.selectable = selectable
self.result = False
def visit_column(self, column):
if self.selectable.c.get(column.key) is column:
self.result = True
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