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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:
vis.traverse(table)
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.NoColumnVisitor):
"""locate all Tables within a clause."""
def __init__(self, table, check_columns=False, include_aliases=False):
TableCollection.__init__(self)
self.check_columns = check_columns
self.include_aliases = include_aliases
if table is not None:
self.traverse(table)
def visit_alias(self, alias):
if self.include_aliases:
self.tables.append(alias)
def visit_table(self, table):
self.tables.append(table)
def visit_column(self, column):
if self.check_columns:
self.traverse(column.table)
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 ColumnsInClause(sql.ClauseVisitor):
"""Given a selectable, visit clauses and determine 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
class AbstractClauseProcessor(sql.NoColumnVisitor):
"""Traverse a clause and attempt to convert the contents of container elements
to a converted element.
The conversion operation is defined by subclasses.
"""
def convert_element(self, elem):
"""Define the *conversion* method for this ``AbstractClauseProcessor``."""
raise NotImplementedError()
def copy_and_process(self, list_):
"""Copy the container elements in the given list to a new list and
process the new list.
"""
list_ = [o.copy_container() for o in list_]
self.process_list(list_)
return list_
def process_list(self, list_):
"""Process all elements of the given list in-place."""
for i in range(0, len(list_)):
elem = self.convert_element(list_[i])
if elem is not None:
list_[i] = elem
else:
self.traverse(list_[i])
def visit_grouping(self, grouping):
elem = self.convert_element(grouping.elem)
if elem is not None:
grouping.elem = elem
def visit_clauselist(self, clist):
for i in range(0, len(clist.clauses)):
n = self.convert_element(clist.clauses[i])
if n is not None:
clist.clauses[i] = n
def visit_unary(self, unary):
elem = self.convert_element(unary.element)
if elem is not None:
unary.element = elem
def visit_binary(self, binary):
elem = self.convert_element(binary.left)
if elem is not None:
binary.left = elem
elem = self.convert_element(binary.right)
if elem is not None:
binary.right = elem
# TODO: visit_select().
class ClauseAdapter(AbstractClauseProcessor):
"""Given a clause (like as in a WHERE criterion), locate columns
which are embedded within a given selectable, and changes those
columns to be that of the selectable.
E.g.::
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 ``ClauseAdapter(s).traverse(condition)`` converts
condition to read::
s.c.col1 == table2.c.col1
"""
def __init__(self, selectable, include=None, exclude=None, equivalents=None):
self.selectable = selectable
self.include = include
self.exclude = exclude
self.equivalents = equivalents
def convert_element(self, col):
if not isinstance(col, sql.ColumnElement):
return None
if self.include is not None:
if col not in self.include:
return None
if self.exclude is not None:
if col in self.exclude:
return None
newcol = self.selectable.corresponding_column(col, raiseerr=False, require_embedded=True, keys_ok=False)
if newcol is None and self.equivalents is not None and col in self.equivalents:
for equiv in self.equivalents[col]:
newcol = self.selectable.corresponding_column(equiv, raiseerr=False, require_embedded=True, keys_ok=False)
if newcol:
return newcol
return newcol
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