def test_subtree(self):
"""test subtree generation from get_smallest_subtree"""
schema = (
(1, 2), # 0->1,2
(3, ), # 1->3
(),
()
)
construct_query = ConstructQuery(schema)
res = construct_query.get_smallest_subtree((0, 3))
# print "subtree 0 3", res
#self.assertEqual(res, RootedGraph())
res = construct_query.get_smallest_subtree((3, 1, 0))
# print "subtree 0 1 3", res
#self.listTest(res, ((1,0), (3,1)))
res = construct_query.get_smallest_subtree((0, 2))
# print "subtree 0 2", res
#self.listTest(res, ((2,0),))
res = construct_query.get_smallest_subtree((0, ))
class Schema(object):
"""
This object is created around a sqlalchemy MetaData object. When given
a sqlalchemy select object in build_query, it constructs determines how to
join tables from the MetaData to support the query.
"""
def __init__(self, tables, foreign_keys = None, owner = None):
"""
Constructor
"""
class MySchema(object):
"""class encapsulate tables structure"""
def __init__(self, tables):
"""initialize tables"""
self.tables = tables
# The dictionary keys disagree with table names. Make them agree.
table_dict = {}
for table_name in tables:
table = tables[table_name]
table_dict[table.name] = table
self._schema = MySchema(table_dict)
self._ordered = None
person_table = 'person'
if owner:
self._owner = owner.lower()
else:
self._owner = owner
self._foreign_tables = {}
self._person_table = find_table(self._schema, person_table)
if self._person_table:
to_exclude = set([self._person_table])
else:
to_exclude = set()
connectivity = self.graph_from_schema(self._schema,
self.make_foreign_keys(foreign_keys, self._schema), to_exclude)
self.construct_query = ConstructQuery(connectivity)
self.outers = [('seblock.blockid', 'block.id'),
('block.id', 'seblock.blockid')]
def build_query(self, query):
"""build query by root_join"""
root_join = self.root_join(query)
if query != root_join:
query.append_from(root_join)
return query
def build_query_with_sel(self, sel, query, add_join = None):
"""extral root_join.join with add_join """
root_join = self.root_join(query)
if add_join:
for item in add_join:
table, l_col, r_col = item
root_join = root_join.join(table, l_col == r_col)
sel.append_from(root_join)
return sel
def root_join(self, query):
'''
Query is a sqlalchemy query with select elements and where clauses.
This method:
- looks through the elements and clauses to determine
which tables need to be joined in order to support the query.
- adds those joins to the query and returns it.
'''
tables_of_concern = set()
# col.table returns a select statement. We want the metadata table.
# This is unsupported in sqlalchemy!
# Todo I need verify this.
# for col in query._raw_columns:
# tables_of_concern.add(col.table)
for table in query.froms:
tables_of_concern.add(table)
if query.__dict__.has_key('whereclause'): # SQLAlchemy 0.3
where_clause = query.whereclause
elif query.__dict__.has_key('_whereclause'): # SQLAlchemy 0.4 0.5
where_clause = query._whereclause
else:
raise Exception, "Query '%s' does not contain whereclause" % query
if where_clause:
if where_clause.__dict__.has_key('clauses'):
for clause in where_clause.clauses:
pull_operator_side(clause, tables_of_concern)
else:
pull_operator_side(where_clause , tables_of_concern)
# No need to calculate joins if there is only one table involved.
# We actually make mistakes if that single table is Person.
if len(tables_of_concern) == 1:
return query
# Remove Person table because it is not in any spanning trees.
block_use_person_table = False
if self._person_table in tables_of_concern:
tables_of_concern.remove(self._person_table)
block_use_person_table = True
# Find the smallest spanning tree containing tables
# for SELECT and WHERE.
# table_indices is the index list of table not concerns
# references to self._ordered
table_indices = [self._ordered.index(table)
for table in tables_of_concern]
subtree = self.construct_query.get_smallest_subtree(table_indices)
if subtree is None:
return None
_LOGGER.debug("Schema.build_query: query tree length %d" %
(subtree.get_nodes_number(), ))
_LOGGER.debug("Schema.build_query: query tree itself %s" %
(subtree, ))
# The subtree tells us the order of tables in the join, but it loses
# information on which table is the foreign key, so we need to search
# through tables to find which had the foreign key and which the
# primary key.
# root_join is a table.join().join()....
root_join = None
for (node_idx, parent_idx) in subtree.breadth_first():
if parent_idx is None:
root_table = self._ordered[node_idx]
root_join = root_table
if block_use_person_table and root_table.c.has_key('CreatedBy'):
root_join = root_join.join(self._person_table,
root_table.c.CreatedBy == self._person_table.c.ID)
else:
if node_idx in self._foreign_tables[parent_idx]:
# table has a f_key to parent
(l_col, r_col) = self._foreign_tables[parent_idx][node_idx]
elif parent_idx in self._foreign_tables[node_idx]:
# parent table has a f_key to this table
(r_col, l_col) = self._foreign_tables[node_idx][parent_idx]
# special case:
# block to seblock == 1 we outerjoin seblock
# seblock to block == 0 we join block, block table is huge
if self.outers.count((str(l_col).lower(), str(r_col).lower())):
root_join = root_join.outerjoin(r_col.table, l_col == r_col)
else:
root_join = root_join.join(r_col.table, l_col == r_col)
# root_join = root_join.join(r_col.table, l_col==r_col)
return root_join
# query.append_from(root_join)
# return query
def make_foreign_keys(self, foreign_keys, schema):
""" input: foreign_keys and schema
output: foreign_keys
when input foreign_keys not exists, it is generated from schema by
{ table:table.foreign_keys, ...}
"""
if not foreign_keys:
foreign_keys = {}
for table_name in schema.tables:
table = schema.tables[table_name]
foreign_keys[table] = table.foreign_keys
return foreign_keys
def graph_from_schema(self, metadata, table_fks, exclude = set()):
"""
Build graph with edges for provided SQLAlchemy MetaDta object;
list of foreign keys and set of exclude tables.
"""
#_ordered is a list version of metadata.tables.values()
# and we can set exclude table list
self._ordered = [metadata.tables[table_name]
for table_name in metadata.tables
if metadata.tables[table_name] not in exclude]
# contains all foreign keys linked table index in ordered_names
relations = []
# ordered_names which is the list version of fullname self._ordered
# VK, use names rather then compare tables objects
ordered_names = []
for item in self._ordered:
# ordered_names.append(item.fullname)
ordered_names.append(item.name)
exclude_names_list = []
for table in exclude:
# exclude_names_list.append(table.fullname)
exclude_names_list.append(table.name)
exclude_names = set(exclude_names_list) # set of exclude table name
order_list = list(ordered_names) # list of table_name in _ordered
order_list.sort()
# print "\n\nSchema:"
# print order_list
# print exclude_names
# print "owner",self._owner
try:
search_name = None
# traversing the tables
# for each foreign_keys in this table:
# find correspond table index in ordered_names(self._ordered)
# relations store set of thoses f_key_index
# self._foreign_tables[table_index] store {f_key_index:FK, ...}
for table_index in xrange(0, len(self._ordered)):
table = self._ordered[table_index]
foreign_keys = table_fks[table]
index_set = set()
short_tables = {}
for f_key in foreign_keys:
if f_key.column.table in exclude:
# table linked by foreign keys not in exclude list
continue
search_name = f_key.column.table
if search_name.name in exclude_names:
# table.fullname are not in exclude list
continue
# f_key_index = self._ordered.index(search_name)
f_key_index = ordered_names.index(search_name.name)
index_set.add(f_key_index)
short_tables[f_key_index] = (f_key.parent, f_key.column)
relations.append(index_set)
self._foreign_tables[table_index] = short_tables
# foreign_tables stores
# {table_index:{f_key_index:(f_key.parent,f_key.colum),...},...}
except ValueError, value_err:
print value_err
_LOGGER.error("""Schema.GraphFromSchema ValueError %s.
Could not find f_key.column.table %s in
self._ordered %s. Len(ordered)=%d
Len(metadata.tables)=%d""" % (str(value_err),
search_name, self._ordered, len(self._ordered),
len(metadata.tables)))
raise Exception(
"Could not find the table for a given foreign key constraint.",
'''Constraint table %s len(ordered)=%d len(metadata.tables)=%d
ordered=%s''' % (search_name, len(self._ordered),
len(metadata.tables), str([xdx.name for xdx in self._ordered])))
return relations