veekun_pokedex/pokedex/db/dependencies.py

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import sqlalchemy.sql.visitors as visitors
from pokedex.db.tables import metadata
# stolen from sqlalchemy.sql.util.sort_tables
def compute_dependencies(tables):
"""Construct a reverse dependency graph for the given tables.
Returns a dict which maps a table to the list of tables which depend on it.
"""
tables = list(tables)
graph = {}
def visit_foreign_key(fkey):
if fkey.use_alter:
return
parent_table = fkey.column.table
if parent_table in tables:
child_table = fkey.parent.table
if parent_table is not child_table:
graph.setdefault(parent_table, []).append(child_table)
for table in tables:
visitors.traverse(table,
{'schema_visitor': True},
{'foreign_key': visit_foreign_key})
graph.setdefault(table, []).extend(table._extra_dependencies)
return graph
#: The dependency graph for pokedex.db.tables
_pokedex_graph = compute_dependencies(metadata.tables.values())
def find_dependent_tables(tables, graph=None):
"""Recursively find all tables which depend on the given tables.
The returned set does not include the original tables.
"""
if graph is None:
graph = _pokedex_graph
tables = list(tables)
dependents = set()
def add_dependents_of(table):
for dependent_table in graph.get(table, []):
if dependent_table not in dependents:
dependents.add(dependent_table)
add_dependents_of(dependent_table)
for table in tables:
add_dependents_of(table)
dependents -= set(tables)
return dependents