/
introspection.py
269 lines (239 loc) · 11 KB
/
introspection.py
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import re
from django.db.backends.base.introspection import (
BaseDatabaseIntrospection, FieldInfo, TableInfo,
)
from django.db.models.indexes import Index
field_size_re = re.compile(r'^\s*(?:var)?char\s*\(\s*(\d+)\s*\)\s*$')
def get_field_size(name):
""" Extract the size number from a "varchar(11)" type name """
m = field_size_re.search(name)
return int(m.group(1)) if m else None
# This light wrapper "fakes" a dictionary interface, because some SQLite data
# types include variables in them -- e.g. "varchar(30)" -- and can't be matched
# as a simple dictionary lookup.
class FlexibleFieldLookupDict:
# Maps SQL types to Django Field types. Some of the SQL types have multiple
# entries here because SQLite allows for anything and doesn't normalize the
# field type; it uses whatever was given.
base_data_types_reverse = {
'bool': 'BooleanField',
'boolean': 'BooleanField',
'smallint': 'SmallIntegerField',
'smallint unsigned': 'PositiveSmallIntegerField',
'smallinteger': 'SmallIntegerField',
'int': 'IntegerField',
'integer': 'IntegerField',
'bigint': 'BigIntegerField',
'integer unsigned': 'PositiveIntegerField',
'decimal': 'DecimalField',
'real': 'FloatField',
'text': 'TextField',
'char': 'CharField',
'blob': 'BinaryField',
'date': 'DateField',
'datetime': 'DateTimeField',
'time': 'TimeField',
}
def __getitem__(self, key):
key = key.lower()
try:
return self.base_data_types_reverse[key]
except KeyError:
size = get_field_size(key)
if size is not None:
return ('CharField', {'max_length': size})
raise KeyError
class DatabaseIntrospection(BaseDatabaseIntrospection):
data_types_reverse = FlexibleFieldLookupDict()
def get_table_list(self, cursor):
"""Return a list of table and view names in the current database."""
# Skip the sqlite_sequence system table used for autoincrement key
# generation.
cursor.execute("""
SELECT name, type FROM sqlite_master
WHERE type in ('table', 'view') AND NOT name='sqlite_sequence'
ORDER BY name""")
return [TableInfo(row[0], row[1][0]) for row in cursor.fetchall()]
def get_table_description(self, cursor, table_name):
"""
Return a description of the table with the DB-API cursor.description
interface.
"""
return [
FieldInfo(
info['name'],
info['type'],
None,
info['size'],
None,
None,
info['null_ok'],
info['default'],
) for info in self._table_info(cursor, table_name)
]
def get_sequences(self, cursor, table_name, table_fields=()):
pk_col = self.get_primary_key_column(cursor, table_name)
return [{'table': table_name, 'column': pk_col}]
def get_relations(self, cursor, table_name):
"""
Return a dictionary of {field_name: (field_name_other_table, other_table)}
representing all relationships to the given table.
"""
# Dictionary of relations to return
relations = {}
# Schema for this table
cursor.execute("SELECT sql FROM sqlite_master WHERE tbl_name = %s AND type = %s", [table_name, "table"])
try:
results = cursor.fetchone()[0].strip()
except TypeError:
# It might be a view, then no results will be returned
return relations
results = results[results.index('(') + 1:results.rindex(')')]
# Walk through and look for references to other tables. SQLite doesn't
# really have enforced references, but since it echoes out the SQL used
# to create the table we can look for REFERENCES statements used there.
for field_desc in results.split(','):
field_desc = field_desc.strip()
if field_desc.startswith("UNIQUE"):
continue
m = re.search(r'references (\S*) ?\(["|]?(.*)["|]?\)', field_desc, re.I)
if not m:
continue
table, column = [s.strip('"') for s in m.groups()]
if field_desc.startswith("FOREIGN KEY"):
# Find name of the target FK field
m = re.match(r'FOREIGN KEY\s*\(([^\)]*)\).*', field_desc, re.I)
field_name = m.groups()[0].strip('"')
else:
field_name = field_desc.split()[0].strip('"')
cursor.execute("SELECT sql FROM sqlite_master WHERE tbl_name = %s", [table])
result = cursor.fetchall()[0]
other_table_results = result[0].strip()
li, ri = other_table_results.index('('), other_table_results.rindex(')')
other_table_results = other_table_results[li + 1:ri]
for other_desc in other_table_results.split(','):
other_desc = other_desc.strip()
if other_desc.startswith('UNIQUE'):
continue
other_name = other_desc.split(' ', 1)[0].strip('"')
if other_name == column:
relations[field_name] = (other_name, table)
break
return relations
def get_key_columns(self, cursor, table_name):
"""
Return a list of (column_name, referenced_table_name, referenced_column_name)
for all key columns in given table.
"""
key_columns = []
# Schema for this table
cursor.execute("SELECT sql FROM sqlite_master WHERE tbl_name = %s AND type = %s", [table_name, "table"])
results = cursor.fetchone()[0].strip()
results = results[results.index('(') + 1:results.rindex(')')]
# Walk through and look for references to other tables. SQLite doesn't
# really have enforced references, but since it echoes out the SQL used
# to create the table we can look for REFERENCES statements used there.
for field_index, field_desc in enumerate(results.split(',')):
field_desc = field_desc.strip()
if field_desc.startswith("UNIQUE"):
continue
m = re.search(r'"(.*)".*references (.*) \(["|](.*)["|]\)', field_desc, re.I)
if not m:
continue
# This will append (column_name, referenced_table_name, referenced_column_name) to key_columns
key_columns.append(tuple(s.strip('"') for s in m.groups()))
return key_columns
def get_primary_key_column(self, cursor, table_name):
"""Return the column name of the primary key for the given table."""
# Don't use PRAGMA because that causes issues with some transactions
cursor.execute("SELECT sql FROM sqlite_master WHERE tbl_name = %s AND type = %s", [table_name, "table"])
row = cursor.fetchone()
if row is None:
raise ValueError("Table %s does not exist" % table_name)
results = row[0].strip()
results = results[results.index('(') + 1:results.rindex(')')]
for field_desc in results.split(','):
field_desc = field_desc.strip()
m = re.search('"(.*)".*PRIMARY KEY( AUTOINCREMENT)?', field_desc)
if m:
return m.groups()[0]
return None
def _table_info(self, cursor, name):
cursor.execute('PRAGMA table_info(%s)' % self.connection.ops.quote_name(name))
# cid, name, type, notnull, default_value, pk
return [{
'name': field[1],
'type': field[2],
'size': get_field_size(field[2]),
'null_ok': not field[3],
'default': field[4],
'pk': field[5], # undocumented
} for field in cursor.fetchall()]
def get_constraints(self, cursor, table_name):
"""
Retrieve any constraints or keys (unique, pk, fk, check, index) across
one or more columns.
"""
constraints = {}
# Get the index info
cursor.execute("PRAGMA index_list(%s)" % self.connection.ops.quote_name(table_name))
for row in cursor.fetchall():
# Sqlite3 3.8.9+ has 5 columns, however older versions only give 3
# columns. Discard last 2 columns if there.
number, index, unique = row[:3]
# Get the index info for that index
cursor.execute('PRAGMA index_info(%s)' % self.connection.ops.quote_name(index))
for index_rank, column_rank, column in cursor.fetchall():
if index not in constraints:
constraints[index] = {
"columns": [],
"primary_key": False,
"unique": bool(unique),
"foreign_key": False,
"check": False,
"index": True,
}
constraints[index]['columns'].append(column)
# Add type and column orders for indexes
if constraints[index]['index'] and not constraints[index]['unique']:
# SQLite doesn't support any index type other than b-tree
constraints[index]['type'] = Index.suffix
cursor.execute(
"SELECT sql FROM sqlite_master "
"WHERE type='index' AND name=%s" % self.connection.ops.quote_name(index)
)
orders = []
# There would be only 1 row to loop over
for sql, in cursor.fetchall():
order_info = sql.split('(')[-1].split(')')[0].split(',')
orders = ['DESC' if info.endswith('DESC') else 'ASC' for info in order_info]
constraints[index]['orders'] = orders
# Get the PK
pk_column = self.get_primary_key_column(cursor, table_name)
if pk_column:
# SQLite doesn't actually give a name to the PK constraint,
# so we invent one. This is fine, as the SQLite backend never
# deletes PK constraints by name, as you can't delete constraints
# in SQLite; we remake the table with a new PK instead.
constraints["__primary__"] = {
"columns": [pk_column],
"primary_key": True,
"unique": False, # It's not actually a unique constraint.
"foreign_key": False,
"check": False,
"index": False,
}
# Get foreign keys
cursor.execute('PRAGMA foreign_key_list(%s)' % self.connection.ops.quote_name(table_name))
for row in cursor.fetchall():
# Remaining on_update/on_delete/match values are of no interest here
id_, seq, table, from_, to = row[:5]
constraints['fk_%d' % id_] = {
'columns': [from_],
'primary_key': False,
'unique': False,
'foreign_key': (table, to),
'check': False,
'index': False,
}
return constraints