app/django/db/backends/postgresql/operations.py
author Todd Larsen <tlarsen@google.com>
Fri, 18 Jul 2008 18:22:23 +0000
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child 323 ff1a9aa48cfd
permissions -rw-r--r--
Major reorganization of the soc svn repo, to merge into a single App Engine image (to make development easier, now that only a single app will run all Google Open Source programs).
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import re
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from django.db.backends import BaseDatabaseOperations
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server_version_re = re.compile(r'PostgreSQL (\d{1,2})\.(\d{1,2})\.?(\d{1,2})?')
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# This DatabaseOperations class lives in here instead of base.py because it's
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# used by both the 'postgresql' and 'postgresql_psycopg2' backends.
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class DatabaseOperations(BaseDatabaseOperations):
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    def __init__(self):
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        self._postgres_version = None
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    def _get_postgres_version(self):
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        if self._postgres_version is None:
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            from django.db import connection
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            cursor = connection.cursor()
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            cursor.execute("SELECT version()")
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            version_string = cursor.fetchone()[0]
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            m = server_version_re.match(version_string)
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            if not m:
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                raise Exception('Unable to determine PostgreSQL version from version() function string: %r' % version_string)
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            self._postgres_version = [int(val) for val in m.groups() if val]
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        return self._postgres_version
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    postgres_version = property(_get_postgres_version)
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    def date_extract_sql(self, lookup_type, field_name):
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        # http://www.postgresql.org/docs/8.0/static/functions-datetime.html#FUNCTIONS-DATETIME-EXTRACT
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        return "EXTRACT('%s' FROM %s)" % (lookup_type, field_name)
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    def date_trunc_sql(self, lookup_type, field_name):
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        # http://www.postgresql.org/docs/8.0/static/functions-datetime.html#FUNCTIONS-DATETIME-TRUNC
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        return "DATE_TRUNC('%s', %s)" % (lookup_type, field_name)
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    def deferrable_sql(self):
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        return " DEFERRABLE INITIALLY DEFERRED"
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    def field_cast_sql(self, db_type):
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        if db_type == 'inet':
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            return 'HOST(%s)'
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        return '%s'
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    def last_insert_id(self, cursor, table_name, pk_name):
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        cursor.execute("SELECT CURRVAL('\"%s_%s_seq\"')" % (table_name, pk_name))
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        return cursor.fetchone()[0]
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    def no_limit_value(self):
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        return None
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    def quote_name(self, name):
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        if name.startswith('"') and name.endswith('"'):
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            return name # Quoting once is enough.
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        return '"%s"' % name
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    def sql_flush(self, style, tables, sequences):
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        if tables:
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            if self.postgres_version[0] >= 8 and self.postgres_version[1] >= 1:
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                # Postgres 8.1+ can do 'TRUNCATE x, y, z...;'. In fact, it *has to*
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                # in order to be able to truncate tables referenced by a foreign
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                # key in any other table. The result is a single SQL TRUNCATE
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                # statement.
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                sql = ['%s %s;' % \
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                    (style.SQL_KEYWORD('TRUNCATE'),
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                     style.SQL_FIELD(', '.join([self.quote_name(table) for table in tables]))
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                )]
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            else:
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                # Older versions of Postgres can't do TRUNCATE in a single call, so
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                # they must use a simple delete.
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                sql = ['%s %s %s;' % \
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                        (style.SQL_KEYWORD('DELETE'),
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                         style.SQL_KEYWORD('FROM'),
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                         style.SQL_FIELD(self.quote_name(table))
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                         ) for table in tables]
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            # 'ALTER SEQUENCE sequence_name RESTART WITH 1;'... style SQL statements
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            # to reset sequence indices
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            for sequence_info in sequences:
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                table_name = sequence_info['table']
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                column_name = sequence_info['column']
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                if column_name and len(column_name) > 0:
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                    sequence_name = '%s_%s_seq' % (table_name, column_name)
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                else:
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                    sequence_name = '%s_id_seq' % table_name
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                sql.append("%s setval('%s', 1, false);" % \
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                    (style.SQL_KEYWORD('SELECT'),
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                    style.SQL_FIELD(self.quote_name(sequence_name)))
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                )
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            return sql
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        else:
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            return []
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    def sequence_reset_sql(self, style, model_list):
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        from django.db import models
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        output = []
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        qn = self.quote_name
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        for model in model_list:
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            # Use `coalesce` to set the sequence for each model to the max pk value if there are records,
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            # or 1 if there are none. Set the `is_called` property (the third argument to `setval`) to true
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            # if there are records (as the max pk value is already in use), otherwise set it to false.
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            for f in model._meta.fields:
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                if isinstance(f, models.AutoField):
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                    output.append("%s setval('%s', coalesce(max(%s), 1), max(%s) %s null) %s %s;" % \
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                        (style.SQL_KEYWORD('SELECT'),
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                        style.SQL_FIELD(qn('%s_%s_seq' % (model._meta.db_table, f.column))),
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                        style.SQL_FIELD(qn(f.column)),
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                        style.SQL_FIELD(qn(f.column)),
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                        style.SQL_KEYWORD('IS NOT'),
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                        style.SQL_KEYWORD('FROM'),
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                        style.SQL_TABLE(qn(model._meta.db_table))))
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                    break # Only one AutoField is allowed per model, so don't bother continuing.
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            for f in model._meta.many_to_many:
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                output.append("%s setval('%s', coalesce(max(%s), 1), max(%s) %s null) %s %s;" % \
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                    (style.SQL_KEYWORD('SELECT'),
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                    style.SQL_FIELD(qn('%s_id_seq' % f.m2m_db_table())),
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                    style.SQL_FIELD(qn('id')),
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                    style.SQL_FIELD(qn('id')),
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                    style.SQL_KEYWORD('IS NOT'),
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                    style.SQL_KEYWORD('FROM'),
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                    style.SQL_TABLE(qn(f.m2m_db_table()))))
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        return output