from django.db.models.sql import compiler
class SQLCompiler(compiler.SQLCompiler):
def resolve_columns(self, row, fields=()):
# If this query has limit/offset information, then we expect the
# first column to be an extra "_RN" column that we need to throw
# away.
if self.query.high_mark is not None or self.query.low_mark:
rn_offset = 1
else:
rn_offset = 0
index_start = rn_offset + len(self.query.extra_select.keys())
values = [self.query.convert_values(v, None, connection=self.connection)
for v in row[rn_offset:index_start]]
for value, field in map(None, row[index_start:], fields):
values.append(self.query.convert_values(value, field, connection=self.connection))
return tuple(values)
def as_sql(self, with_limits=True, with_col_aliases=False):
"""
Creates the SQL for this query. Returns the SQL string and list
of parameters. This is overriden from the original Query class
to handle the additional SQL Oracle requires to emulate LIMIT
and OFFSET.
If 'with_limits' is False, any limit/offset information is not
included in the query.
"""
# The `do_offset` flag indicates whether we need to construct
# the SQL needed to use limit/offset with Oracle.
do_offset = with_limits and (self.query.high_mark is not None
or self.query.low_mark)
if not do_offset:
sql, params = super(SQLCompiler, self).as_sql(with_limits=False,
with_col_aliases=with_col_aliases)
else:
sql, params = super(SQLCompiler, self).as_sql(with_limits=False,
with_col_aliases=True)
# Wrap the base query in an outer SELECT * with boundaries on
# the "_RN" column. This is the canonical way to emulate LIMIT
# and OFFSET on Oracle.
high_where = ''
if self.query.high_mark is not None:
high_where = 'WHERE ROWNUM <= %d' % (self.query.high_mark,)
sql = 'SELECT * FROM (SELECT ROWNUM AS "_RN", "_SUB".* FROM (%s) "_SUB" %s) WHERE "_RN" > %d' % (sql, high_where, self.query.low_mark)
return sql, params
class SQLInsertCompiler(compiler.SQLInsertCompiler, SQLCompiler):
pass
class SQLDeleteCompiler(compiler.SQLDeleteCompiler, SQLCompiler):
pass
class SQLUpdateCompiler(compiler.SQLUpdateCompiler, SQLCompiler):
pass
class SQLAggregateCompiler(compiler.SQLAggregateCompiler, SQLCompiler):
pass
class SQLDateCompiler(compiler.SQLDateCompiler, SQLCompiler):
pass
|