for_update=whatever always creates a "FOR UPDATE" query

[Fayaz Yusuf Khan]

When using

table.select(for_update='read')

The query string representation is still

SELECT "user".id 
FROM "user" FOR UPDATE

[Fayaz Yusuf Khan]

Test file

[Mike Bayer]

the docs state here that these behaviors are dialect specific:

http://docs.sqlalchemy.org/en/rel_0_8/core/expression_api.html?highlight=for_update#sqlalchemy.sql.expression.select

for_update=False –

when True, applies FOR UPDATE to the end of the resulting statement.

Certain database dialects also support alternate values for this parameter:

    With the MySQL dialect, the value "read" translates to LOCK IN SHARE MODE.
    With the Oracle and Postgresql dialects, the value "nowait" translates to FOR UPDATE NOWAIT.
    With the Postgresql dialect, the values “read” and "read_nowait" translate to FOR SHARE and FOR SHARE NOWAIT, respectively.

so here the behavior requires a mysql dialect:

from sqlalchemy import *
from sqlalchemy.dialects import mysql

def test():
    table = Table('user', MetaData(), Column('id', Integer, primary_key=True))
    query = table.select(for_update='read')
    assert "LOCK IN SHARE MODE" in str(query.compile(dialect=mysql.dialect()))


if __name__ == '__main__':
    test()