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from sqlalchemy.ext.compiler import compiles
from sqlalchemy.sql.functions import FunctionElement
from .sqltypes import UtcDateTime
class utcnow(FunctionElement):
"""UTCNOW() expression for multiple dialects."""
type = UtcDateTime()
@compiles(utcnow)
def default_sql_utcnow(element, compiler, **kw):
"""Assume, by default, time zones work correctly.
Note:
This is a valid assumption for PostgreSQL and Oracle.
"""
return 'CURRENT_TIMESTAMP'
@compiles(utcnow, 'mysql')
def mysql_sql_utcnow(element, compiler, **kw):
"""MySQL returns now as localtime, so we convert to UTC.
Warning:
MySQL does not support the use of functions for sqlalchemy
`server_default=` values. The utcnow function must be used as
`default=` when interacting with a MySQL server.
"""
return "CONVERT_TZ(CURRENT_TIMESTAMP, @@session.time_zone, '+00:00')"
@compiles(utcnow, 'sqlite')
def sqlite_sql_utcnow(element, compiler, **kw):
"""SQLite DATETIME('NOW') returns a correct `datetime.datetime` but does not
add milliseconds to it.
Directly call STRFTIME with the final %f modifier in order to get those.
"""
return r"(STRFTIME('%Y-%m-%d %H:%M:%f', 'NOW'))"
@compiles(utcnow, 'mssql')
def mssql_sql_utcnow(element, compiler, **kw):
"""MS SQL provides a function for the UTC datetime."""
return 'GETUTCDATE()'
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