SQLAlchemy: print the actual query
In the vast majority of cases, the "stringification" of a SQLAlchemy statement or query is as simple as:
print(str(statement))
This applies both to an ORM Query
as well as any select()
or other statement.
Note: the following detailed answer is being maintained on the sqlalchemy documentation.
To get the statement as compiled to a specific dialect or engine, if the statement itself is not already bound to one you can pass this in to compile():
print(statement.compile(someengine))
or without an engine:
from sqlalchemy.dialects import postgresql
print(statement.compile(dialect=postgresql.dialect()))
When given an ORM Query
object, in order to get at the compile()
method we only need access the .statement accessor first:
statement = query.statement
print(statement.compile(someengine))
with regards to the original stipulation that bound parameters are to be "inlined" into the final string, the challenge here is that SQLAlchemy normally is not tasked with this, as this is handled appropriately by the Python DBAPI, not to mention bypassing bound parameters is probably the most widely exploited security holes in modern web applications. SQLAlchemy has limited ability to do this stringification in certain circumstances such as that of emitting DDL. In order to access this functionality one can use the 'literal_binds' flag, passed to compile_kwargs
:
from sqlalchemy.sql import table, column, select
t = table('t', column('x'))
s = select([t]).where(t.c.x == 5)
print(s.compile(compile_kwargs={"literal_binds": True}))
the above approach has the caveats that it is only supported for basic
types, such as ints and strings, and furthermore if a bindparam
without a pre-set value is used directly, it won't be able to
stringify that either.
To support inline literal rendering for types not supported, implement
a TypeDecorator
for the target type which includes a
TypeDecorator.process_literal_param
method:
from sqlalchemy import TypeDecorator, Integer
class MyFancyType(TypeDecorator):
impl = Integer
def process_literal_param(self, value, dialect):
return "my_fancy_formatting(%s)" % value
from sqlalchemy import Table, Column, MetaData
tab = Table('mytable', MetaData(), Column('x', MyFancyType()))
print(
tab.select().where(tab.c.x > 5).compile(
compile_kwargs={"literal_binds": True})
)
producing output like:
SELECT mytable.x
FROM mytable
WHERE mytable.x > my_fancy_formatting(5)
Given that what you want makes sense only when debugging, you could start SQLAlchemy with echo=True
, to log all SQL queries. For example:
engine = create_engine(
"mysql://scott:tiger@hostname/dbname",
encoding="latin1",
echo=True,
)
This can also be modified for just a single request:
echo=False
– ifTrue
, the Engine will log all statements as well as arepr()
of their parameter lists to the engines logger, which defaults tosys.stdout
. Theecho
attribute ofEngine
can be modified at any time to turn logging on and off. If set to the string"debug"
, result rows will be printed to the standard output as well. This flag ultimately controls a Python logger; see Configuring Logging for information on how to configure logging directly.Source: SQLAlchemy Engine Configuration
If used with Flask, you can simply set
app.config["SQLALCHEMY_ECHO"] = True
to get the same behaviour.