El 25/11/20 a las 15:45, Daniele Varrazzo escribió:
On Wed, 25 Nov 2020 at 12:29, listas <lis...@soft-com.es> wrote:
After reading the docs i have a question about the parameters in the
'in' clause.
In psycopg2 i do:
params = (1,2,3,4)
cursor.execute("select * from mytable where field1 in %s", (params,))
or
params = ('black','red','green')
cursor.execute("select * from mytable where field2 in %s", (params,))
What will it be like in psycopg3, will it be the same?, will I have to
create a special adapter?
Hollo Oswaldo,
"IN" cannot be used, because it's a SQL construct, so "(1, 2, 3)" is
not something that postgres will understand as a parameter.
You can use "= any (%s)" and pass a list. This is something you can do
in psycopg2 too, and it's actually a better choice, because it works
with empty lists too, unless `IN ()`, which is a syntax error for
Postgres.
What you can do is:
params = ['black','red','green']
cursor.execute("select * from mytable where field2 = any(%s)", (params,))
interesting fact: "= any" is what postgres really uses internally,
even if you use the "IN ()" syntax:
piro=# explain select * from mytable where myint in (1,2,3);
QUERY PLAN
---------------------------------------------------------
Seq Scan on mytable (cost=0.00..45.06 rows=38 width=4)
Filter: (myint = ANY ('{1,2,3}'::integer[]))
(2 rows)
-- Daniele
Thank for your replies, I will use "=any(params list)" in psycopg3
The second question is: if psycopg3 is going to do the automatic cast of
the types, will it be able to distinguish between a json and a list of
values?.
Example:
data = ["a", "b", "c"]
idList = [4,7,2]
cursor.execute("update mytable set jsfield=%s where id = any(%s)",
(data, idList))
What will be the correct syntax in this case?
Thanks,
--
Oswaldo Hernández
