Passing table name as a parameter in psycopg2, relation does not exist for a public table

Question

It seems like passing table name as a parameter in psycopg2 doesn't work for an outside public table. The code and result as below.Appreciate any helps.

This code works well. cursor.execute('select * from public.wc_test limit 1')

However, this code returns an error cursor.execute(sql.SQL('select * from {} limit 1').format(sql.Identifier('public.wc_test')))

ProgrammingError Traceback (most recent call last) in () ----> 1 cursor.execute(sql.SQL('select * from {} limit 1').format(sql.Identifier('public.wc_test'))) ProgrammingError: relation "public.wc_test" does not exist LINE 1: select * from "public.wc_test" limit 1

Here is the screenshot of the code and output

New Issue:

It seems I got the same issue again with another table, even I separated the schema and the table name. Do you have any ideas what results in this error? Thanks!

Here is the screenshot of the code and the output

Answer 1

The schema and table name must be passed separately otherwise they will finish being quoted together like in "public.wc_text" where it should be "public"."wc_test" . So either

cursor.execute(
    sql.SQL('select * from public.{} limit 1').format(
        sql.Identifier('wc_test')
    )
)

or

cursor.execute(
    sql.SQL('select * from {}.{} limit 1').format(
        sql.Identifier('public'),
        sql.Identifier('wc_test')
    )
)

Answer 2

You can use AsIs postrgresql extension method for this:

Adapter conform to the ISQLQuote protocol useful for objects whose string representation is already valid as SQL representation.

import psycopg2
from psycopg2.extensions import AsIs

QUERY = 'SELECT * from %(table)s limit 1'

data = {'table': AsIs('public.wc_test')}

with conn.cursor() as cursor:
    cursor.execute(QUERY, data)
    rows = cursor.fetchall()        
return rows