How to make psycopg2 emit nested quotes?

问题

As per "relation does not exist" in pg_table_size, I need to emit nested single and double quotes:

import psycopg2  as pg
from psycopg2 import sql

conn = pg.connect("dbname=test user=test")
table_name = "testDB"
cu = conn.cursor()
cu.execute(sql.SQL("SELECT pg_table_size(%s)"), (table_name,))

emits SELECT pg_table_size('testDB') which raises

psycopg2.ProgrammingError: relation "testdb" does not exist

while

cu.execute(sql.SQL("SELECT pg_table_size({t})").format(t=sql.Identifier(table_name)))

emits SELECT pg_table_size("testDB") which raises

psycopg2.ProgrammingError: column "testDB" does not exist

Obviously,

cu.execute(sql.SQL("SELECT pg_table_size(%s)"),('"testDB"',))

works fine, but I want to find the "official" way to emit SELECT pg_table_size('"testDB"').

Experimentally, the following works:

cu.execute(sql.SQL("SELECT pg_table_size(%s)"),
           (sql.Identifier(table_name).as_string(conn), ))

is this TRT?

回答1:

You can use the Postgres function quote_ident(string text):

cu.execute("SELECT pg_table_size(quote_ident(%s))", (table_name, ))

I think your last example is a good alternative for the above solution.

来源：https://stackoverflow.com/questions/52670840/how-to-make-psycopg2-emit-nested-quotes