psycopg2: Update multiple rows in a table with values from a tuple of tuples

问题

I'm attempting to update several rows at once using a tuple of tuples. I figured out how to construct the sql statement from this post, but implementing it in psycopg2 has proven to be more challenging. Here's what I have:

c = db.cursor()

new_values = (("Richard",29),("Ronald",30))

sql = """UPDATE my_table AS t 
         SET name = e.name 
         FROM (VALUES %s) AS e(name, id) 
         WHERE e.id = t.id;"""

c.execute(sql, (new_values,))

The result is an error: ProgrammingError: table "e" has 1 columns available but 2 columns specified This is because the FROM clause is being interpreted as:

FROM (VALUES (("Richard",29),("Ronald",30)))

instead of:

FROM (VALUES ("Richard",29),("Ronald",30))

I can work around this by doing the following but it seems unsafe:

import re
c = db.cursor()

sql = """UPDATE my_table AS t 
         SET name = e.name 
         FROM (VALUES %s) AS e(name, id) 
         WHERE e.id = t.id;"""
sql = c.mogrify(sql, (new_values,))

# Replace the first occurance of '((' with '('.
sql = sql.replace('((', '(',1)

# Replace the last occurance of '))' with ')'.
sql = re.sub(r'(.*)\)\)', r'\1)', sql)

sql = c.execute(sql)

Is there a better way to do this?

回答1:

This post pointed me in the right direction. The documentation for extras.execute_values also contains a great example using the UPDATE clause.

c = db.cursor()
update_query = """UPDATE my_table AS t 
                  SET name = e.name 
                  FROM (VALUES %s) AS e(name, id) 
                  WHERE e.id = t.id;"""

psycopg2.extras.execute_values (
    c, update_query, new_values, template=None, page_size=100
)

来源：https://stackoverflow.com/questions/47192163/psycopg2-update-multiple-rows-in-a-table-with-values-from-a-tuple-of-tuples

标签

python

postgresql

psycopg2