Adrian: On Thu, Oct 6, 2016 at 4:31 PM, Adrian Klaver <adrian.klaver@xxxxxxxxxxx> wrote: > This is how I can trigger the ERROR: This is how you can trigger the ISSUE, IMO it is a correct behaviour. Anyway, your example lacks some important details: 1.- SHOW your isolation level. 2.- SHOW your command interleaving. Here is an example session where IT WORKS like you pretend, and the table exists before starting showing those details: \set PROMPT1 'session1-%`date +%H:%M:%S` [%x]' session1-17:27:26 []start transaction isolation level serializable; START TRANSACTION session1-17:27:35 [*]drop table if exists ddl_test; DROP TABLE session1-17:27:44 [*]create table ddl_test(id int); CREATE TABLE session1-17:28:03 [*]commit; COMMIT session1-17:28:10 ----- \set PROMPT1 'session2-%`date +%H:%M:%S` [%x]' session2-17:27:29 []start transaction isolation level serializable; START TRANSACTION session2-17:27:39 [*]drop table if exists ddl_test; ****GAP**** DROP TABLE session2-17:28:10 [*]create table ddl_test(id int); CREATE TABLE session2-17:28:23 [*]commit; COMMIT session2-17:28:28 in the ***GAP*** mark session 2 was blocked, and it unblocked when I issued commit in session 1. ( note the timestamps of command end are the ones starting the next line, and except the one I marked they were nearly instant ) Note how you can follow the command interleaving and the isolation level. OTOH, as you point, not having the table shows the issue again: session1-17:33:56 []start transaction isolation level serializable; START TRANSACTION session1-17:33:59 [*]drop table if exists ddl_test; NOTICE: table "ddl_test" does not exist, skipping DROP TABLE session1-17:34:08 [*]create table ddl_test(id int); CREATE TABLE session1-17:34:19 [*]commit; COMMIT session2-17:28:28 []start transaction isolation level serializable; START TRANSACTION session2-17:34:04 [*]drop table if exists ddl_test; NOTICE: table "ddl_test" does not exist, skipping DROP TABLE session2-17:34:13 [*]create table ddl_test(id int); ERROR: duplicate key value violates unique constraint "pg_type_typname_nsp_index" DETAIL: Key (typname, typnamespace)=(ddl_test, 2200) already exists. session2-17:34:30 [!] This time session 2 stopped at the create table and direcly aborted when session1 commited. Correct, IMO, although antiestetic behaviour. I think it is due to drop being a no-op if table did not exist, as commands are not postponed ( it must show you the notice or not before completing ), so you are just issuing to create commands for the same table. Your serial postponed execution is a nice desire, but I doubt it is necessary . Francisco Olarte. -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
