I have the hang issue in Postgres, When I am going to insert into record in a table. Table structure is enclosed in the discussion.
Also we found the issue with unique indexes. When I removed the unique index insert operation is working fine. I need help from this core group that weather this is the bug in the Postgres code or we are using unique index wrongly. Regards Tarkeshwar From: Niklas Andersson Sent: 09 July 2014 18:21 To: M Tarkeshwar Rao; Leo Zhou; postgres-disc...@mailman.lmera.ericsson.se Subject: RE: [postgres-discuss] Insert query hangs I wouldn't advice you to drop the indexes in a production environment, as they are usually very important to get fast queries. Your index doesn't seem to be of much use though, as it looks like you are only indexing one single column that is an integer. It seems as it is not needed. Usually you use indexes with two or more columns to speed up queries, or you join on those columns. If you want to make sure that that column is unique, I would advice you to define it as a primary key. You could also use the keyword unique, but in this case I would prefer to define it as a primary key. Then in order to always get a new, unique integer as a primary key, I would suggest you have a look at CREATE SEQUENCE. The syntax comes from how Oracle does it and it works very nice [1] But, this doesn't explain why your current index is causing problems, becuase it _shouldnt_ ;-/ I think you would need some tools to have a check on the server load. Or have a look at how EXPLAIN works, Unfortunately I don't have that deep competence :-( [1] http://www.postgresql.org/docs/8.1/static/sql-createsequence.html Regards, Niklas ________________________________ From: M Tarkeshwar Rao Sent: Wednesday, 09 July 2014 2:29 PM To: Niklas Andersson; Leo Zhou; postgres-disc...@mailman.lmera.ericsson.se<mailto:postgres-disc...@mailman.lmera.ericsson.se> Subject: RE: [postgres-discuss] Insert query hangs What should I do resolve this issue? Change the structure of Table or I should not create the index. From: Niklas Andersson Sent: 09 July 2014 17:58 To: M Tarkeshwar Rao; Leo Zhou; postgres-disc...@mailman.lmera.ericsson.se<mailto:postgres-disc...@mailman.lmera.ericsson.se> Subject: RE: [postgres-discuss] Insert query hangs Yes, and the more data, the longer it takes to rebuild the index. This is why you drop the indexes during certain copy operations, if you have indexes enabled the copy would take forever. Regards, Niklas ________________________________ From: M Tarkeshwar Rao Sent: Wednesday, 09 July 2014 2:22 PM To: Niklas Andersson; Leo Zhou; postgres-disc...@mailman.lmera.ericsson.se<mailto:postgres-disc...@mailman.lmera.ericsson.se> Subject: RE: [postgres-discuss] Insert query hangs Fine now I understand why it is taking time. Is it possible that insert operation will take time when unique index is already created on the table and table has some data within it? From: Niklas Andersson Sent: 09 July 2014 17:20 To: M Tarkeshwar Rao; Leo Zhou; postgres-disc...@mailman.lmera.ericsson.se<mailto:postgres-disc...@mailman.lmera.ericsson.se> Subject: RE: [postgres-discuss] Insert query hangs Can this be of help [1]? [1] http://www.postgresql.org/docs/9.2/static/sql-createindex.html#SQL-CREATEINDEX-CONCURRENTLY Regards, Niklas ________________________________ From: M Tarkeshwar Rao Sent: Wednesday, 09 July 2014 1:41 PM To: Niklas Andersson; Leo Zhou; postgres-disc...@mailman.lmera.ericsson.se<mailto:postgres-disc...@mailman.lmera.ericsson.se> Subject: RE: [postgres-discuss] Insert query hangs CREATE TABLE eventlogentry ( tableindex integer, object character varying(80), method character varying(80), bgwuser character varying(80), "time" character(23), realuser character varying(80), host character varying(80), application character varying(80) ) WITH ( OIDS=FALSE ) TABLESPACE mmdata; ALTER TABLE eventlogentry OWNER TO mmsuper; GRANT ALL ON TABLE eventlogentry TO mmsuper; GRANT SELECT ON TABLE eventlogentry TO report; CREATE UNIQUE INDEX ind1_eventlogentry ON eventlogentry USING btree (tableindex ) TABLESPACE mmindex; I am sharing the table structure. When we removed the unique index it is working fine. And when created normal index(not unique) it is working fine. After removing unique index we tried to recreate it but it is giving following infinite logs : concurrent insert in progress within table "eventlogentry" caveat when building a unique index concurrently is that the uniqueness constraint is already being enforced against other transactions when the second table scan begins Regards Tarkeshwar From: Niklas Andersson Sent: 09 July 2014 16:10 To: M Tarkeshwar Rao; Leo Zhou; postgres-disc...@mailman.lmera.ericsson.se<mailto:postgres-disc...@mailman.lmera.ericsson.se> Subject: RE: [postgres-discuss] Insert query hangs Hi, You have some info on checking on corrupt tables here [1], but I am pretty sure you'll be helped by using the REINDEX option [2]. If you have lots of data, and lots of inserts sometimes you can run into performance issues. I.e the server doesn't have the time to rebuild the index at the speed you're sending inserts. But then the app still wouldn't hang, but almost grind to a halt and give you sluggish performance. Now, I don't know if this database has lots of deletes, but sometimes it makes sense to clean it up a bit. (Think: defrag), then VACUUM is helpful [3] [1] http://blog.apptamers.com/post/32050443731/corrupted-postgres-table [2] http://www.postgresql.org/docs/8.1/static/sql-reindex.html [3] http://www.postgresql.org/docs/9.1/static/sql-vacuum.html Regards, Niklas ________________________________ From: M Tarkeshwar Rao Sent: Wednesday, 09 July 2014 12:32 PM To: Niklas Andersson; Leo Zhou; postgres-disc...@mailman.lmera.ericsson.se<mailto:postgres-disc...@mailman.lmera.ericsson.se> Subject: RE: [postgres-discuss] Insert query hangs Actually problem is in customer site in their production environment. They have their database MDB. In that db they have insert issue with one table. They shared the data folder with us. We past the same data folder in our local DB which has the same name MDB and reproduced the issue. After reproducing the issue we run pg_dump(with data) on corrupted table and restore it on another local db. After restoring in another db we tested the insert operation and found it is working fine. We analysed one more thing when we removed the unique index from the table it is working fine. Is there any issue in indexing? Is there any option to repair the table or its indexing? Regards Tarkeshwar From: Niklas Andersson Sent: 09 July 2014 15:44 To: M Tarkeshwar Rao; Leo Zhou; postgres-disc...@mailman.lmera.ericsson.se<mailto:postgres-disc...@mailman.lmera.ericsson.se> Subject: RE: [postgres-discuss] Insert query hangs Ah, then it sounds like you had corrupt data in that first table. When you did the pgdump, did you also export and import the data and not only the structure? Regards, Niklas ________________________________ From: M Tarkeshwar Rao Sent: Wednesday, 09 July 2014 12:05 PM To: Niklas Andersson; Leo Zhou; postgres-disc...@mailman.lmera.ericsson.se<mailto:postgres-disc...@mailman.lmera.ericsson.se> Subject: RE: [postgres-discuss] Insert query hangs You mean to say diff in the name of the table? I have done one more thing I imported(using pgdump) the 2nd table(which have the hang issue) in another DB. In the 2nd DB it is working fine. Regards Tarkeshwar From: Niklas Andersson Sent: 09 July 2014 15:21 To: M Tarkeshwar Rao; Leo Zhou; postgres-disc...@mailman.lmera.ericsson.se<mailto:postgres-disc...@mailman.lmera.ericsson.se> Subject: RE: [postgres-discuss] Insert query hangs Well...in that case I would export the database schema and run a diff on the tables. If the structure is identical, the only thing left is the actual naming. If you have non-ascii characters or some unicode-stuff, doing a diff would tell you that. Sometimes it is hard to see issues like that with the eye. Regards, Niklas ________________________________ From: M Tarkeshwar Rao Sent: Wednesday, 09 July 2014 11:46 AM To: Niklas Andersson; Leo Zhou; postgres-disc...@mailman.lmera.ericsson.se<mailto:postgres-disc...@mailman.lmera.ericsson.se> Subject: RE: [postgres-discuss] Insert query hangs It just a plain insert statement. We are not using triggers in it. Just a simple table with 6 columns one integer and rest are varchar(80) fields. We are firing insert from command prompt. Two tables with same structure and same data. Insert on one table working fine but for 2nd table it is going in hanging state. Regards Tarkeshwar From: Niklas Andersson Sent: 09 July 2014 15:03 To: M Tarkeshwar Rao; Leo Zhou; postgres-disc...@mailman.lmera.ericsson.se<mailto:postgres-disc...@mailman.lmera.ericsson.se> Subject: RE: [postgres-discuss] Insert query hangs Can it be a trigger [1] or some PL/SQL statement that hangs? If the table structure is identical that is? [1] http://www.postgresql.org/docs/9.0/static/trigger-definition.html Regards, Niklas ________________________________ From: postgres-discuss-boun...@mailman.lmera.ericsson.se<mailto:postgres-discuss-boun...@mailman.lmera.ericsson.se> [postgres-discuss-boun...@mailman.lmera.ericsson.se] on behalf of M Tarkeshwar Rao Sent: Wednesday, 09 July 2014 11:13 AM To: Leo Zhou; postgres-disc...@mailman.lmera.ericsson.se<mailto:postgres-disc...@mailman.lmera.ericsson.se> Subject: Re: [postgres-discuss] Insert query hangs Hi Leo, We have a table in a database DB1 with name Test. We imported this database from another machine. When I fire insert statement it is going in the hang state. Then I created another table with same structure and with same data within it as in table Test. Then I fired the insert statement. It is working fine. I am not able find the reason for this. Can you please help me out on this. This scenario easily reproducible. I have a standalone system and postgresql 9.1 installed on it. Regards Tarkeshwar From: Leo Zhou Sent: 19 June 2014 15:40 To: M Tarkeshwar Rao; postgres-disc...@mailman.lmera.ericsson.se<mailto:postgres-disc...@mailman.lmera.ericsson.se> Subject: RE: [postgres-discuss] Insert query hangs Hi Tarkeshwar, According to my experience, if you are using standalone PG server, it could be transaction confliction. For example one session insert data into table, but other session lock table or change table. You can check the pg_lock system view. Refer to : https://wiki.postgresql.org/wiki/Lock_Monitoring. BRs, Leo From: postgres-discuss-boun...@mailman.lmera.ericsson.se<mailto:postgres-discuss-boun...@mailman.lmera.ericsson.se> [mailto:postgres-discuss-boun...@mailman.lmera.ericsson.se]<mailto:[mailto:postgres-discuss-boun...@mailman.lmera.ericsson.se]> On Behalf Of M Tarkeshwar Rao Sent: Thursday, June 19, 2014 5:13 PM To: postgres-disc...@mailman.lmera.ericsson.se<mailto:postgres-disc...@mailman.lmera.ericsson.se> Subject: [postgres-discuss] Insert query hangs Importance: High Hi, Insert query hangs, what could be the reason. Is there any way to find out? Any timeout feature is there with query which can be set at client or server end? We need Postgres debug steps. How can we set the debugging option? Regards Tarkeshwar
