vacuum

sqlite incremental vacuum removing only one free page

由 这一生的挚爱 提交于 2021-01-28 01:58:56
问题 I have changed value of auto_vacuum PRAGMA of my sqlite database to INCREMENTAL. When I run PRAGMA incremental_vacuum; through 'DB Browser for SQlite' application it frees all the pages in the free_list . But when I am running same statement using any SQLite library in C# (e.g. Microsoft.Data.SQLite ), it frees only one page from the free_list I verified this by getting the number in current free_list by running PRAGMA freelist_count before and after running PRAGMA incremental_vacuum

best disk saving strategy for “replacement inserts”

由 柔情痞子 提交于 2020-01-04 05:37:16
问题 Every day I delete hundreds of thousands of records from a large table, then I do some calculations (with new data) and replace every one of the records that I previously deleted. I thought doing regular vacuum tbl would do the trick. I know it doesn't return disk space to the server, but (because of the pg docs) I thought because I was inserting about as many records as I was deleting, I wouldn't loose any/much disk space. However, after moving the table to a different namespace (for an

How to reclaim space occupied by unused LOBs in PostgreSQL

由 為{幸葍}努か 提交于 2019-12-10 18:53:07
问题 I have a medium sized database cluster running on PostgreSQL 8.3. The database stores digital files (images) as LOBs. There is a fair bit of activity in the database cluster, a lot of content is created and deleted in an ongoing manner. Even though the application table which hosts the OIDs, gets maintained properly by the application (when an image file is deleted), the size of the database cluster grows continuously. Auto-vacuuming is active so this shouldn't happen. 回答1: LOBs are NOT

Postgres 8.4.4 (x32 on Win7 x64) very slow UPDATE on small table

由 谁都会走 提交于 2019-12-10 14:27:21
问题 I have a very simple update statement: UPDATE W SET state='thing' WHERE state NOT IN ('this','that') AND losttime < CURRENT_TIMESTAMP; The table W only has 90 rows, though the losttime and state columns for each row are updated each about every ~10s seconds. There are indexes on state and losttime (as well as the primary index). I'm noticing with large databases (i.e. the other tables have a lot of entries, not table W) over a period of time, the query gets slower and slower and slower. After

Amazon Redshift at 100% disk usage due to VACUUM query

由 狂风中的少年 提交于 2019-12-09 09:42:26
问题 Reading the Amazon Redshift documentatoin I ran a VACUUM on a certain 400GB table which has never been vacuumed before, in attempt to improve query performance. Unfortunately, the VACUUM has caused the table to grow to 1.7TB (!!) and has brought the Redshift's disk usage to 100%. I then tried to stop the VACUUM by running a CANCEL query in the super user queue (you enter it by running "set query_group='superuser';") but although the query didn't raise an error, this had no effect on the

why writes in a table prevent vacuums in another?

由 瘦欲@ 提交于 2019-12-08 03:31:02
问题 Having READ COMMITTED isolation level, idle transactions that have performed a write operation will prevent vacuum to cleanup dead rows for the tables that transaction wrote in. That is clear for tables that were written by transactions that are still in progress. Here you can find a good explanation. But it is not clear to me why this limitation affects also to any other tables. For example: transaction T is started and it updates table B, vacuum is executed for table A while T is in "idle

Perform VACUUM FULL with JPA

由 北慕城南 提交于 2019-12-08 00:03:37
问题 I'm using a PostgreSQL DB and I would like to start VACUUM FULL using JPA EntityManager. Version 1 public void doVacuum(){ entityManager.createNativeQuery("VACUUM FULL").executeUpdate() } throws TransactionRequiredException Version 2 @Transactional public void doVacuum(){ entityManager.createNativeQuery("VACUUM FULL").executeUpdate() } throws PersistenceException "VACUUM cannot run inside a transaction block" Version 3 public void doVacuum(){ entityManager.createNativeQuery("VACUUM FULL")

why writes in a table prevent vacuums in another?

由 百般思念 提交于 2019-12-07 03:52:28
Having READ COMMITTED isolation level, idle transactions that have performed a write operation will prevent vacuum to cleanup dead rows for the tables that transaction wrote in. That is clear for tables that were written by transactions that are still in progress. Here you can find a good explanation. But it is not clear to me why this limitation affects also to any other tables. For example: transaction T is started and it updates table B, vacuum is executed for table A while T is in "idle in transaction" state. In this scenario, why dead rows in A cannot be removed? Here what I did: # show

Is it possible to issue a “VACUUM ANALYZE <tablename>” from psycopg2 or sqlalchemy for PostgreSQL?

由 ⅰ亾dé卋堺 提交于 2019-12-07 00:53:55
问题 Well, the question pretty much summarises it. My db activity is very update intensive, and I want to programmatically issue a Vacuum Analyze. However I get an error that says that the query cannot be executed within a transaction. Is there some other way to do it? 回答1: This is a flaw in the Python DB-API: it starts a transaction for you. It shouldn't do that; whether and when to start a transaction should be up to the programmer. Low-level, core APIs like this shouldn't babysit the developer

Database table size did not decrease proportionately

由 穿精又带淫゛_ 提交于 2019-12-06 20:22:34
问题 I am working with a PostgreSQL 8.4.13 database. Recently I had around around 86.5 million records in a table. I deleted almost all of them - only 5000 records are left. I ran reindex and vacuum analyze after deleting the rows. But I still see that the table is occupying a large disk space: jbossql=> SELECT pg_size_pretty(pg_total_relation_size('my_table')); pg_size_pretty ---------------- 7673 MB Also, the index value of the remaining rows are pretty high still - like in the million range. I
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