How to monitor allocation data in tablespaces with partitioned table?
I want to know when my tablespaces will fill up before creating new tablespaces with new partition.
When I perform command:
db2pd -db DBTEST -tablespace
I got information with tablespace Statistics: UsablePgs and FreePgs.
The values remain the same even when I perform runstat on my table.
I thought that after runstat this value will grow.
The information returned by this call doesn't depend on runstats.
Think about this allocation info as "always current".
Consider using MON_GET_TABLESPACE
https://www.ibm.com/support/knowledgecenter/en/SSEPGG_11.1.0/com.ibm.db2.luw.sql.rtn.doc/doc/r0053943.html
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I'm managing a PostgreSQL database server for some users who need to create temporary tables. One user accidentally sent a query with ridiculously many outer joins, and that completely filled the disk up.
PostgreSQL has a temp_file_limit parameter but it seems to me that it is not relevant:
It should be noted that disk space used for explicit temporary tables, as opposed to temporary files used behind-the-scenes in query execution, does not count against this limit.
Is there a way then to put a limit on the size on disk of "explicit" temporary tables? Or limit the row count? What's the best approach to prevent this?
The only way to limit a table's size in PostgreSQL is to put it in a tablespace on a file system of an appropriate size.
Since temporary tables are created in the default tablespace of the database you are connected to, you have to place your database in that size restricted tablespace. To keep your regular tables from being limited in the same way, you'd have to explicitly create them in a different, less limited tablespace. Make sure that your user has no permissions on that less limited tablespace.
This is a rather unappealing solution, so maybe you should rethink your requirement. After all, the user could just as well fill up the disk by inserting the data into a permanent table.
How to find dead tuples size in postgresql ?
I have created backup of database using pg_dump and restored it on other server. I see there is database size difference (5 GB)in both database. I have verified the table live tuples and dead tuples. There is numbers of row difference due to new data added in current database. However it is big difference in restored DB size. What is the cause of it ? I didn't do vacuum analyze on restored database yet.
I see there is no dead tuples on restored database this may be one reason. That's why I want to find deadtuples size.
This is the view that you need to check:
select n_live_tup, n_dead_tup, relname from pg_stat_all_tables;
You can use the extension pgstattuple. It will report dead_tuple_len.
I'm migrating from a proprietary dbms to PG. In the proprietary dbms, "offlining" and "onlining" data partitions is a very lightweight operation. I'm looking to implement similar functionality with PG by backup and restore of individual table (partitions). Obviously I need to avoid a performance regression. So my question is what the fastest way is of:
Backing up a table (partition), both data and indexes
Taking the table offline (meaning that the data is now gone from the database)
Restoring the table (partition), both data and indexes
Once I have some advice I can design more targeted performance comparisons. Thanks in advance for any pointers.
What is fast and needs to be fast is adding or removing a partition (ALTER TABLE ... ATTACH/DETACH PARTITION).
After you have detached the partition you are in no great hurry to backup/export the data. This can be done comfortably with pg_dump.
Similarly, importing the data for a table that is to become a new partition is normally not time critical.
If you need this to happen faster (for example, you want the old partition to be visible in another database as soon as it is detached in the old one), you could use logical replication to replicate the partition to another PostgreSQL database before you detach it. As soon as replication has caught up, you detach or drop the original partition and attach the copy in the other database.
I've been trying postgres with a program that fetches data and puts it into the DB.
Right now the tablespace has filled the available space.
How can I cleanup the db in order to reduce it.
If I delete records, will the disk space be released?
Since I'd want to keep this under control, how can I say to postgres tablespace not to autoextend but to have a specific maximum sze?
Thanks
What is the hierarchy of Database related objects in postgres SQL?
Should it be like, table space must be created at instance level unlike other RDBMS(where we have table space under database).
If so we create the table space at instance level, what is the purpose of database? and what is difference between table space and database on postgres server?
An instance (in PostgreSQL called cluster) is a data directory initialized with initdb with a PostgreSQL server process.
A tablespace is a directory outside the data directory where objects can also be stored. Tablespaces are useful for certain corner cases like distributing I/O or limiting space for a subset of the data.
A database is a container for objects with permissions, organized in schemas.
The difference is that tablespaces are a physical concept, it defines a space where the data are stored, while databases are a logical concept about how data are organized, what they mean, how they are related, who is allowed to access them and so on.
The two concepts are orthogonal.
A database can have tables in several tablespaces, and a tablespace can contain data from several databases.
Database is where you organize all your objects. Tablespace is just storage space for those object.
You can storage your db object in different Tablespace. For example one table is storage in a Tablespace in diskA but another Table use a Tablespace in diskB to improve the performance. Or maybe you need a tablespace for big tables and dont mind use a slow big HDD for those objects.