We have table "table1" containing 100000 rows, which includes blob data. The total table size is 3.5 GB.
When tried to extract all records into CSV/.txt file by using copy or \o commands the generated output file is 100 GB in size.
ex:
select pg_size_pretty(pg_total_relation_size('table1));
3.5 GB
Please let us know how this actually generated this much huge size and how will get know the actual table size?
Related
I have a table that consist of 20k records. I want to export it to excel. Is it possible to split the total records equally to 5 different excel or sheet?
Let say 20k records to 5 different excel. So each excel will contain 4k unique records.
I am working on a use case where initial data load for name table in PostgreSQL DB will be around 650 million rows with average row size of 0.6 KB bringing table size up to 400 GB. After that there could be up to 20,000 inserts or updates on daily basis.
I am new to PostgreSQL, want to check if I should consider partitioning looking at the table size.
Updating some information from Comments section:
It is an OLTP application for Identity resolution for business names, this is one specific table where all the business names are stored along with the metadata such as Start Date, End Date and any incoming name is matched with existing names to identify if it is related to another business. This table is updated throughout the day using batch files from different data sources.
Also, we are not planning to expire or remove any data from this table.
I want to know the size of my Table (postgresql). I make this query:
select pg_size_pretty(pg_table_size('mytable'));
Result: 8192 bytes
Then, I add 4 rows and the result is the same (8192 bytes).
What am I doing wrong? What am I missing?
Thanks a lot...
Postgres puts records in fixed-size pages, which are 8kB each by default. Storage is allocated one page at a time. Once you add enough rows to reach your table's fillfactor, it will add a second block, and the size will jump to 16384 bytes.
In PostgreSQL, how can I tell whether a text column is stored inline or stored in a "background table"?
Documentation for text column types says that
Very long values are also stored in background tables so that they do not interfere with rapid access to shorter column values.
Is there a fixed length at which a value is determined to be "very long"? If not, are there other ways of telling how my columns are laid out on disk? I have a table with several columns that are text (or varchar(n)) and want to understand how they are stored under the hood. Is there more documentation on these "background tables" somewhere?
Any varlena data type (all types with variable length or types longer than 4 bytes (32 bits) or 8 bytes (64 bits)) can be TOASTed - TOAST is a process that tries to reduce long rows (records) to 8KB page size.
Row size is checked before physically storing to the relation. When the size exceeds 2KB, most larger fields are selected, compressed, sliced to 2KB chunks and moved to a secondary table file with the suffix _toast. A pointer to the toast file replaces the data in the main storage. This process is repeated while the row is bigger than 2KB.
Follow the links provided by a_horse_with_no_name and IMSoP for more detailed documentation.
If your table is called t1, then enter \d+ t1 at your psql prompt, it will show a column storage mode.
I have been asked to determine how much data our application uses and how fast it is growing. The problem is many applications share the same database and tables with a column being used to determine which application the data belongs to. It is a DB2 database.
Is there any way to find the size in bytes of all the columns a table uses for a given row? It is important that I select only those rows that belong to my application.
If a column is not nullable I do not include it in the SQL I just multiply its size by the row count. I am primarily trying to determine the average size of nullable and variable size columns (we use VARCHAR and BLOB).
At the moment what I am doing looks something like this:
SELECT VALUE(LENGTH(COLUMN_1), 0) AS LEN_COL_1, repeat for each variable size column
FROM TABLE T
WHERE T.APP_ID = my app
The most accurate way to determine size would be to look at the sizes of the files that make up the DB2 tables.
Divide the file sizes by the percentage of rows that belong to your application.
This way, you count most of DB2's overhead size, including indexes.