Paweł Domański
35 lines
1.0 KiB
SQL
35 lines
1.0 KiB
SQL
VACUUM FULL - > JUST LIKE MOVE COMMAND IN ORACLE . IT TAKES MORE TIME, BUT IT RETURNS THE SPACE TO OS BECAUSE OF ITS COMPLEX ALGORITHM. IT also requires additional disk space , which can store the new copy of the table., until the activity is completed. Also it locks the table exclusively, which block all operations on the table .
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-- Command to run vacuum full command for table:
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dbaclass=# VACUUM FULL dbatest.emptab;
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VACUUM
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DEMO TO CHECK HOW IT RECLAIMS SPACE:
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-- Check existing space and delete some data:
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dbaclass=# select pg_size_pretty(pg_relation_size('dbatest.emptab'));
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pg_size_pretty
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----------------
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114 MB
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(1 row)
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dbaclass=# delete from dbatest.emptab where oid=13634;
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DELETE 131072
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-- We can observe size is still same:
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dbaclass=# select pg_size_pretty(pg_relation_size('dbatest.emptab'));
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pg_size_pretty
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----------------
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114 MB
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(1 row)
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-- Run vacuum full and observe the space usage:
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dbaclass=# VACUUM FULL dbatest.emptab;
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VACUUM
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dbaclass=# select pg_size_pretty(pg_relation_size('dbatest.emptab')); |