Eugene,
indeed, for now, MonetDB does not provide any vacuum functionality to physically remove deleted records. Basically, the physical representation of BATs as dense consecutive arrays that are one reason for MonetDB's efficient query processing, prohibit a "trivial" and efficient vacuum. In general, any vacuum would require an efford linear in the table size, basically copying all non-deleted record into a new location.
Thus, the two approaches you suggest are the most reasonable for now. An other alternative is to dump the table contents into a CSV file, clear the table contents, and bulkload it from CSV file, again, e.g., COPY SELECT * FROM <table> INTO <file>; DELETE FROM <table>; COPY INTO <table> FROM <file>; (obviously at the expense of serializing and parsing the whole data).
Stefan
On Wed, Jul 20, 2011 at 09:52:43AM +0400, Eugene Prokopiev wrote:
2011/7/14 Eugene Prokopiev enp@itx.ru:
I can't find VACUUM command in http://www.monetdb.org/Documentation, I see only vacuum cleaning algorithm mention in http://www.monetdb.org/Documentation/Manuals/SQLreference/Transactions. So, how can phisicaly delete rows after marking them as deleted?
I see it's impossible now - http://bugs.monetdb.org/show_bug.cgi?id=2541 :(
So I have only 2 options:
- copy all table contents to another table, drop old table, copy again
- emulate partitions with VIEW AS SELECT * FROM T1 UNION SELECT *
FROM T2 UNION ... and drop old partition
-- Thanks, Eugene Prokopiev
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