Postgresql updating millions of rows billy j miller dating
How can I make a Update of a column in a very large table for all rows without using the double amount of disc space and without any need for atomic operation?I have a very large table with about 60 million rows.Reads will be reasonably fast, but writes make RAID 5 look fast.Running a DB on a True Crypt volume will be torture for writes, especially random writes.The laptop's power setting were on High performance (Windows 7 x64). There are no triggers anywhere in this table or anywhere else in the database.
This probably won't help you at this point but it may someone else looking for answers.In Oracle, you would be writing a before image of each block being updated so that other session still have a consistent read without reading your modified blocks and you have the ability to rollback. You are usually better off to do the transactions in small chunks. If you have indexes on the table, and the table is going to be considered out of operation during maintenance, you are often better off to remove the indexes before a big operation and then recreating it again afterward.Cheaper then constantly trying to maintain the indexes with each updated record.A separate flag in the file system can well save the fact that that bulk update was in progress) for this, I don't care or want a abort or "all or nothing" like SQL mandates. If the update is halfway finished, that's okay.
The idea is basically that either this update succeeds or it succeeds or - there is no "not". If I just do an UPDATE table SET flag=0;then Pg will make a copy of every row which must be cleaned up by vaccuum.
INTO TEMPORARY TABLE master_tmp ; TRUNCATE TABLE consistent.master; -- Now DROP all constraints on consistent.master, then: INSERT INTO consistent.master SELECT * FROM master_tmp; -- ... These unlogged tables get truncated if the DB shuts down uncleanly while they're dirty.