My jabber server had the feature, that it logs all messages that got sent through it.
This is pretty cool, and useful. And now, i got asked to use it to create list of conversations.
What exactly is this? Whenever I send (or receive) something there is record in database with information about which local user, communication type (send/recv), correspondent, when it happened, and what is the body of message.
And based on this, we want to list messages into chats. How?
This question (and its variants) show quite often on #postgresql on IRC. People get sequential scans, and are worried that it's slow and bad.
So, I hope that this blogpost will shed some light on the subject why indexes are being chosen to be used, or not.
I'm quite often doing stuff on remote machines, and quite frequently I start some long-running job, when I remember that I didn't ran it via screen – so it will break, if my network connection will die.
Is there any sane way to start screen automatically? YES.
On 24th of August, Takahiro Itagaki committed patch:
Log Message: ----------- Add string functions: concat(), concat_ws(), left(), right(), and reverse(). Pavel Stehule, reviewed by me.
Continue reading Waiting for 9.1 – concat, concat_ws, right, left, reverse
Every now and then somebody asks how to make diff of database schemata.
Usual background is like: we have production database, and development database, and we want to see what is different on development to be able to change production in the same way.
Personally I think that such approach is inherently flawed. Why?
Well, the biggest information is that hot-backups on slave work. And they work fine. Really fine.
Some more information (with nice graph!):
“Zainspirowany" pismem o kuchni amerykańskiej, zrobiłem sobie słodko-ostry chłodnik arbuzowy. Wyszło nieźle, więc dla potomności:
Yesterday (August, 7th), Tom Lane committed:
Log Message: ----------- Recognize functional dependency on primary keys. This allows a table's other columns to be referenced without listing them in GROUP BY, so long as the primary key column(s) are listed in GROUP BY. Eventually we should also allow functional dependency on a UNIQUE constraint when the columns are marked NOT NULL, but that has to wait until NOT NULL constraints are represented in pg_constraint, because we need to have pg_constraint OIDs for all the conditions needed to ensure functional dependency. Peter Eisentraut, reviewed by Alex Hunsaker and Tom Lane
Continue reading Waiting for 9.1 – Recognize functional dependency on primary keys.
On 28th of July, Simon Riggs committed patch which:
Log Message: ----------- Reduce LOCK levels OF CREATE TRIGGER AND SOME ALTER TABLE, CREATE RULE actions. Avoid hard-coding lockmode used FOR many altering DDL commands, allowing easier future changes OF LOCK levels. Implementation OF initial analysis ON DDL sub-commands, so that many LOCK levels are now at ShareUpdateExclusiveLock OR ShareRowExclusiveLock, allowing certain DDL NOT TO block reads/writes. FIRST OF NUMBER OF planned changes IN this area; additional docs required WHEN FULL project complete.
Continue reading Waiting for 9.1 – Reduced lock levels for ALTER TABLE
Some guy came to #postgresql today. Described his problem, got additional question, and then … well .. I wouldn't believe if it didn't happen to me.
Continue reading How to make sure you will not get any help on IRC