What can be done to prevent having to restart a PC after a program (C++Builder) terminated abnormaly without closing the database using firebird 2?
What I am looking for: I would like to be able to just restart the program without any other intervention. (I could have the user call a batch file executing some cleanup or add some lines of code to the program to disconnect everything.)
If your database is firebird 2.1+, there are monitoring tables that show the active connections, and the sysdba can manually delete any left-over connnections.
If you look in your release notes, the syntax details should be there.
Related
I'm wondering if it's possible to have psql start a transaction automatically when I open a psql session on the command line. I know I can start a transaction manually using 'BEGIN;' but I'm wondering if that can be done automatically without me typing in 'BEGIN;' manually on the command line.
Thanks!
I did a google search but that didn't come up with any good results.
You cannot have psql start a transaction when you login, but you can have it start a transaction with the first SQL statement you enter. For that, put a .psqlrc file into your home directory and give it the following content:
\set AUTOCOMMIT off
Note that that is a very bad idea (in my personal opinion). You are running the risk to inadvertently start a transaction that holds locks and blocks the progress of autovacuum. I have seen more than one PostgreSQL instance that suffered serious damage because of administrators who disabled autocommit in their interactive clients and kept transactions open. At the very least, add the following to your .psqlrc:
SET idle_in_transaction_session_timeout = '1min';
Is there a way to submit a command in datagrip to a database without keeping the connection open / asynchronously? I'm attempting to create indexes concurrently, but I'd also like to close my laptop.
My datagrip workflow:
Select column in a database, click 'modify column', and eventually run code such as:
create index concurrently batchdisbursements_updated_index
on de_testing.batchdisbursements (updated);
However, these run as background tasks and cancel if I exit datagrip.
However, these run as background tasks and cancel if I exit datagrip.
What if you close your laptop without exiting datagrip? Datagrip is probably actively sending a cancellation message to PostgreSQL when you exit it. If you just close the laptop, I doubt it will do that. In that case, PostgreSQL won't notice the client has gone away until it tries to send a message, at which point the index creation should already be done and committed.
But this is a fragile plan. I would ssh to the server, run screen (or one of the fancier variants), run psql in that, and create the indexes from there.
I'm having a remote machine that's using postgresql 9.2.1. Suddenly, i couldn't start my pgsql server(pg_isready command is rejecting connections). what my doubt is that, is there any possibility that i can start my database in Standalone back end mode, while it is not opening in Normal user mode?
And, what is the difference in starting the pgsql server in those two modes?
Thanks in advance.
Rather than using single user mode, look into the PostgreSQL server log file. That should tell you what the problem is.
In single-user mode, there will be just a single process accessing the database; none of the background processes are started. You'll be superuser, and the database process will last only for the duration of your session. This is something for emergency recovery, like when system tables are corrupted, you forgot your superuser password and so on.
In your case, single-user mode will probably only help if the database shut down because of an impending transaction ID wraparound. You can then issue the saving VACUUM (FREEZE) in single-user mode.
As soon as you have fixed your problem, upgrade to a supported release of PostgreSQL.
I know database indexes can become corrupted if the server crashes. If I do:
sudo service postgresql restart
can that cause the same kind of corruption as a server crash?
That depends on the system I belive. You should look into the script to check the actual command issued. Eg. here we see, that restart is equal to stop & start. then checking stop we see it does killproc postmaster and removes pid. From the man killproc sends SIGTERM if otherly not specified. By the documentation
SIGTERM
This is the Smart Shutdown mode. After receiving SIGTERM, the
server disallows new connections, but lets existing sessions end their
work normally. It shuts down only after all of the sessions terminate.
If the server is in online backup mode, it additionally waits until
online backup mode is no longer active. While backup mode is active,
new connections will still be allowed, but only to superusers (this
exception allows a superuser to connect to terminate online backup
mode). If the server is in recovery when a smart shutdown is
requested, recovery and streaming replication will be stopped only
after all regular sessions have terminated.
So in presented case, indexes should survive. But you definetely should watch your /etc/init.d/ script to be sure.
I have dozens of unlogged tables, and doc says that an unlogged table is automatically truncated after a crash or unclean shutdown.
Based on that, I need to check some tables after database starts to see if they are "empty" and do something about it.
So in short words, I need to execute a procedure, right after database is started.
How the best way to do it?
PS: I'm running Postgres 9.1 on Ubuntu 12.04 server.
There is no such feature available (at time of writing, latest version was PostgreSQL 9.2). Your only options are:
Start a script from the PostgreSQL init script that polls the database and when the DB is ready locks the tables and populates them;
Modify the startup script to use pg_ctl start -w and invoke your script as soon as pg_ctl returns; this has the same race condition but avoids the need to poll.
Teach your application to run a test whenever it opens a new pooled connection to detect this condition, lock the tables, and populate them; or
Don't use unlogged tables for this task if your application can't cope with them being empty when it opens a new connection
There's been discussion of connect-time hooks on pgsql-hackers but no viable implementation has been posted and merged.
It's possible you could do something like this with PostgreSQL bgworkers, but it'd be a LOT harder than simply polling the DB from a script.
Postgres now has pg_isready for determining if the database is ready.
https://www.postgresql.org/docs/11/app-pg-isready.html