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Questions tagged [wal]

WAL, or write-ahead log, is a form of journalling used as part of crash-safety and atomic commit support in databases like PostgreSQL and SQLite.

PostgreSQL's write-ahead log is a crucial feature that permits crash-safety and atomic commit to be implemented. It's also heavily used in PostgreSQL's point-in-time recovery, streaming replication, and archive based replication features, as well as hot physical backup.

In SQLite, the default method by which SQLite implements atomic commit and rollback is a rollback journal. Beginning with version 3.7.0, a new "Write-Ahead Log" option (hereafter referred to as "WAL") is available.

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Re-enabling table logging on PostgreSQL

We recently had a PostgreSQL database with some of the tables having WAL turned off. ALTER TABLE some_table SET UNLOGGED; If I was to enable the Logging again. ALTER TABLE some_table SET LOGGED; Does this make it as if logging was always turned…
Scott Francis
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Optimize JSON denormalization using JQ - "cartesian product" from 1:N

I have a JSON database change log, output of wal2json. It looks like this: {"xid":1190,"timestamp":"2018-07-19 17:18:02.905354+02","change":[ {"kind":"update","table":"mytable2","columnnames":["id","name","age"],"columnvalues":[401,"Update…
Ondra Žižka
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Sqlite WALmode do not support memory mode?

I create my sqlite DB connection by using memory mode: connection = DriverManager.getConnection("jdbc:sqlite:file:" + dbName + "?mode=memory&cache=shared") And then use WAL-mode by excute: "pragma journal_mode=WAL" I found that the memory size…
J.Div
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How to turn off WAL in hbase 2.0.0 with java API?

I wonder if there is any way to disable WAL (write ahead log) operations when inserting new data to a hbase table with JAVA API? Thank you for you help :)
rafik_bougacha
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WAL archiving in postgres is not working

I have enabled WAL archiving in postgres configuration file. When I restarted Postgres service WAL recovery is not working. There was no wal recovery entries in logs. Steps I followed: Created directory for wal: mkdir -p /var/lib/pgsql/wals/ mkdir…
Kiran
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data-wal is being filled when syncing data to SQLite DB

I have connected my device and accessed my applications data by going to /data/data/my.package.name/databases. Here I can see files: data data-shm data-wal As I can understand these files are specific to android system itself, but they represent…
Jonas
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HBASE Bulk load replication

We have a HBase based system where we would like to bulk load a few million rows on a daily basis in production. We think that HBase Bulk Load will be a good option compared to puts - the bulk load feature uses a MapReduce job to output table data…
Akshay Gehi
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Disable WAL in OrientDB through Java API

We have an OrientDB graph database and a daily scheduler which performs massive insertions in the database using the Java API. For this reason, we would like to disable WAL from the Java code when performing these insertions, otherwise the size of…
Alessandro Bardini
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PostgreSQL 9.6 wals management

I'm trying to understand my wals behavior on my PostgreSQL environment. My wal settings are : wal_keep_segments = 200 max_wal_size = 3GB min_wal_size = 80MB archive_command = 'cp %p /PostgreSQL-wal/9.6/pg_xlog/wal_archives/%f' archive_timeout =…
JeyJ
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Postgresql - What are the WAL filename limits?

Concerning postgresql WAL filename, what are the limits to the following? timeline xlog file segment My understanding is that segment is limited to 00..FF (boundary-inclusive). For instance, could the following WAL be produced by…
abstractx1
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PostgreSQL / WAL-archiving: can I leave archive_command empty when doing image snapshot backups?

I have a PostgreSQL 9.5 instance running off an Azure VM. As described here, I must specify a post- and a prescript to tell Azure: "Yes, I've taken care of putting the VM in a state, so the entire VM/blob can be backed up as a snapshot that can be…
Frederik Struck-Schøning
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postgresql: print transactions from WAL logs

I want to know if there is a way to read the transactions from WAL logs in a simpler way. I want the transactions not the binary data . I used pg_xlogdump but I have no idea how to get the transactions from the result which looked like this rmgr:…
SENTHIL VIDHIYAKAR S
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result of postgresql xlog dump

I am using PostgreSQL db in Ubuntu. I got to know about WAL logs and pg_xlogdump. I used pg_xlogdump to print the WAL logs on screen. But I have no idea how to interpret the response and to know what transactions were made.
SENTHIL VIDHIYAKAR S
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How to enable write ahead logging in FMDB iOS?

I wanna enable write ahead logging in FMDB. I am using objective c and iOS 8. Please help me.
reza_khalafi
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Disable WAL in influxdb v0.13 or force flush

I am trying to setup a simple cluster for influxdb on AWS using EFS (elastic file storage which is similar to NFS) where 2 different influx processes will share database. I have 2 EC2 instances (named: EC2_1, EC2_2) running their own influxdb…
Ashish C
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