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Joël Cattin

pgBackRest – a simple privileges-related issue

By | Database Administration & Monitoring, Database management, Postgres | No Comments

I recently had to replace Barman by pgBackRest as Backup & Recovery solution for one of my customer. The purpose of this blog is not to show how I made the setup (some dbi blogs already exists for that), but only to share a small issue I encountered during the creation of the Stanza : [email protected]:/ [cms2] pgbackrest –stanza=cms2_primary stanza-create ERROR: [058]: version ’11’ and path ‘(null)’ queried from cluster do not match version ’11’…

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Franck Pachot

AWS Aurora vs. RDS PostgreSQL on frequent commits

By | AWS, Postgres | No Comments

This post is the second part of https://blog.dbi-services.com/aws-aurora-xactsync-batch-commit/ where I’ve run row-by-row inserts on AWS Aurora with different size of intermediate commit. Without surprise the commit-each-row anti-pattern has a negative effect on performance. And I mentioned that this is even worse in Aurora where the session process sends directly the WAL to the network storage and waits, at commit, that it is acknowledged by at least 4 out of the 6 replicas. An Aurora specific…

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Franck Pachot

AWS Aurora IO:XactSync is not a PostgreSQL wait event

By | AWS, Postgres | No Comments

By Franck Pachot . In AWS RDS you can run two flavors of the PostgreSQL managed service: the real PostgreSQL engine, compiled from the community sources, and running on EBS storage mounted by the database EC2 instance, and the Aurora which is proprietary and AWS Cloud only, where the upper layer has been taken from the community PostgreSQL. The storage layer in Aurora is completely different. In PostgreSQL, as in most RDBMS except for exclusive…

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Franck Pachot

ysql_bench: the YugaByteDB version of pgbench

By | Postgres | No Comments

By Franck Pachot . This follows the previous post on testing YugaByteDB 2.1 performance with pgbench: https://blog.dbi-services.com/yugabytedb-2-1/ A distributed database needs to reduce inter-node synchronization latency and then replaces two-phase pessimistic locking by optimistic concurrency control in many places. This means more serialization errors where a transaction may have to be re-tried. But the PostgreSQL pgbench does not have this possibility and this makes benchmarking distributed database very hard. For example when CERN tested CoackroachDB…

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Franck Pachot

How SQL Server MVCC compares to Oracle and PostgreSQL

By | Database Administration & Monitoring, Oracle, Postgres, SQL Server | One Comment

By Franck Pachot . Microsoft SQL Server has implemented MVCC in 2005, which has been proven to be the best approach for transaction isolation (the I in ACID) in OLTP. But are you sure that writers do not block readers with READ_COMMITTED_SNAPSHOT? I’ll show here that some reads are still blocked by locked rows, contrary to the precursors of MVCC like PostgreSQL and Oracle.

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Joël Cattin

From Oracle to Postgres with the EDB Postgres Migration Portal

By | Database Administration & Monitoring, Database management, Postgres | No Comments

EnterpriseDB is a valuable actor in PostgreSQL’s world. In addition to provide support, they also deliver very useful tools to manage easily your Postgres environments. Among these we can mention EDB Enterprise Manager, EDB Backup & Recovery Tool, EDB Failover Manager, aso… With this post I will present one of the last in the family, EDB Postgres Migration Portal, a helpful tool to migrate from Oracle to Postgres. To acces to the Portal, use your…

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Franck Pachot

pgSentinel: the sampling approach for PostgreSQL

By | Database Administration & Monitoring, Postgres | 9 Comments

By Franck Pachot . Here is the first test I did with the beta of pgSentinel. This Active Session History sampling is a new approach to Postgres tuning. For people coming from Oracle, this is something that has made our life a lot easier to optimize database applications. Here is a quick example showing how it links together some information that are missing without this extension.

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Franck Pachot

PGIO, PG_STAT_ACTIVITY and PG_STAT_STATEMENTS

By | Oracle, Postgres | One Comment

By Franck Pachot . For an Oracle DBA, we are used to join active sessions (from V$SESSION where status=’ACTIVE) with active statements (from V$SQL where users_executing>0) on the SQL_ID. V$ACTIVE_SESSION_HISTORY also displays the TOP_LEVEL_SQL_ID to get the entrypoint of the usercall if we need it. With Postgres it is a bit more difficult because it seems that PG_STAT_ACTIVITY do not show the active statement but only the top-level one. But pg_stat_statement collects statistics for the…

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Franck Pachot

Lighty for PostgreSQL

By | Database Administration & Monitoring, Postgres | No Comments

By Franck Pachot . If you follow this blog, you should know how I like Orachrome Lighty for Oracle, for its efficiency to monitor database performance statistics. Today Orachrome released the beta version of Lighty for Postgres: https://orachrome.com/news/la-beta-de-lighty-for-postgresql-est-ouverte/ The Cloud is perfect to do short tests with more resources than my laptop, especially the predictability of performance, then I started a Bitnami Postgres Compute service on the Oracle Cloud and did some tests with pgbench…

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