Aleph Technologies Blog

Applications come and go, data stays.

Resync postgresql standby with wal-g catchup

When a postgresql standby gets out of sync and the replication lag is relatively big, the usual solution is to clone the primary database again, to avoid the slow proess of re-applying all archived WALs that are lagging. However, a complete clone of a large database could be long. As I wondered the other time how I could do the same technique as for Oracle databases: identify the current SCN on the physical.. Read More

Postgresql Performance on Ubuntu linux 18.04 and Amazon AWS EC2 iXL instance

Introduction This is a follow-up on our Postgresql Performance on Ubuntu 18.04 and Nutanix post. We document here the same pgbench tests on an Amazon EC2 i-XL instance with NVMe SSD storage. Disclaimer The following test results are not intended to give definitive numbers on the tested platform. These are only illustrative of the methodology used to test the platform for postgresql workloads. Sustained database benchmark with different linux kernel parameters We tested.. Read More

Postgresql Performance on Ubuntu linux 18.04 and Nutanix

Background On november 4, 2019, we were benchmarking a number of virtual machines on a new 12-node DELL 740XD-24 appliance under Nutanix AHV (and RDMA enabled). I was getting weird results and I tweeted the following: At the moment we were configuring both the Nutanix appliance and the Linux kernel parameters most suitable for a postgresql 9.5 specific workload. That was not a good idea and produced confusing test results since the actual.. Read More

GDPR article mapping to RDBMs feature availability

To close the article series on GDPR and available features in each of the four database systems reviewed, I was made aware by a few acquaintances that a more clear mapping between the actual regulation text and the itentified tasks, along with the features available on each database system would be very helpful. This is the purpose of this article and I hope it will be of help to everyone trying to map.. Read More

GDPR demystified – Part 3 : Postgresql

In the previous posts, we discussed GDPR and how we could enforce it in the scope of Oracle¬† and SQL Server databases. We now cover the same topic with Postgresql databases in mind. As always, please refer to GDPR Data Security requirements laid down in the initial post. We will continue to walk the same task and activity structure for all RDBMs we cover. Let’s go to the identified GDPR tasks and requireements.. Read More

Improving fuzzy searches in postgresql with pg_trgm

I have been researching postgresql search capabilities for quite a while. Besides the very powerful Full Text Search capabilities the engine offers today, there are a few less known index types that support string searches in the form : where foo like ‘%bar%’ For these cases, a regular b-tree index on ‘foo’ is guaranteed to never be used. The following example illustrates a case in which a relatively simple query is transformed to.. Read More