---
title: "#227: A Postgres Concurrency Deep Dive"
publication: "Postgres Weekly"
issue: 227
published_at: "2017-10-04"
canonical_url: "https://postgresweekly.com/issues/227"
---

Postgres Weekly 227   . 

[Read this on the Web](http://postgresweekly.com/issues/227) 

[Postgres Weekly](http://postgresweekly.com) Issue 227 — October 4, 2017     

[A Deep Dive into Postgres Concurrency](https://www.youtube.com/watch?v=ZxhBkBNxvR0&utm_source=postgresweekly&utm_medium=email)An easy to follow 50 minute talk from PostgresOpen Silicon Valley 2017 on different forms of concurrency and how Postgres works with them. Tejas Manohar#video [Fermi Estimates on Postgres Performance](https://www.citusdata.com/blog/2017/09/29/what-performance-can-you-expect-from-postgres/?utm_source=postgresweekly&utm_medium=email)A simplified guide for what you should expect in terms of the read performance and ingest performance for queries in Postgres. Samay Sharma [2ndQuadrant PostgreSQL Conference - Schedule Out Now](http://www.2qpgconf.com)2Q PGConf is dedicated to exchanging & increasing knowledge about PostgreSQL. Join us for this unique opportunity taking place in NYC & Chicago to learn more about recent achievements and exciting future developments in PostgreSQL from world-class experts. 2ndQuadrant PostgreSQL Events#sponsored[![\](https://copm.s3.amazonaws.com/05bf9481.jpg)](http://www.2qpgconf.com) [Locking Down Permissions in Postgres and on Redshift](https://blog.dbrhino.com/locking-down-permissions-in-postgresql-and-redshift.html?utm_source=postgresweekly&utm_medium=email#locking-down-permissions-in-postgresql-and-redshift)Users are automatically granted permissions due to their membership in a built-in role called `PUBLIC`. Buck Ryan [Swap Two Column Values in SQL](https://hashrocket.com/blog/posts/swap-two-column-values-in-sql-part-1?utm_source=postgresweekly&utm_medium=email)Want to swap the order of a few columns without having to drop/remove or re-write the whole table? [Part 2 here.](https://hashrocket.com/blog/posts/swap-two-column-values-in-sql-part-2) Josh Branchaud [Getting Started with pgRouting to Create Location Paths](https://www.compose.com/articles/geofile-getting-started-with-pgrouting/?utm_source=postgresweekly&utm_medium=email)pgRouting is useful if you’re already using PostGIS. It can be handy for helping find various paths and routes between locations, here’s a primer on getting started with it. Compose [A Look at PERCENT_RANK vs CUME_DIST](https://momjian.us/main/blogs/pgblog/2017.html?utm_source=postgresweekly&utm_medium=email#October_2_2017)`cume_dist` computes the %age of rows that are ‘less than or equal,’ while `percent_rank` computes those that are ‘less than’ the current row, except it also assumes the current row isn’t in the partition. Bruce Momjian [Understanding Caching in Postgres - An In-Depth Guide](https://madusudanan.com/blog/understanding-postgres-caching-in-depth/?utm_source=postgresweekly&utm_medium=email)A golden oldie from last year that might be worth revisiting. Madusudanan B N [pglogical and Postgres 10 Partitions](https://blog.2ndquadrant.com/pg-phriday-pglogical-postgres-10-partitions/?utm_source=postgresweekly&utm_medium=email)A look at Postgres 10’s logical replication and partitioning support, how it plays with pglogical, and how it’s still evolving. 2ndQuadrant [Using the Invisible 'xmin' Column in Queries](https://momjian.us/main/blogs/pgblog/2017.html?utm_source=postgresweekly&utm_medium=email#October_4_2017)Select for update is usually what you want when grabbing a value that you’re going to update right after, but here we see where using `xmin` could be a valid approach. momjian.​us [Linux cloud hosting starting at 1GB of RAM for $5/mo](https://welcome.linode.com/postgres-weekly/?utm_source=cooperpress&utm_medium=sponsored&utm_campaign=postgres-weekly-sponsored)Get a Linode server up and running in seconds. Get a $20 credit on a new account. Linode Cloud Hosting#sponsored [PGAudit: An Auditing Extension for Postgres](https://www.pgaudit.org/?utm_source=postgresweekly&utm_medium=email)Provides the tools needed to produce audit logs required to pass government, financial, or ISO certification audits. PostgreSQL Global Development Group#tools    

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