PostgreSQL

Postgres, the fsync() issue, and ‘pgio’ (the SLOB method for PostgreSQL)

By Franck Pachot . That's a long blog post title, which is actually just a good pretext to play with Kevin Closson SLOB method for PostgreSQL: pgio I use the beta version of pgio here. If you want to read(…)

PostgreSQL – logical replication with pglogical

Although PostgreSQL 10 integrate native logical replication (have a look here or here), it is always interesting to be aware of alternative solutions to the available in-core features. One of those is called(…)

Full page logging in Postgres and Oracle

By Franck Pachot . In my opinion, the volume of logging (aka redo log, aka xlog, aka WAL) is the most important factor for OLTP performance, availability and scalability, for several reasons: This is the only structure where disk latency(…)

Server process name in Postgres and Oracle

By Franck Pachot . Every database analysis should start with system load analysis. If the host is in CPU starvation, then looking at other statistics can be pointless. With ‘top’ on Linux, or equivalent such as process explorer on(…)

Postgres vs. Oracle access paths XI – Sample Scan

By Franck Pachot . I was going to end this series with the previous post because the last access path available in Postgres is a bit special: a Seq Scan that returns only a sample of(…)

Postgres vs. Oracle access paths X – Update

By Franck Pachot . In the previous post we have seen the cheapest way to get one row, reading only one block from its physical location. But that's the optimal case where the row has not(…)

Postgres vs. Oracle access paths IX – Tid Scan

By Franck Pachot . In the previous post we have seen how Postgres and Oracle finds the table row from the index entry. It uses the TID / ROWID. I’ll focus on this access path(…)

Postgres vs. Oracle access paths VIII – Index Scan and Filter

By Franck Pachot . In the previous post we have seen a nice optimization to lower the consequences of bad correlation between the index and the table physical order: a bitmap, which may include false positives(…)

Postgres vs. Oracle access paths VI – Index Scan

By Franck Pachot . In the previous post my queries were still reading the indexed column only, from a table which had no modifications since the last vacuum, and then didn't need to read table pages:(…)

Postgres vs. Oracle access paths V – FIRST ROWS and MIN/MAX

By Franck Pachot . We have seen how an index can help to avoid a sorting operation in the previous post. This avoids a blocking operation: the startup cost is minimal and the first rows can(…)