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amitlan | 5 years ago | on: Ask HN: What NoSQL database do you recommend in 2020?

Postgres core hackers are working to ease the limit on max allowable concurrent connections, for example:

https://www.postgresql.org/message-id/flat/20200301083601.ew...

Maybe the proposal above by itself isn't enough, but it's going to solve some of the many problems that put a restriction on max allowable connections in the first place. For example, I am not sure if there is anything in there to reduce the baseline per connection memory consumption, but maybe that will come up as the next problem to solve and will hopefully be solved sooner than later.

amitlan | 6 years ago | on: PostgreSQL 12

Today's news is about PostgreSQL 12 GA release. The news you may have seen recently was about few Beta releases in last few months and an RC release last week.

amitlan | 7 years ago | on: PostgreSQL 11 Released

The documentation of creating partitions [1] says this:

"When creating a hash partition, a modulus and remainder must be specified. The modulus must be a positive integer, and the remainder must be a non-negative integer less than the modulus. Typically, when initially setting up a hash-partitioned table, you should choose a modulus equal to the number of partitions and assign every table the same modulus and a different remainder (see examples, below). However, it is not required that every partition have the same modulus, only that every modulus which occurs among the partitions of a hash-partitioned table is a factor of the next larger modulus. This allows the number of partitions to be increased incrementally without needing to move all the data at once. For example, suppose you have a hash-partitioned table with 8 partitions, each of which has modulus 8, but find it necessary to increase the number of partitions to 16. You can detach one of the modulus-8 partitions, create two new modulus-16 partitions covering the same portion of the key space (one with a remainder equal to the remainder of the detached partition, and the other with a remainder equal to that value plus 8), and repopulate them with data. You can then repeat this -- perhaps at a later time -- for each modulus-8 partition until none remain. While this may still involve a large amount of data movement at each step, it is still better than having to create a whole new table and move all the data at once."

[1] https://www.postgresql.org/docs/current/static/sql-createtab...

amitlan | 9 years ago | on: Implement table partitioning

Note that there is no shorthand syntax (yet), where you define a partitioned schema in just one line of DDL.

As of now, you still need to create the root partitioned table as one command specifying the partitioning method (list or range), partitioning columns (aka PARTITION BY LIST | RANGE (<columns>)) and then a command for every partition specifying the partition bounds. No triggers or CHECK constraints anymore though. Why that way? Because we then don't have to assume any particular use case, for which to provide a shorthand syntax -- like fixed width/interval range partitions, etc.

That said, having the syntax described at the beginning of the last paragraph in the initial version does not preclude offering a shorthand syntax in later releases, as, and if we figure out that offering some such syntax for more common use cases is useful after all.

amitlan | 9 years ago | on: Implement table partitioning

Yes, it is not possible to optimize (ie, prune useless partitions for quicker access) the query select * from tab where key = x. You'd need actual hash partitioning for that. The mechanism Postgres uses to perform partition-pruning (constraint exclusion) does not work for the hashing case.

amitlan | 9 years ago | on: Implement table partitioning

Not natively, as in there is no PARTITION BY HASH (<list-of-columns>). What limitations do you face when trying to roll-your-own hash partitioning using check constraints (in 9.6)?

amitlan | 10 years ago | on: Jepsen: Distributed Systems Safety Analysis

Not quite sure whether something like multixact data corruption is symptomatic of the kind of underlying issues in database system implementations that Jepsen is after. I may be wrong though.
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