Foreign tables have been a headline feature of Postgres ever since the release of version 9.2. Combined with extensions, they’re the secret sauce that allows Postgres to pull data from other database engines, flat files, REST interfaces, and possibly every gas station, residence, warehouse, farmhouse, hen house, outhouse, and doghouse in the area. But that kind of power comes at a significant cost. Since the remote data comes from what is essentially a black box, there are a lot of performance optimizations Postgres can’t apply.
I always advocate breaking up large Postgres tables for a few reasons. Beyond query performance concerns, maintaining one monolithic structure is always more time consuming and consequentially more dangerous. The time required to create a dozen small indexes may be slightly longer than a single larger one, but we can treat the smaller indexes as incremental. If we want to rebuild, add more indexes, or fix any corruption, why advocate an all-or-nothing proposition?
The Postgres developers recently announced the availability of the first public beta for Postgres 9.6. I would be highly remiss to ignore such an opportunity to dig into any interesting functionality listed in the 9.6 release notes. All in all, it’s a pretty exciting series of advancements, and assuming this is a glimpse of what we see when 9.6 drops, I’d say we’re on the right track. Plentiful Parallelism Probably the most high-profile addition for 9.
I recently noted that the COPY command in Postgres doesn’t have syntax to skip columns in source data when importing it into a table. This necessitates using one or more junk columns to capture data we’ll just be throwing away. During that, I completely forgot that friendly devs had contributed alternative file handling methods as Foreign Data Wrappers. Most people think of foreign wrappers as a method for interacting with remote databases.