>> Prepared statements will automatically be created for any queries where it can be inferred that the query is static
What does this mean in practice? Like, actual prepared statements are created against the DB session if there are no bound variables, even if that query is only made once?
If so, it's an interesting but highly opinionated approach...
If you're using parameterized queries, then you _have_ to use PostgreSQL's "Extended Query" flow, which is what most people would think of as a "prepared statement". This is hardly opinionated.
But normally, you use an unnamed prepared statement and/or portal, which PG will clean up for you, essentially only letting you have one of those per session (what we think of as a connection).
I agree that sentence didn't make any sense. So I looked at the code (1) and what they mean is that they'll use a named prepared statement automatically, essentially caching the prepared statement within PG and the driver itself. They create a signature for the statement. I agree, this is opinionated!
In most SQL databases, once you have a connection handle, you can allocate an arbitrary number of statement handles, and each SQL "statement" can be executed independently, has an associated query, parameters, a result set, and so on.
It is entirely ordinary with an API like that to prepare a statement, bind parameters and columns, and execute and fetch the results. You can then reuse a statement in its prepared state, but usually with different parameter values, as many times as you want within the same session.
The performance advantage of doing this for non-trivial queries is so substantial that many databases have a server side parse cache that is checked for a match even when a client has made no attempt to reuse a statement as such. That is easier if you bind parameters, but it is possible for a database to internally treat all embedded literals as parameters for caching purposes.
Thanks... I haven't got the mental energy to follow their code ATM but yeah, it seems weird to buffer a static query as a prepared statement if it's only going to be used once.
Maybe that kind of goes with a Nodejs philosophy, though? It seems like an assumption that in most cases a static query will recur... and maybe that's usually accurate with long running persistent connections. I'm much more used to working in PHP and not using persistent connections, and so sparing hitting a DB with any extra prepare call if you don't have to, unless it's directly going to benefit you later in the script.
I believe it's typical for database libraries with auto-prepare to also have batch statement sending (and use it for prepare-executes), so there's no real cost to doing the prepare. The database has to parse/plan the statement regardless, and there's no round-trip delay with statement batching.
my own, very opinionated way of doing this in nodejs was to wrap node-mysql in promises and then force myself to make it explicit when preparing a a query whether I want it to set up a prepared statement which returns a reusable handle or run directly. That requires tracking prepared statement names and key/values for each one.
you'll probably find this bad code too, but it was more of an experiment... I still don't feel safe using nodejs in deployment.
Postgres supports 2 types of prepared statements - "generic" prepared statements (which can accept parameters) and "custom" which are prepared for a specific execution so bake the parameters in.
What does this mean in practice? Like, actual prepared statements are created against the DB session if there are no bound variables, even if that query is only made once?
If so, it's an interesting but highly opinionated approach...