supabase / supavisor / 17412897580

65%

Build Type

push

github

Committed by web-flow

Commit Message

feat: improved named prepared statements support (#694)

Adds support for Prepared Statements through the Extended Query
Protocol.

### Concept
This PR implements the following architecture:
- ClientHandlers keep track of the prepared statements sent on them
- ClientHandlers update the prepared statement packets changing the
statement names to "internal names" (this is necessary because clients
may reuse the names in different connections)
- Prepared statement packets aren't sent directly to the db socket, but
instead are sent to the DbHandler. Whenever the ClientHandler sends a
`bind` packet to the DbHandler, it should also send the respective
`parse` (which it has stored)
- DbHandler decides whether it needs to run "parse" or just "bind"
- DbHandler must intercept "parse" responses when the client didn't
request them/it was made due to necessity
- DbHandler injects "parse" responses when the client requested a parse
but it's not necessary

### Parsing/decoding
- To be able to handle the prepared statement packets, ClientHandlers
need to peek at every client packet (at least on transaction mode)
- To be able to intercept parse responses, DbHandler needs to peek at
every server packet.
- For both ClientHandler and DbHandler, we can avoid decoding the whole
payload/decode only what's necessary (generally, we only need tagging,
except for the prepared statement payloads from which we need more
data).
- The decoding means more CPU usage, and it could also mean that we will
need to optimize the decoding routines a bit further.

### Limits
- ClientHandlers and DbHandler have separate limits
- If trespassing a ClientHandler limit, an error is returned and the
connection is closed
- If trespassing the DbHandler limit, a clean-up is triggered and a
random set of prepared statements is dropped. This is transparent to the
client. The only consequence for them is that some of their queries may
need to be re-prepared.
- ClientHandler has a memory limit. Every cli... (continued)

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356 of 438 new or added lines in 17 files covered. (81.28%)

14 existing lines in 4 files now uncovered.

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