feat: remove prepare operation in copy from

[KennyChenFight]

I think it's not necessary to use prepare operation to set value type before copy from operation. It would produce one RTT and slow down copy from operation.

[jackc]

I think that step is necessary to handle native Go values like string and int32...

[mixmind]

I have same question,

I'm using extension(pipelinedb), there is no simple select from table that pgx tries to prepare statement.
This extension creates foreign table and simple select from it can only throw error, that it's stream and not a table.
This table only in use for inserts, or creating view from it.

Removing prepare statements would help for me too.
Can you please suggest some workaround , that I could use COPY too?

[jackc]

@mixmind You could drop down to the pgconn level and construct the copy stream manually. See https://pkg.go.dev/github.com/jackc/pgconn#PgConn.CopyFrom.

[bfontaine]

@KennyChenFight any thought on Jack’s comment?

[alejandrodnm]

Hi @jackc we are using CopyFrom in a write intensive application. I wanted to get rid of the prepare statement, would you accept a PR that exposes a new CopyFromWithStatementDescription method that accepts a pgconn.StatementDescription as argument?

[jackc]

@alejandrodnm I don't mind an improvement to copy from performance, but I'm not convinced that a CopyFromWithStatementDescription is the correct approach.

What about CopyFrom using the automatic statement or description caching like Query does? Then everyone would benefit automatically. Detecting / handling schema changes might be tricky though.

[alejandrodnm]

Sounds good @jackc , I'll give it a try.

Thanks

[alejandrodnm]

@jackc I created PR #1412 for what we discussed