Request for REF_CURSOR type

[daviessm]

I have a program which iterates through millions of rows, some tables having ~50 columns and doing this through the existing functions seems to be quite slow when there are a lot of columns.

In a similar program written in Java I switched to using REF CURSORs through the JDBC driver and this drastically improved performance. I'd like to be able to use the same in Rust.

[kubo]

I tried it and it worked on my local machine. However it is dirty work. I cannot decide its API design now. Well, I'll decide it and release the next version within a few weeks.

[daviessm]

No rush from me. I'm doing this as a hobby project at the moment and trying to narrow down its performance issues. If you want to pre-release a test version I can give it a try.

[kubo]

I added REF_CURSOR support to the git master branch.

I have not written documents about it. oracle::sql_type::RefCursor type has four query methods. See this test code also.

Implicit statement results are also supported. See this doc comment.

[daviessm]

I was having a look at this this morning. I use r2d2-oracle for connection pooling and when I link that to 0.5.3-dev of rust-oracle (current git master) it complains about some async methods:

error[E0277]: `*mut oracle::binding::dpiConn` cannot be shared between threads safely
  --> src/lib.rs:76:5
   |
76 |     type Connection = oracle::Connection;
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `*mut oracle::binding::dpiConn` cannot be shared between threads safely
   | 
  ::: /home/steven/.cargo/registry/src/github.lhy31512.workers.dev-1ecc6299db9ec823/r2d2-0.8.9/src/lib.rs:72:22
   |
72 |     type Connection: Send + 'static;
   |                      ---- required by this bound in `r2d2::ManageConnection::Connection`
   |
   = help: within `oracle::connection::InnerConn`, the trait `Sync` is not implemented for `*mut oracle::binding::dpiConn`
   = note: required because it appears within the type `oracle::connection::InnerConn`
   = note: required because of the requirements on the impl of `Send` for `Arc<oracle::connection::InnerConn>`
   = note: required because it appears within the type `Connection`

error[E0277]: `*mut oracle::binding::dpiConn` cannot be sent between threads safely
  --> src/lib.rs:76:5
   |
76 |     type Connection = oracle::Connection;
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `*mut oracle::binding::dpiConn` cannot be sent between threads safely
   | 
  ::: /home/steven/.cargo/registry/src/github.lhy31512.workers.dev-1ecc6299db9ec823/r2d2-0.8.9/src/lib.rs:72:22
   |
72 |     type Connection: Send + 'static;
   |                      ---- required by this bound in `r2d2::ManageConnection::Connection`
   |
   = help: within `oracle::connection::InnerConn`, the trait `Send` is not implemented for `*mut oracle::binding::dpiConn`
   = note: required because it appears within the type `oracle::connection::InnerConn`
   = note: required because of the requirements on the impl of `Send` for `Arc<oracle::connection::InnerConn>`
   = note: required because it appears within the type `Connection`

error: aborting due to 2 previous errors

Is this an oversight or are changes needed to r2d2-oracle as well?

[kubo]

Thanks for the report. I'll fix it.

It is an incompatible change. The Connection struct implements Sync and Send at 0.5.2. However it doesn't at git master.

[kubo]

@daviessm
Fixed. Could you try the latest git master?

[daviessm]

Yes - I can use REF_CURSORs exactly as expected now, thanks. Happy to close this issue.

[kubo]

OK. I closed this issue.
The next version 0.5.3 will be released this weekend.

[kubo]

The next version 0.5.3 will be released this weekend.

It is postponed by one week. I'll change structs for lob locator types: oracle::sql_type::Clob and oracle::sql_type::Blob, which are new features in the next version.