Request for setting statement properties ROW_PREFETCH and LOBPREFETCH_SIZE

[daviessm]

I would like to be able to set the properties DEFAULT_LOBPREFETCH_SIZE and DEFAULT_ROW_PREFETCH when connections are created (incl. pooled connections from r2d2_oracle): https://docs.oracle.com/cd/E18283_01/appdev.112/e10646/ociaahan.htm#sthref5292

[daviessm]

LOBPREFETCH_SIZE isn't yet implemented in ODPI-C, I've requested it here: oracle/odpi#163

[kubo]

In oracle/odpi#163 (comment)

I'll add Statement.define() to rust-oracle.

I didn't after I thought about use cases. Instead, I changed the type for LOB columns to string to follow @anthony-tuininga's suggestion.

[anthony-tuininga]

Returning CLOBs as strings and BLOBs as bytes (whatever those are called in Rust!) makes good sense. There may still be occasions, however, where you want to return the LOB -- for those cases where you have a LOB that won't fit in memory and you want to only read or write portions of it at a time. Those situations are rare, but definitely exist!

[kubo]

@anthony-tuininga I agree with you.

I have a plan to support reading and writing portions of LOBs. I did it two month ago in my local repository excluding documentation and small tweaks. When I make it public, I'll add a statement parameter to get LOB column data as Lob data types. I thought that they were rare so LOB data are got as strings or bytes by default.

[daviessm]

Resolved with 7ec5577 - configurability of ROW_PREFETCH; and d29652c - directly access CLOBs as Strings and BLOBs as bytes

[kubo]

FYI though the following may be unnecessary by d29652c.

I added Connection::set_oci_attr corresponding to dpiConn_setOciAttr, which sets OCI handle attributes to connections.
I also added types corresponding to some OCI handle attributes, including DEFAULT_LOBPREFETCH_SIZE. See here.

Note: Connection::set_oci_attr may be changed to unsafe function later.