DapperLib / DapperLib/Dapper

Bad performance when reading CLOBs on Oracle

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#546 6 comments 1 reaction 0 assignees View on GitHub

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area:settings db:oracle
Dominant language
C#
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Description

Currently dapper is setting InitialLongFetchSize to -1 if the command supports it in order to avoid the n+1 problem when reading LONG columns from a database like Oracle. It would be great if it could also set InitialLOBFetchSize to -1 as well. Currently my performance is horrible when reading a query returning CLOB.

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  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start by tracing where command support for InitialLongFetchSize is checked and how that setting is applied for Oracle reads. Investigate whether InitialLOBFetchSize can be configured in the same entry point, then verify that CLOB queries avoid the reported performance problem and add or update coverage if the relevant test location is found.

Written by the indexing model from the issue text.

Assessment

Tech stack
csharp, sql
Domain
databases
Issue type
Bug
Difficulty
3/5
Estimated time
1-2 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
38/100

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