CalvinKirs opened a new pull request, #67520:
URL: https://github.com/apache/doris/pull/67520
### What problem does this PR solve?
Issue Number: None
Problem Summary:
After CLIENT_DEPRECATE_EOF support was enabled by #61050 and backported by
#61062, Connector/J 8.x with useCursorFetch=true can hang when a
server-prepared statement returns an empty result set.
Connector/J versions before 9.5 consume the first OK packet after column
definitions while probing whether a requested server cursor was created. Doris
does not create a server cursor. With CLIENT_DEPRECATE_EOF negotiated, an empty
result has no metadata terminator, so its only result-set end packet is
consumed by the cursor probe and the client waits indefinitely for another
packet.
This also explains the observed version difference: releases that do not
advertise CLIENT_DEPRECATE_EOF still send the metadata EOF, so the final
result-set marker remains available.
### What is changed?
- Parse CURSOR_TYPE_READ_ONLY from COM_STMT_EXECUTE.
- Preserve the cursor-fetch request when execution is forwarded between FEs.
- For affected Connector/J versions (8.x and 9.0 through 9.4) that negotiate
CLIENT_DEPRECATE_EOF, send a compatibility metadata terminator so the real
final marker is not consumed.
- Keep Connector/J 9.5+ and other clients on the standard
CLIENT_DEPRECATE_EOF path.
- Add unit and regression coverage for empty and non-empty cursor-fetch
results.
### Release note
Fix empty prepared-statement results hanging with MySQL Connector/J 8.x when
cursor fetching is enabled.
### Check List (For Author)
- Test:
- Unit Test:
StmtExecutorTest#testCursorFetchMetadataTerminatorDependsOnConnectorJVersion
- Regression test: prepared_stmt_p0/test_cursor_fetch_empty_result
- Manual test: official Connector/J 8.2.0 and 9.5.0 with empty and
non-empty results, with useCursorFetch enabled and disabled
- Build: ./build.sh --fe
- Behavior changed: Yes. A compatibility metadata terminator is sent only
for affected Connector/J cursor requests when CLIENT_DEPRECATE_EOF is
negotiated.
- Does this need documentation: No
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