Fix AV (0xC0000005) crash in seekdb background thread during JOIN query with multibyte characters (gb2312_cp932_sqlqa.euckr_other_scene_mysql)

[chyujing]

Environment

• Version: 5.7.25 OceanBase seekdb (r) (Built 1-1d32563d30803aee72e7ce1f61b690dddf6e66d5 Apr 3 2026)
• Is this an RD-provided temporary version?: No
• Reproducibility: Always reproducible (必现)

Description

During a mysqltest run for the gb2312_cp932_sqlqa.euckr_other_scene_mysql test case (around line 164), a JOIN query involving multibyte character columns causes the seekdb background thread to crash with an Access Violation (AV) error 0xC0000005 on Windows.

Steps to Reproduce

1. Connection String: mysql -uroot -h -P 2881
2. Reproducing SQL:

SELECT
    t1.id, HEX(t1.char_column), t1.char_column, t1.nchar_column,
    t1.varchar_column, t1.nvarchar_column, t1.text_column, t1.blob_column,
    t2.char_column, t2.varchar_column, t2.text_column, t2.blob_column
FROM db1.t1 t1, db1.t2 t2
WHERE t1.char_column = t2.char_column
ORDER BY id;

3. Associated Test Case: gb2312_cp932_sqlqa.euckr_other_scene_mysql
4. Client Symptom: Error 2013 (Lost connection to MySQL server during query).
5. Server Symptom: Access Violation 0xC0000005, READ access violation at an illegal address, stack trace in seekdb.exe, minidump generation failed.

Detailed mysqltest Reproduction Steps

1. Navigate to the directory: /obdata/data/AndroidTest/ob_opensource_test/tools/deploy
2. Execute the following commands:

export OCEANBASE_HOME=/obdata/data/AndroidTest/ob_opensource_test/
cd ${OCEANBASE_HOME}/tools/deploy
source activate_obd.sh
export OBD_SEEKDB_STATUS_FALLBACK_TCP=1

obd test mysqltest test_env --mysqltest-bin=${OCEANBASE_HOME}/deps/3rd/u01/obclient/bin/mysqltest --obclient-bin=${OCEANBASE_HOME}/deps/3rd/u01/obclient/bin/obclient --init-only --init-sql-dir=${OCEANBASE_HOME}/tools/deploy --init-sql-files='init.sql,init_user.sql|root@sys|test'
obd test mysqltest test_env --mysqltest-bin=${OCEANBASE_HOME}/deps/3rd/u01/obclient/bin/mysqltest --obclient-bin=${OCEANBASE_HOME}/deps/3rd/u01/obclient/bin/obclient --disable-reboot --test-set=gb2312_cp932_sqlqa.euckr_other_scene_mysql

Additional Information

• Environment Info: Please provide the connection strings for the problematic tenant and the sys tenant, as well as deployment information.
• Is the scene preserved?: (Not specified)
• Log Information: (Not provided)

Notes

This issue was reported from an external business side. Please select the appropriate "Work Item Type" based on the actual situation:

• Customer Service Feedback: Refers specifically to issues before production deployment or during POC, where a product bug is confirmed to require a fix and a new release.
• Online Issue: An issue that has occurred after production deployment, confirmed as a product bug, but not classified as a fault.
• Online Fault: An issue that has occurred after production deployment, confirmed as a product bug, and has caused business errors or public impact on the customer side (the interpretation of a fault belongs to the delivery service team).

[hnwyllmm]

Verified