MySQL Bugs: #99339: .idb grows indefenitely (Bug #96466 with REPLACE)

Bug #99339	.idb grows indefenitely (Bug #96466 with REPLACE)
Submitted:	23 Apr 2020 20:22	Modified:	11 Jun 2020 18:01
Reporter:	G S	Email Updates:
Status:	Closed	Impact on me:	None
Category:	MySQL Server: InnoDB storage engine	Severity:	S2 (Serious)
Version:	8.0.19	OS:	Red Hat
Assigned to:		CPU Architecture:	x86
Tags:	regression

Description:
It is almost the same bug as described in #96466. We have upgraded our database to MySQL 8.0.19. The tables have at least one column with a mediumBLOB type. Since the upgrade, the .idb files keep increasing despite the number of lines in the tables are still the same. 

How to repeat:
Settings - 
innodb_file_per_table=ON

Same conditions as in #96466, but with REPLACE queries instead of UPDATE.

In production, we're keeping replacing lines with the REPLACE command. Each table has a maximum number of lines and works like a circular buffer. (Use of a modulo in a stored procedure)

=>The disk is full in one day. The use of the OPTIMIZE command is out of question.

Workaround:
Change  "REPLACE INTO.." query into "INSERT INTO ...ON DUPLICATE UPDATE..."

Suggested fix:
#96466 is fixed for UPDATE but not for REPLACE. Release the data when REPLACE is used for the same key.

Hello!

Thank you for the report and feedback.
Verified as described.

regards,
Umesh

Posted by developer:
 
Fixed as of the upcoming 8.0.21 release, and here's the proposed changelog entry from the documentation team:

The lob::purge() function did not free LOBs correctly for an undo log
record type (TRX_UNDO_UPD_DEL_REC) that is generated when an insert
operation modifies a delete-marked record.