MySQL Bugs: #87842: Typo in temptable_max

Bug #87842	Typo in temptable_max_ram description
Submitted:	22 Sep 2017 14:44	Modified:	2 Nov 2017 18:28
Reporter:	Alexey Kopytov	Email Updates:
Status:	Closed	Impact on me:	None
Category:	MySQL Server: Documentation	Severity:	S3 (Non-critical)
Version:	8.0	OS:	Any
Assigned to:		CPU Architecture:	Any

Description:
Description for the temptable_max_ram system variable in the manual says: "Defines the maximum amount of memory that the TempTable storage engine can use before data is stored to disk. The default value is 1073741824 bits (1GiB)." https://dev.mysql.com/doc/refman/8.0/en/server-system-variables.html#sysvar_temptable_max_...

I guess it means to say "bytes" instead of "bits".

How to repeat:
See above.

Thank you for the bug report.

Posted by developer:
 
The values in the docs are as given in the specification (bits).

Paul,

I'm not sure what specification you were referring to, but it contradicts a number of things:

- the description in "mysqld --help":

static Sys_var_ulonglong Sys_temptable_max_ram(
       "temptable_max_ram",
       "Maximum amount of memory (in bytes) the TempTable storage engine is "
       "allowed to allocate from the main memory (RAM) before starting to "
       "store data on disk.",

- source code, for example, the following code in
  storage/temptable/include/temptable/allocator.h clearly indicates the
  amount is in bytes, rather than bits:

  if (bytes_allocated_in_ram > temptable_max_ram) {
    t = Mem_type::DISK;
  } else {
    ...
  }

- the ISO/IEC 80000 standard defining "GiB" as the unit symbol for
  "Gibibyte", whereas "Gibibit" has the unit symbol of "Gibit".

- last, but not least, the tradition to specify amounts of memory in
  bytes rather than bits

Posted by developer:
 
The temptable_max_ram default value is in fact 1073741824 bytes. My error. 

Thank you for the bug report.

The documentation has been updated.
Thank you for the bug report.