Bug #15204 5.0 Crashes when selecting from imported data
Submitted: 23 Nov 2005 22:15 Modified: 2 Dec 2005 4:53
Reporter: Kolbe Kegel
Status: Closed
Category:Server Severity:S1 (Critical)
Version:5.0.16 OS:Linux (Linux)
Assigned to: Sergey Petrunia Target Version:

[23 Nov 2005 22:15] Kolbe Kegel 
Description:
Importing certain data from an SQL dump and executing certain queries against that data
can cause a crash.

How to repeat:
See private note.

Suggested fix:
n/a
[25 Nov 2005 10:32] Bugs System 
A patch for this bug has been committed. After review, it may
be pushed to the relevant source trees for release in the next
version. You can access the patch from:

  http://lists.mysql.com/internals/32703
[25 Nov 2005 21:34] Sergey Petrunia 
The fix has been pushed into 5.0.17 tree.

Description for the changelog:
Running a query could cause the server to crash if:

 * the query reads some table tbl and the optimizer was able to infer the condition in
form "tbl.f1 = c1 AND tbl.f2= c2 AND ... tbl.fN=cN" for table tbl.
 * table tbl has an index that covers fields {f1, ..., fN} and ref(c1, c2, ... cN); "using
index" can be used to access table tbl.
 * besides that, tbl has set of indexes, neither of which covers {f1,...fN} but taken
together they cover this set.
 * The record count estimates for accessing the table using the above indexes have some
particular values (the criteria is very difficult to formulate)

The fix is that such queries no longer crash the server.
[25 Nov 2005 21:36] Sergey Petrunia 
An error, in previous comment the passage
" * besides that, tbl has set of indexes, neither of which covers {f1,...fN} but
taken together they cover this set."

should be:

" * besides that, tbl has other indexes that cover some of {f1,...fN} fields."
[2 Dec 2005 4:53] Paul DuBois 
Noted in 5.0.17 changelog.