Uploaded image for project: 'MariaDB Server'
  1. MariaDB Server
  2. MDEV-7662

Possible perf issue: handler objects are created for merged derived tables

        Details

        • Type: Bug
        • Status: Open
        • Priority: Minor
        • Resolution: Unresolved
        • Affects Version/s: 10.0.17, 5.5.42
        • Fix Version/s: 10.1
        • Component/s: Optimizer
        • Labels:
          None

          Description

          This is a continuation of MDEV-7586.

          If one takes a basic testcase with a merged derived table (or a view):

          create table t2 (a int);
insert into t2 values (1),(2),(3);
create view v2 as select a from t2;

select * from v2;

          they can see that the code calls create_tmp_table(... do_not_open=true. ...) for the derived table (or the merged view). This may add extra overhead (although we are not sure how much ATM).

          This effect was introduced in MariaDB 5.3, in this commit:

          igor@askmonty.org-20100526201818-en2jqo1p1t3hi3ra
Igor Babaev <igor@askmonty.org>
maria-5.3-mwl106
Wed 2010-05-26 13:18:18 -0700
MWL#106: Backport optimizations for derived tables and views.
The main consolidated patch.

          MySQL 5.6 doesn't have this optimization, so they dont have this problem.

            Gliffy Diagrams

              Attachments

                Issue Links

                relates to

                Bug - A problem which impairs or prevents the functions of the product. MDEV-7586 Merged derived tables/VIEWs increment created_tmp_tables

                • Critical - Crashes, loss of data, severe memory leak.
                • Closed

                  Activity

                  There are no comments yet on this issue.

                    People

                    • Assignee:
                      psergey Sergei Petrunia
                      Reporter:
                      psergey Sergei Petrunia
                    • Votes:
                      0 Vote for this issue
                      Watchers:
                      1 Start watching this issue

                      Dates

                      • Created:
                        Updated: