| Bug #30597 | Change EXPLAIN output to include extrema of UNION components | ||
|---|---|---|---|
| Submitted: | 23 Aug 2007 14:16 | Modified: | 6 Jan 2011 2:35 |
| Reporter: | Baron Schwartz (Basic Quality Contributor) | Email Updates: | |
| Status: | Closed | Impact on me: | |
| Category: | MySQL Server: DML | Severity: | S4 (Feature request) |
| Version: | OS: | Any | |
| Assigned to: | Jørgen Løland | CPU Architecture: | Any |
| Tags: | qc explain | ||
[27 Aug 2007 11:34]
Valeriy Kravchuk
Thank you for a reasonable feature request.
[18 Aug 2010 9:01]
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/commits/116059 3220 Jorgen Loland 2010-08-18 Bug#30597: Change EXPLAIN output to include extrema of UNION components Previously, EXPLAIN of a large union would truncate the UNION RESULT row at the end of the list like this if the string got too large: <union1,2,3,4,...> With this patch, truncation happens in the middle of the string like this: <union1,2,3,...,9> This makes it easier to understand the boundaries of the UNION. @ mysql-test/r/explain.result Added test for BUG#30597 @ mysql-test/t/explain.test Added test for BUG#30597 @ sql/sql_lex.h Add inline function st_select_lex::last_select() @ sql/sql_select.cc Truncate UNION RESULT row of large UNIONs in the middle of the string instead of in the end
[25 Aug 2010 9:45]
Guilhem Bichot
approved, minor comments sent by mail
[26 Aug 2010 12:03]
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/commits/116857 3248 Jorgen Loland 2010-08-26 Bug#30597: Change EXPLAIN output to include extrema of UNION components Previously, EXPLAIN of a large union would truncate the UNION RESULT row at the end of the list like this if the string got too large: <union1,2,3,4,...> With this patch, truncation happens in the middle of the string like this: <union1,2,3,...,9> This makes it easier to understand the boundaries of the UNION. @ mysql-test/r/explain.result Added test for BUG#30597 @ mysql-test/t/explain.test Added test for BUG#30597 @ sql/sql_lex.h Add inline function st_select_lex::last_select() @ sql/sql_select.cc Truncate UNION RESULT row of large UNIONs in the middle of the string instead of in the end
[26 Aug 2010 12:03]
Jørgen Løland
Pushed to next-mr-bugfixing
[26 Aug 2010 13:55]
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/commits/116896 3250 Jorgen Loland 2010-08-26 Post-push fix for BUG#30597: Need to explicitly cast int argument to log10() to double on SPARC @ sql/sql_select.cc Cast int argument to log10() to double
[30 Aug 2010 8:33]
Bugs System
Pushed into mysql-next-mr (revid:alik@sun.com-20100830082745-n6sh01wlwh3itasv) (version source revid:alik@sun.com-20100830082745-n6sh01wlwh3itasv) (pib:21)
[13 Nov 2010 16:21]
Bugs System
Pushed into mysql-trunk 5.6.99-m5 (revid:alexander.nozdrin@oracle.com-20101113155825-czmva9kg4n31anmu) (version source revid:vasil.dimov@oracle.com-20100629074804-359l9m9gniauxr94) (merge vers: 5.6.99-m4) (pib:21)
[6 Jan 2011 2:35]
Paul DuBois
Noted in 5.6.1 changelog. Previously, EXPLAIN output for a large union truncated the UNION RESULT row at the end of the list as follows if the string became too large: <union1,2,3,4,...> To make it easier to understand the boundaries of the union, truncation now occurs in the middle of the string: <union1,2,3,...,9>
Description: In the EXPLAIN output of a large UNION, the UNION RESULT row in the output may not list all the items in the UNION. This makes it a little harder to understand the boundaries of the UNION. How to repeat: mysql> explain -> select 1 -> union all select 1 -> union all select 1 -> union all select 1 -> union all select 1 -> union all select 1 -> union all select 1 -> union all select 1 -> union all select 1 -> union all select 1 -> union all select 1 -> union all select 1 -> union all select 1 -> union all select 1 -> union all select 1 -> union all select 1 -> union all select 1 -> union all select 1 -> union all select 1 -> union all select 1 -> union all select 1 -> union all select 1 -> union all select 1 -> union all select 1 -> union all select 1 -> union all select 1 -> union all select 1 -> union all select 1 -> union all select 1 -> union all select 1 -> union all select 1 -> union all select 1 -> union all select 1 -> ; +----+--------------+---------------------------------------------------------------+------+---------------+------+---------+------+------+----------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+--------------+---------------------------------------------------------------+------+---------------+------+---------+------+------+----------------+ | 1 | PRIMARY | NULL | NULL | NULL | NULL | NULL | NULL | NULL | No tables used | ...snip... | 33 | UNION | NULL | NULL | NULL | NULL | NULL | NULL | NULL | No tables used | | NULL | UNION RESULT | <union1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,...> | ALL | NULL | NULL | NULL | NULL | NULL | | +----+--------------+---------------------------------------------------------------+------+---------------+------+---------+------+------+----------------+ 34 rows in set (0.00 sec) Suggested fix: I would prefer to truncate the middle and list the beginning and end with dots in between. The code in question is in sql_select.cc, in select_describe(): 14210 memcpy(table_name_buffer, STRING_WITH_LEN("<union")); 14211 for (; sl && len + lastop + 5 < NAME_LEN; sl= sl->next_select()) 14212 { 14213 len+= lastop; 14214 lastop= my_snprintf(table_name_buffer + len, NAME_LEN - len, 14215 "%u,", sl->select_number); 14216 } 14217 if (sl || len + lastop >= NAME_LEN) 14218 { 14219 memcpy(table_name_buffer + len, STRING_WITH_LEN("...>") + 1); 14220 len+= 4; 14221 } I'm not a good C coder, so I don't know what's a good patch, but I'd like to see this output: <union1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,...33>