Window Functions code tries to minimize the number of times it
needs to sort the select's resultset by finding "compatible"
OVER (PARTITION BY ... ORDER BY ...) clauses.
This employs compare_order_elements(). That function assumed that
the order expressions are Item_field-derived objects (that refer
to a temp.table). But this is not always the case: one can
construct queries order expressions are arbitrary item expressions.
Add handling for such expressions: sort them according to the window
specification they appeared in.
This means we cannot detect that two compatible PARTITION BY clauses
that use expressions can share the sorting step.
But at least we won't crash.
from view
A crash of the server happened when executing a stored procedure whose the
only query calculated window functions over a mergeable view specified
as a select from non-mergeable view. The crash could be reproduced if
the window specifications of the window functions were identical and both
contained PARTITION lists and ORDER BY lists. A crash also happened on
the second execution of the prepared statement created for such query.
If to use derived tables or CTE instead of views the problem still
manifests itself crashing the server.
When optimizing the window specifications of a window function the
server can substitute the partition lists and the order lists for
the corresponding lists from another window specification in the case
when the lists are identical. This substitution is not permanent and should
be rolled back before the second execution. It was not done and this
ultimately led to a crash when resolving the column names at the second
execution of SP/PS.
main.derived_cond_pushdown: Move all 10.3 tests to the end,
trim trailing white space, and add an "End of 10.3 tests" marker.
Add --sorted_result to tests where the ordering is not deterministic.
main.win_percentile: Add --sorted_result to tests where the
ordering is no longer deterministic.
Users expect window functions to produce a certain ordering of rows in
the final result set. Although the standard does not require this, we
already have the filesort result done for when we computed the window
function. If there is no ORDER BY attached to the query, just keep it
till the SELECT is completely evaluated and use that to print the
result.
Update test cases as many did not take care to guarantee a stable
result.
The syntax error happened because we had not implemented a different print for
percentile functions. The syntax is a bit different when we use percentile functions
as window functions in comparision to normal window functions.
Implemented a seperate print function for percentile functions
- Added sql/mariadb.h file that should be included first by files in sql
directory, if sql_plugin.h is not used (sql_plugin.h adds SHOW variables
that must be done before my_global.h is included)
- Removed a lot of include my_global.h from include files
- Removed include's of some files that my_global.h automatically includes
- Removed duplicated include's of my_sys.h
- Replaced include my_config.h with my_global.h
Benefits of this patch:
- Removed a lot of calls to strlen(), especially for field_string
- Strings generated by parser are now const strings, less chance of
accidently changing a string
- Removed a lot of calls with LEX_STRING as parameter (changed to pointer)
- More uniform code
- Item::name_length was not kept up to date. Now fixed
- Several bugs found and fixed (Access to null pointers,
access of freed memory, wrong arguments to printf like functions)
- Removed a lot of casts from (const char*) to (char*)
Changes:
- This caused some ABI changes
- lex_string_set now uses LEX_CSTRING
- Some fucntions are now taking const char* instead of char*
- Create_field::change and after changed to LEX_CSTRING
- handler::connect_string, comment and engine_name() changed to LEX_CSTRING
- Checked printf() related calls to find bugs. Found and fixed several
errors in old code.
- A lot of changes from LEX_STRING to LEX_CSTRING, especially related to
parsing and events.
- Some changes from LEX_STRING and LEX_STRING & to LEX_CSTRING*
- Some changes for char* to const char*
- Added printf argument checking for my_snprintf()
- Introduced null_clex_str, star_clex_string, temp_lex_str to simplify
code
- Added item_empty_name and item_used_name to be able to distingush between
items that was given an empty name and items that was not given a name
This is used in sql_yacc.yy to know when to give an item a name.
- select table_name."*' is not anymore same as table_name.*
- removed not used function Item::rename()
- Added comparision of item->name_length before some calls to
my_strcasecmp() to speed up comparison
- Moved Item_sp_variable::make_field() from item.h to item.cc
- Some minimal code changes to avoid copying to const char *
- Fixed wrong error message in wsrep_mysql_parse()
- Fixed wrong code in find_field_in_natural_join() where real_item() was
set when it shouldn't
- ER_ERROR_ON_RENAME was used with extra arguments.
- Removed some (wrong) ER_OUTOFMEMORY, as alloc_root will already
give the error.
TODO:
- Check possible unsafe casts in plugin/auth_examples/qa_auth_interface.c
- Change code to not modify LEX_CSTRING for database name
(as part of lower_case_table_names)
There was no implementation of the virtual method print()
for the Item_window_func class. As a result for a view
containing window function an invalid view definition could
be written in the frm file. When a query that refers to
this view was executed a syntax error was reported.
Make window functions work with an empty over clause by forcing
a sort on the first column of the current join_tab. This is a temporary
fix until we get window functions to work with big tables.
Perform only one table scan for each window function present. We do this
by keeping keeping cursors for each window function frame bound and
running them for each function for every row.
