- 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
It allows to push conditions into derived with window functions not
only in the cases when the window specifications of these window
functions use the same partition, but also in the cases when the window
functions use partitions that share only some fields. In these
cases only the conditions over the common fields are pushed.
The usage of windows functions when all tables were optimized away
by min/max optimization were not supported. As result a result,
the queries that used window functions with min/max aggregation
over the whole table returned wrong result sets.
The patch fixed this problem.
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)
The bug was not visible in current HEAD. Introduced test case to catch
regressions. Also improve error messages regarding distinct usage in
window functions.
The bug was caused by several issues.
2 problems in seek_io_cache. Due to wrong offsets used, we would end up
seeking way too much (first change), or over the intended seek point
(second change). Fixing it requires correctly detecting available data
in buffer (first change), and not using "IO_SIZE alligned" reads. The
second is needed because _my_b_cache_read adjusts the pos_in_file itself
based on read_pos and read_end. Pretending buffer is empty when we want
to force a read will aleviate this problem.
Secondly, the big-table cursors didn't repect the interface definitions
of always returning the rownumber that Table_read_cursor::fetch() would activate.
At the same time, next(), prev() and move_to() should not perform any
row activation.
Window functions need to be computed after applying the HAVING clause.
An optimization that we have for regular, non-window function, cases is
to apply having only during sending of the rows to the client. This
allows rows that should be filtered from the temporary table used to
store aggregation results to be stored there.
This behaviour is undesireable for window functions, as we have to
compute window functions on the result-set after HAVING is applied.
Storing extra rows in the table leads to wrong values as the frame
bounds might capture those -to be filtered afterwards- rows.
The same approach is needed for LAST_VALUE, otherwise the LAST_VALUE sum
functions are not cleared correctly. Now LAST_VALUE behaves as NTH_VALUE
with 0 offset, only that the frame that it is examining is the bottom bound,
not the top bound.
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.
Add support for having multiple IO_CACHEs with type=READ_CACHE to share
the file they are reading from.
Each IO_CACHE keeps its own in-memory buffer. When doing a read or seek
operation on the file, it notifies other IO_CACHEs that the file position
has been changed.
Make Rowid_seq_cursor use cloned IO_CACHE when reading filesort result.
Refactour out (into a copy for now) the logic of Item_sum_hybrid, to
allow for multiple arguments. It does not contain the comparator
members. The result is the class Item_sum_hybrid_simple.
LEAD and LAG make use of this Item to store previous rows in a chache.
It also helps in specifying the field type. Currently LEAD/LAG do not
support default values.
NTH_VALUE behaves identical to LEAD and LAG, except that the starting
position cursor is placed on the top of the frame instead of the current
row.
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.
The positional cursor now fetches rows based on the positional
cursor and an offset (if present). It will fetch rows, based on the
offset, only if the required position is not out of bounds.
With clever use of partition bounds, we only need to add one row to the
items at a time. This way we remove the need to "reset" the item and run
through the full partition again.
We can set values in the record buffer first and only perform one table
write call at the end. No need to write to file every time one column is
updated.
Also, remove unused method from Table_read_cursor.
This makes them behave exactly like CURRENT ROW. Standard specifies
unsigned integer, which includes the value 0.
Expand the win_min_max test to include this kind of frame definitions.
Cursors now report their current row number as the boundary of the
partition. This is used by Frame_scan_cursor to compute aggregate
functions that do not support removal.
Currently cursors automatically add values to the sum functions they
manage. There are use cases when we just want to figure out the frame
boundaries, without actually adding/removing values from them.
When specifying a RANGE type frame that exceeds the partition size, both
for the top and bottom cursors we end up removing more rows than added
to the aggregate function. This happens because our TOP range cursor,
which removes values from the aggregate function, would be allowed to breach
partition boundaries, while the BOTTOM range cursor would not.
To prevent this from happening, force the TOP range cursor to only move
within the current partition, as does the BOTTOM range cursor.
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.
- Avoid some realloc() during startup
- Ensure that file_key_management_plugin frees it's memory early, even if
it's linked statically.
- Fixed compiler warnings from unused variables and missing destructors
- Fixed wrong indentation
Make Frame_range_current_row_bottom to take into account partition bounds.
Other partition bounds that could potentially hit the end of partition are
Frame_range_n_bottom, Frame_n_rows_following, Frame_unbounded_following,
and they all had end-of-partition protection.
To simplify the code, factored out end-of-partition checks into
class Partition_read_cursor.
This bug revealed a serious problem: if the same partition list
was used in two window specifications then the temporary table created
to calculate window functions contained fields for two identical
partitions. This problem was fixed as well.
n=0 in "ROWS 0 PRECEDING" is valid, add handling for it:
- Adjust the assert
- Bottom bound of 'ROW 0 PRECEDING' is actually looking at the current
row, that is, it needs to process partition's first row directly in
Frame_n_rows_preceding::next_partition().
- Added testcases
" The sort order for the sub-sequence of window functions starting
from the element marked by SORTORDER_CHANGE_FLAG up to the next
element marked by SORTORDER_CHANGE_FLAG must be taken from the
last element of the sub-sequence (not from the first one)."
- Rename Window_funcs_computation to Window_funcs_computation_step
- Introduce Window_func_sort which invokes filesort and then
invokes computation of all window functions that use this ordering.
- Expose Window functions' sort operations in EXPLAIN|ANALYZE FORMAT=JSON
that the call-back comparison function returns a positive
number when arg1 < arg2, and a negative number when arg1 > arg2.
This is not in line with other implementation of sorting
algorithm.
Changed bubble_sort: now a negative result from the comparison
function means that arg1 < arg2, and positive result means
that arg1 > arg2.
Changed accordingly all call-back functions that are used as
parameters in the call of bubble_sort.
Added a test case to check the proper sorting of window functions.
- Hook window function computation into the right location.
- Add a testcase which shows that HAVING is now checked before
the window function computation step.
We can call setup_partition_border_check() from
JOIN::make_aggr_tables_info(), provided that call is made after
appropriate set_items_ref_array() call.
Added class Window_funcs_computation, with setup() method to setup
execution, and exec() to run window function computation.
setup() is currently trivial. In the future, it is expected to optimize
the number of sorting operations and passes that are done over the temp.
table.
- Make Item_XXX::cleanup() clean List<Cached_item> orderby_fields.
(Items survive across PS re-executions. Cached_item don't, because
they keep pointers to fix_field'ed items, etc)
- Move List<Cached_item> out into Group_bound_tracker.
Item_func_or_sum.
Implemented method update_used_tables for class Item_findow_func.
Added the flag Item::with_window_func.
Made sure that window functions could be used only in SELECT list
and ORDER BY clause.
Added test cases that checked different illegal placements of
window functions.
with window functions. Added the test case for it.
Also allowed to use aliases for set functions in partition and order lists
that are specified in window functions.
of the type SQL_I_List<ORDER> rather then the objects of this type.
It allows to replace easily one instance of such a list for another.
Besides it will facilitate to compare two lists if they originate from the
same window specification.
In fact any direct assignment for objects of the type SQL_I_List<ORDER>
was not valid.
It is based on the sum() function, thus much of the logic is shared.
Considering that there are 2 counters stored within the function, one
that handles the null value, while the other that handles the divisor
for the avg computation, it is possible to remove the counter from the
Item_sum_avg. I have not removed it in this patch as we may choose to
refactor the whole code into a separate class.
This remains to be dicussed.
The counter keeps track of the number of items added to the sum
function. It is increased when we add a value to the sum function and
decreased when it is removed.
Add support for "RANGE n PRECEDING|FOLLOWING" frame bounds.
- n is currently limited to whatever Item and Item_sum_plus/minus
can handle (i.e. no DATETIME intervals).
- Didn't check NULL value handling yet.
Part#2: Fix a couple more issues in rows-type frames.
This also has a code cleanup:
- introduce a separate Frame_rows_current_row_(top,bottom). This is
is a special case which doesn't need its cursor or partition bound check
- Split Frame_n_rows into
= Frame_n_rows_preceding (this one is now much simpler)
= Frame_n_rows_following (simpler and works but may need some work still)
Part#1: Frame_n_rows::next_partition() should not assume that the
current table->record[0] points to the first row in the partition.
Since cursor supports move_to() operation, we dont need this.
Introduce explicitly-defined cursors.
- Rowid_seq_cursor just reads the rowid sequence
- Table_read_cursor also reads rows for the rowids
- Also, we need a kind of cursor that stops at partition boundary?
- Add temporary code: clone_read_record() clones READ_RECORD structure,
as long as it is used for reading filesort() result that fits into
memory.
- Add frame bounds for ROWS-type frames. ROWS n PRECEDING|FOLLOWING,
ROWS UNBOUNDED PRECEDING|FOLLOWING, CURRENT ROW are supported.
- Add Item_sum_count::remove() which allows "streaming" computation
of COUNT() over a moving frame.
