multi-update was setting up read_set/vcol_set in
multi_update::initialize_tables() that is invoked after
the optimizer (JOIN::optimize_inner()). But some rows - if they're from
const tables - will be read already in the optimizer, and these rows
will not have all necessary column/vcol values.
* multi_update::initialize_tables() uses results from the optimizer
and cannot be moved to be called earlier.
* multi_update::prepare() is called before the optimizer, but
it cannot set up read_set/vcol_set, because the optimizer
might reset them (see SELECT_LEX::update_used_tables()).
As a fix I've added a new method, select_result::prepare_to_read_rows(),
it's called from inside the optimizer just before make_join_statistics().
This fixes a bug where handler::read_range_first (for example)
needed to compare vcol values that were not calculated yet.
As a bonus it fixes few cases where vcols were calculated twice
The idea of this fix was taken from the patch by Roy Lyseng
for mysql-5.6 bug iBug#14740889: "Wrong result for aggregate
functions when executing query through cursor".
Here's Roy's comment for his patch:
"
The problem was that a grouped query did not behave properly when
executed using a cursor. On further inspection, the query used one
intermediate temporary table for the grouping.
Then, Select_materialize::send_result_set_metadata created a temporary
table for storing the query result. Notice that get_unit_column_types()
is used to retrieve column meta-data for the query. The items contained
in this list are later modified so that their result_field points to
the row buffer of the materialized temporary table for the cursor.
But prior to this, these result_field objects have been prepared for
use in the grouping operation, by JOIN::make_tmp_tables_info(), hence
the grouping operation operates on wrong column buffers.
The problem is solved by using the list JOIN::fields when copying data
to the materialized table. This list is set by JOIN::make_tmp_tables_info()
and points to the columns of the last intermediate temporary table of
the executed query. For a UNION, it points to the temporary table
that is the result of the UNION query.
Notice that we have to assign a value to ::fields early in JOIN::optimize()
in case the optimization shortcuts due to a const plan detection.
A more optimal solution might be to avoid creating the final temporary
table when the query result is already stored in a temporary table.
"
The patch does not contain a test case, but the description of the
problem corresponds exactly what could be observed in the test
case for mdev-11081.
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.
Fix window function expressions such as win_func() <operator> expr.
The problem was found in 2 places.
First, when we have complex expressions containing window functions, we
can only compute their final value _after_ we have computed the window
function's values. These values must be stored within the temporary
table that we are using, before sending them off.
This is done by performing an extra copy_funcs call before the final
end_send() call.
Second, such expressions need to have their inner arguments,
changed such that the references within those arguments point to fields within
the temporary table.
Ex: sum(t.a) over (order by t.b) + sum(t.a) over (order by t.b)
Before this fix, t.a pointed to the original table's a field. In order
to compute the sum function's value correctly, it needs to point to the
copy of this field inside the temp table.
This is done by calling split_sum_func for each argument in the
expression in turn.
The win.test results have also been updated as they contained wrong
values for such a use case.
The condition pushed into WHERE/HAVING of a materialized
view/derived table may differ for different executions of
the same prepared statement. That's why the should be
ANDed with the existing WHERE/HAVING conditions only after all
permanent transformations of these conditions has been
performed.
- Tabular EXPLAIN now prints "RECURSIVE UNION".
- There is a basic implementation of EXPLAIN FORMAT=JSON.
- it produces "recursive_union" JSON struct
- No other details or ANALYZE support, yet.
explain for the query containing WITH clause
with an unreferenced CTE caused a crash.
Added a test covered this case.
Also added a test for usage CTE in different parts of union.
Temporary tables created for recursive CTE
were instantiated at the prepare phase. As
a result these temporary tables missed
indexes for look-ups and optimizer could not
use them.
MDEV-10134 Add full support for DEFAULT
- Added support for using tables with MySQL 5.7 virtual fields,
including MySQL 5.7 syntax
- Better error messages also for old cases
- CREATE ... SELECT now also updates timestamp columns
- Blob can now have default values
- Added new system variable "check_constraint_checks", to turn of
CHECK constraint checking if needed.
- Removed some engine independent tests in suite vcol to only test myisam
- Moved some tests from 'include' to 't'. Should some day be done for all tests.
- FRM version increased to 11 if one uses virtual fields or constraints
- Changed to use a bitmap to check if a field has got a value, instead of
setting HAS_EXPLICIT_VALUE bit in field flags
- Expressions can now be up to 65K in total
- Ensure we are not refering to uninitialized fields when handling virtual fields or defaults
- Changed check_vcol_func_processor() to return a bitmap of used types
- Had to change some functions that calculated cached value in fix_fields to do
this in val() or getdate() instead.
- store_now_in_TIME() now takes a THD argument
- fill_record() now updates default values
- Add a lookahead for NOT NULL, to be able to handle DEFAULT 1+1 NOT NULL
- Automatically generate a name for constraints that doesn't have a name
- Added support for ALTER TABLE DROP CONSTRAINT
- Ensure that partition functions register virtual fields used. This fixes
some bugs when using virtual fields in a partitioning function
Actually mutually recursive CTE were not functional. Now the code
for mutually recursive CTE looks like functional, but still needs
re-writing.
Added many new test cases for mutually recursive CTE.
Post-fix #2:
- Update test results
- Make the optimization conditional under @@optimizer_switch flag.
- The optimization is now disabled by default, so .result files
are changed back to be what they were before the MDEV-8989 patch.
Added test cases to check the fix.
Fixed the problem of wrong types of recursive tables when the type of anchor part does not coincide with the
type of recursive part.
Prevented usage of marerialization and subquery cache for subqueries with recursive references.
Introduced system variables 'max_recursion_level'.
Added a test case to test usage of this variable.
Variant #4 of the fix.
Make ORDER BY optimization functions take into account multiple
equalities. This is done in several places:
- remove_const() checks whether we can sort the first table in the
join, or we need to put rows into temp.table and then sort.
- test_if_order_by_key() checks whether there are indexes that
can be used to produce the required ordering
- make_unireg_sortorder() constructs sort criteria for filesort.
Added the check whether there are set functions in the specifications of recursive CTE.
Added the check whether there are recursive references in subqueries.
Introduced boolean system variable 'standards_compliant_cte'. By default it's set to 'on'.
When it's set to 'off' non-standard compliant CTE can be executed.
When simplify_joins() converts an outer join to an inner, it should
reset the value of TABLE::dep_tables. This is needed, because the
function may have already set TABLE::dep_tables according to the outer
join dependency.
This change refactors the "table_expression" rule in sql_yacc.yy.
Queries with subselects and derived tables, as well as "CREATE TABLE ... SELECT"
now return syntax error instead of "Incorrect usage of PROCEDURE and ...".
