Statements affected by this bug have all the following
1) select statements with a sub-query
2) that sub-query includes a group-by clause
3) that group-by clause contains an expression
4) that expression has a reference to view
When a view is used in a group by expression, and that group by can be
eliminated in a sub-query simplification as part of and outer condition
that could be in, exists, > or <, then the table structure left behind
will have a unit that contains a null select_lex pointer.
If this happens as part of a prepared statement, or execute in a stored
procedure for the second time, then, when the statement is executed, the table
list entry for that, now eliminated, view is "opened" and "reinit"ialized.
This table entry's unit no longer has a select_lex pointer.
Prior to MDEV-31995 this was of little consequence, but now following this
null pointer will cause a crash.
Reviewed by Igor Babaev (igor@mariadb.com)
MDEV-30668 Set function aggregated in outer select used in view definition
This patch fixes two bugs concerning views whose specifications contain
subqueries with set functions aggregated in outer selects.
Due to the first bug those such views that have implicit grouping were
considered as mergeable. This led to wrong result sets for selects from
these views.
Due to the second bug the aggregation select was determined incorrectly and
this led to bogus error messages.
The patch added several test cases for these two bugs and for four other
duplicate bugs.
The patch also enables view-protocol for many other test cases.
Approved by Oleksandr Byelkin <sanja@mariadb.com>
This bug affected queries with views / derived_tables / CTEs whose
specifications were of the form
(SELECT ... LIMIT <n>) ORDER BY ...
Units representing such specifications contains one SELECT_LEX structure
for (SELECT ... LIMIT <n>) and additionally SELECT_LEX structure for
fake_select_lex. This fact should have been taken into account in the
function mysql_derived_fill().
This patch has to be applied to 10.2 and 10.3 only.
If a derived table has SELECT DISTINCT, provide index statistics for it so that the join optimizer in the
upper select knows that ref access to the table will produce one row.
This bug happened for queries that used a materialized view that
renamed columns of the specifying query in an inner table of
an outer join. For such a query name resolution for a column
belonging the view could fail if the underlying column was
non-nullable.
When creating the defintion of the the temporary table for
the materialized view used in the inner part of an outer join
the definition of the non-nullable columns are created by the
function create_tmp_field_from_item() that names the columns
according to the names of the underlying columns. So these names
should be changed for the view column names.
This bug cannot be reproduced in 10.2 because there setup_fields()
called when preparing joins in the view specification effectively
renames the underlying columns in the function find_field_in_view().
In 10.3 this renaming was removed as improper
(see Monty's commit b478276b04).