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.

Added an extra virtual method to the Frame_cursor class to allow cursors
to report the row number to which they are pointing.

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.

The 'IS A' relation is more appropriate for Partition_read_cursor. This
also helps with accessing methods available only to Table_read_cursor.

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.

MDEV-10763: Wrong result - server does not return NULL values from default list partition after ALTER table

Fixed partition pruning for NULL value.

MDEV-10765: Wrong result - query does not retrieve values from default partition on a table partitioned by list columns

Partial matches should be treat as not exact one.

Conflicts:
	sql/mysqld.cc
	sql/slave.cc

When a deadlock kill is detected inside the storage engine, the kill
is not done immediately, to avoid calling back into the storage engine
kill_query method with various lock subsystem mutexes held. Instead the
kill is queued and done later by a slave background thread.

This patch in preparation for fixing TokuDB optimistic parallel
replication, as well as for removing locking hacks in InnoDB/XtraDB in
10.2.

Signed-off-by: Kristian Nielsen <knielsen at knielsen-hq.org>

DEFAULT partition support added to LIST and LIST COLUMN partitioning.
Partitions Prunning added for DEFAULT partititon.

Make the new (CTE-related) code in set_explain_type to take into
account that some JOIN_TABs are non-merged semi-joins, and do not
have a TABLE object.

MDEV-10758 engines/funcs.db_alter_collate_ascii and engines/funcs.db_alter_collate_utf8 fail with wrong results

Add a testcase

Add the testcase

This is the final patch removing some old remainders that are
not needed anymore.

(Other clean-ups were done in earlier commits)

does not work in non-debug modes.

The bug manifested itself for recursive definitions that
used anchors over tables with blobs.

without preceding sys_vars.wsrep_provider_basic

        mysql_prepare_create_table fixed so it doesn't let duplicating
        constraint names. Syntax for CONSTRAINT IF NOT EXISTS added
        and handled in mysql_alter_table.

Based on the patch from Daniil Medvedev (a Google Summer of Code task)

This bug in st_select_lex_node::move_node could result
in invalid select lists in recursive units that could
cause falling into infinite loops when iterating over
selects in such units.

take into account that the list of equal items in
an Item_equal object may contain items with type() == REF_ITEM.