MDEV-20950 Reduce size of record offsetsbb-10.2-MDEV-20950-stack-offsets

offset_t: this is a type which represents one record offset.
It's unsigned short int.

a lot of functions: replace ulint with offset_t

btr_pcur_restore_position_func(),
page_validate(),
row_ins_scan_sec_index_for_duplicate(),
row_upd_clust_rec_by_insert_inherit_func(),
row_vers_impl_x_locked_low(),
trx_undo_prev_version_build():
  allocate record offsets on the stack instead of waiting for rec_get_offsets()
  to allocate it from mem_heap_t. So, reducing  memory allocations.

RECORD_OFFSET, INDEX_OFFSET:
  now it's less convenient to store pointers in offset_t*
  array. One pointer occupies now several offset_t. And those constant are start
  indexes into array to places where to store pointer values

REC_OFFS_HEADER_SIZE: adjusted for the new reality

REC_OFFS_NORMAL_SIZE:
  increase size from 100 to 300 which means less heap allocations.
  And sizeof(offset_t[REC_OFFS_NORMAL_SIZE]) now is 600 bytes which
  is smaller than previous 800 bytes.

REC_OFFS_SEC_INDEX_SIZE: adjusted for the new reality

rem0rec.h, rem0rec.ic, rem0rec.cc:
  various arguments, return values and local variables types were changed to
  fix numerous integer conversions issues.

enum field_type_t:
  offset types concept was introduces which replaces old offset flags stuff.
  Like in earlier version, 2 upper bits are used to store offset type.
  And this enum represents those types.

REC_OFFS_SQL_NULL, REC_OFFS_MASK: removed

get_type(), set_type(), get_value(), combine():
  these are convenience functions to work with offsets and it's types

rec_offs_base()[0]:
  still uses an old scheme with flags REC_OFFS_COMPACT and REC_OFFS_EXTERNAL

rec_offs_base()[i]:
  these have type offset_t now. Two upper bits contains type.

1 files changed, 2 insertions, 2 deletions

diff --git a/storage/innobase/row/row0undo.cc b/storage/innobase/row/row0undo.cc
index 7a245f8279c..109bf1004ca 100644
--- a/storage/innobase/row/row0undo.cc
+++ b/storage/innobase/row/row0undo.cc
@@ -167,8 +167,8 @@ row_undo_search_clust_to_pcur(
 	row_ext_t**	ext;
 	const rec_t*	rec;
 	mem_heap_t*	heap		= NULL;
-	ulint		offsets_[REC_OFFS_NORMAL_SIZE];
-	ulint*		offsets		= offsets_;
+	offset_t	offsets_[REC_OFFS_NORMAL_SIZE];
+	offset_t*	offsets		= offsets_;
 	rec_offs_init(offsets_);
 
 	ut_ad(!node->table->skip_alter_undo);