Fix for BUG#39697 "Maria: hang when failing to insert due to UNIQUE (seen in pushbuild2 too)"

It was a forgotten rw_unlock(), due to the deadlock detector feature (so bug was only in 5.1-maria, not
6.0-maria).

mysql-test/suite/maria/r/maria3.result:
  result, all fine
mysql-test/suite/maria/t/maria3.test:
  Test of BUG#39697: two scenarios (transactional tables, and non-transactional table but dynamic row format so still taking the rwlock) where the hang happened.
  t2 added by this test was masked by a temporary table created earlier in the test, which we forgot to drop.
storage/maria/ha_maria.cc:
  use new macro
storage/maria/ma_blockrec.c:
  use new macro
storage/maria/ma_commit.c:
  use new macro
storage/maria/ma_init.c:
  putting address of dummy_transaction_object in --debug trace can be useful
storage/maria/ma_open.c:
  use new macro
storage/maria/ma_write.c:
  if local_lock_tree is true, we have acquired keyinfo->root_lock so need to release it before "goto err".
  A pair of assertions so that our usage of TrIDs is kept sensible.
storage/maria/maria_def.h:
  A macro so that changes of MARIA_HA::trn can be tracked with --debug. It helped to understand in what cases,
  in maria_write(), we could have !(info->dup_key_trid == info->trn->trid) && !share->now_transactional
  (answer: ALTER TABLE adding UNIQUE index on transactional table).

1 files changed, 13 insertions, 0 deletions

diff --git a/storage/maria/maria_def.h b/storage/maria/maria_def.h
index 42a78261d20..0ab7c86b594 100644
--- a/storage/maria/maria_def.h
+++ b/storage/maria/maria_def.h
@@ -698,6 +698,19 @@ struct st_maria_handler
 #define get_pack_length(length) ((length) >= 255 ? 3 : 1)
 #define _ma_have_versioning(info) ((info)->row_flag & ROW_FLAG_TRANSID)
 
+/**
+   Sets table's trn and prints debug information
+   @param tbl              MARIA_HA of table
+   @param newtrn           what to put into tbl->trn
+   @note cast of newtrn is because %p of NULL gives warning (NULL is int)
+*/
+#define _ma_set_trn_for_table(tbl, newtrn) do {                         \
+    DBUG_PRINT("info",("table: %p trn: %p -> %p",                       \
+                       (tbl), (tbl)->trn, (void *)(newtrn)));           \
+    (tbl)->trn= (newtrn);                                               \
+  } while (0)
+
+
 #define MARIA_MIN_BLOCK_LENGTH	20		/* Because of delete-link */
 /* Don't use to small record-blocks */
 #define MARIA_EXTEND_BLOCK_LENGTH	20