MDEV-7728 - Improve xid cache scalability by using lock-free hash

XID cache is now based on lock-free hash.
Also fixed lf_hash_destroy() to call alloc destructor.

Note that previous implementation had race condition when thread was accessing
XA owned by different thread. This new implementation doesn't fix it either.

1 files changed, 19 insertions, 8 deletions

diff --git a/sql/transaction.cc b/sql/transaction.cc
index 22e3ad7f87c..d6ef160206b 100644
--- a/sql/transaction.cc
+++ b/sql/transaction.cc
@@ -738,7 +738,7 @@ bool trans_xa_start(THD *thd)
     thd->transaction.xid_state.xa_state= XA_ACTIVE;
     thd->transaction.xid_state.rm_error= 0;
     thd->transaction.xid_state.xid.set(thd->lex->xid);
-    if (xid_cache_insert(&thd->transaction.xid_state))
+    if (xid_cache_insert(thd, &thd->transaction.xid_state))
     {
       thd->transaction.xid_state.xa_state= XA_NOTR;
       thd->transaction.xid_state.xid.null();
@@ -801,7 +801,7 @@ bool trans_xa_prepare(THD *thd)
     my_error(ER_XAER_NOTA, MYF(0));
   else if (ha_prepare(thd))
   {
-    xid_cache_delete(&thd->transaction.xid_state);
+    xid_cache_delete(thd, &thd->transaction.xid_state);
     thd->transaction.xid_state.xa_state= XA_NOTR;
     my_error(ER_XA_RBROLLBACK, MYF(0));
   }
@@ -830,6 +830,11 @@ bool trans_xa_commit(THD *thd)
 
   if (!thd->transaction.xid_state.xid.eq(thd->lex->xid))
   {
+    if (thd->fix_xid_hash_pins())
+    {
+      my_error(ER_OUT_OF_RESOURCES, MYF(0));
+      DBUG_RETURN(TRUE);
+    }
     /*
       xid_state.in_thd is always true beside of xa recovery procedure.
       Note, that there is no race condition here between xid_cache_search
@@ -840,7 +845,7 @@ bool trans_xa_commit(THD *thd)
       xa_cache_insert(XID, xa_states), which is called before starting
       client connections, and thus is always single-threaded.
     */
-    XID_STATE *xs= xid_cache_search(thd->lex->xid);
+    XID_STATE *xs= xid_cache_search(thd, thd->lex->xid);
     res= !xs || xs->in_thd;
     if (res)
       my_error(ER_XAER_NOTA, MYF(0));
@@ -848,7 +853,7 @@ bool trans_xa_commit(THD *thd)
     {
       res= xa_trans_rolled_back(xs);
       ha_commit_or_rollback_by_xid(thd->lex->xid, !res);
-      xid_cache_delete(xs);
+      xid_cache_delete(thd, xs);
     }
     DBUG_RETURN(res);
   }
@@ -911,7 +916,7 @@ bool trans_xa_commit(THD *thd)
   thd->server_status&=
     ~(SERVER_STATUS_IN_TRANS | SERVER_STATUS_IN_TRANS_READONLY);
   DBUG_PRINT("info", ("clearing SERVER_STATUS_IN_TRANS"));
-  xid_cache_delete(&thd->transaction.xid_state);
+  xid_cache_delete(thd, &thd->transaction.xid_state);
   thd->transaction.xid_state.xa_state= XA_NOTR;
 
   DBUG_RETURN(res);
@@ -935,14 +940,20 @@ bool trans_xa_rollback(THD *thd)
 
   if (!thd->transaction.xid_state.xid.eq(thd->lex->xid))
   {
-    XID_STATE *xs= xid_cache_search(thd->lex->xid);
+    if (thd->fix_xid_hash_pins())
+    {
+      my_error(ER_OUT_OF_RESOURCES, MYF(0));
+      DBUG_RETURN(TRUE);
+    }
+
+    XID_STATE *xs= xid_cache_search(thd, thd->lex->xid);
     if (!xs || xs->in_thd)
       my_error(ER_XAER_NOTA, MYF(0));
     else
     {
       xa_trans_rolled_back(xs);
       ha_commit_or_rollback_by_xid(thd->lex->xid, 0);
-      xid_cache_delete(xs);
+      xid_cache_delete(thd, xs);
     }
     DBUG_RETURN(thd->get_stmt_da()->is_error());
   }
@@ -961,7 +972,7 @@ bool trans_xa_rollback(THD *thd)
   thd->server_status&=
     ~(SERVER_STATUS_IN_TRANS | SERVER_STATUS_IN_TRANS_READONLY);
   DBUG_PRINT("info", ("clearing SERVER_STATUS_IN_TRANS"));
-  xid_cache_delete(&thd->transaction.xid_state);
+  xid_cache_delete(thd, &thd->transaction.xid_state);
   thd->transaction.xid_state.xa_state= XA_NOTR;
 
   DBUG_RETURN(res);