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From:magnus.blaudd Date:April 25 2012 12:36pm
Subject:bzr push into mysql-trunk branch (magnus.blaudd:3735 to 3736) WL#5906
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 3736 magnus.blaudd@stripped	2012-04-25
      WL#5906 read before write removal (RBWR)
       - Adapt patch to latest trunk.
       - Since both update and delete now does all the checks in one
         place, the common code has been factored out into TABLE::check_read_removal() which is then
        called both from mysql_update() and mysql_delete() 
       - Remove handler::read_before_write_removal_supported() in favor of using
        the HA_READ_BEFORE_WRITE_REMOVAL table flag.
       - Rename handler::read_before_write_removal_rows_written() to handler::end_read_removal()
       - Rename handler::read_before_write_removal_possible() to handler::start_read_removal()
       - Remove unnecessary DBUG printouts

    modified:
      sql/ha_ndbcluster.cc
      sql/ha_ndbcluster.h
      sql/handler.h
      sql/sql_delete.cc
      sql/sql_update.cc
      sql/table.cc
      sql/table.h
 3735 magnus.blaudd@stripped	2012-04-25 [merge]
      Merge trunk-wl5906 with trunk

    modified:
      sql/handler.h
      sql/sql_delete.cc
      sql/sql_update.cc
=== modified file 'sql/ha_ndbcluster.cc'
--- a/sql/ha_ndbcluster.cc	2012-03-28 11:25:37 +0000
+++ b/sql/ha_ndbcluster.cc	2012-04-25 12:30:33 +0000
@@ -7138,10 +7138,10 @@ int ha_ndbcluster::extra(enum ha_extra_f
 }
 
 
-bool ha_ndbcluster::read_before_write_removal_possible()
+bool ha_ndbcluster::start_read_removal()
 {
   THD *thd= table->in_use;
-  DBUG_ENTER("read_before_write_removal_possible");
+  DBUG_ENTER("start_read_removal");
 
   if (uses_blob_value(table->write_set))
   {
@@ -7188,9 +7188,10 @@ bool ha_ndbcluster::read_before_write_re
 }
 
 
-ha_rows ha_ndbcluster::read_before_write_removal_rows_written(void) const
+ha_rows ha_ndbcluster::end_read_removal(void)
 {
-  DBUG_ENTER("read_before_write_removal_rows_written");
+  DBUG_ENTER("end_read_removal");
+  DBUG_ASSERT(m_read_before_write_removal_possible);
   DBUG_PRINT("info", ("updated: %llu, deleted: %llu",
                       m_rows_updated, m_rows_deleted));
   DBUG_RETURN(m_rows_updated + m_rows_deleted);

=== modified file 'sql/ha_ndbcluster.h'
--- a/sql/ha_ndbcluster.h	2012-03-28 11:25:37 +0000
+++ b/sql/ha_ndbcluster.h	2012-04-25 12:30:33 +0000
@@ -305,9 +305,8 @@ class ha_ndbcluster: public handler
 #endif
   void get_dynamic_partition_info(PARTITION_STATS *stat_info, uint part_id);
   uint32 calculate_key_hash_value(Field **field_array);
-  bool read_before_write_removal_supported() const { return true; }
-  bool read_before_write_removal_possible();
-  ha_rows read_before_write_removal_rows_written(void) const;
+  bool start_read_removal(void);
+  ha_rows end_read_removal(void);
   int extra(enum ha_extra_function operation);
   int extra_opt(enum ha_extra_function operation, ulong cache_size);
   int reset();

=== modified file 'sql/handler.h'
--- a/sql/handler.h	2012-04-25 07:05:16 +0000
+++ b/sql/handler.h	2012-04-25 12:30:33 +0000
@@ -2169,27 +2169,23 @@ public:
   virtual int extra_opt(enum ha_extra_function operation, ulong cache_size)
   { return extra(operation); }
 
-  /**
-    Informs handler that it is possible to optimize away the real read
-    operation from the handler for the current table and instead
-    use a generated read to optimze simple UPDATEs and DELETEs.
-
-    @return true if handler supports rbwr for this write
+  /*
+    Start read (before write) removal on the current table. Fake rows may
+    be returned while reading from the selected index. This is used to
+    optimise simple UPDATE and DELETEs.The handler may refuse to start
+    due to internal limitations in the storage engine. Successful start
+    is always followed by end.
+    Function will only be called for handles who returns
+    HA_READ_BEFORE_WRITE_REMOVAL from table_flags()
   */
-  virtual bool read_before_write_removal_possible(void)
-  { return false; }
+  virtual bool start_read_removal(void)
+  { DBUG_ASSERT(0); return false; }
 
-  /**
-    Return the number of rows the handler has written while using
-    read before write removal
-
-    @return the number of rows actually written
-   */
-  virtual ha_rows read_before_write_removal_rows_written(void) const
-  {
-    DBUG_ASSERT(false);
-    return (ha_rows) 0;
-  }
+  /*
+    End read (before write) removal and return the number of rows really written
+  */
+  virtual ha_rows end_read_removal(void)
+  { DBUG_ASSERT(0); return (ha_rows) 0; }
 
   /**
     In an UPDATE or DELETE, if the row under the cursor was locked by another

=== modified file 'sql/sql_delete.cc'
--- a/sql/sql_delete.cc	2012-04-25 07:05:16 +0000
+++ b/sql/sql_delete.cc	2012-04-25 12:30:33 +0000
@@ -343,35 +343,13 @@ bool mysql_delete(THD *thd, TABLE_LIST *
   else
     will_batch= !table->file->start_bulk_delete();
 
-  /*
-    Read removal is possible if the selected quick read
-    method is using full unique index
-  */
-  if (table->file->ha_table_flags() & HA_READ_BEFORE_WRITE_REMOVAL &&
-      select && select->quick &&
-      will_batch &&
-      !thd->lex->ignore &&
-      !using_limit)
-  {
-    const uint idx = select->quick->index;
-    DBUG_PRINT("rbwr", ("checking index: %d", idx));
-    const KEY *key= table->key_info + idx;
-    if (key->flags & HA_NOSAME)
-    {
-      DBUG_PRINT("rbwr", ("index is unique"));
-      bitmap_clear_all(&table->tmp_set);
-      table->mark_columns_used_by_index_no_reset(idx, &table->tmp_set);
-      if (bitmap_cmp(&table->tmp_set, table->read_set))
-      {
-        DBUG_PRINT("rbwr", ("using whole index, rbwr possible"));
-        read_removal=
-          table->file->read_before_write_removal_possible();
-      }
-    }
-  }
-
   table->mark_columns_needed_for_delete();
 
+  if ((table->file->ha_table_flags() & HA_READ_BEFORE_WRITE_REMOVAL) &&
+      !using_limit &&
+      select && select->quick && select->quick->index != MAX_KEY)
+    read_removal= table->check_read_removal(select->quick->index);
+
   while (!(error=info.read_record(&info)) && !thd->killed &&
 	 ! thd->is_error())
   {
@@ -434,9 +412,7 @@ bool mysql_delete(THD *thd, TABLE_LIST *
   if (read_removal)
   {
     /* Only handler knows how many records were really written */
-    DBUG_PRINT("rbwr", ("old deleted: %ld", (long)deleted));
-    deleted= table->file->read_before_write_removal_rows_written();
-    DBUG_PRINT("rbwr", ("really deleted: %ld", (long)deleted));
+    deleted= table->file->end_read_removal();
   }
   THD_STAGE_INFO(thd, stage_end);
   end_read_record(&info);

=== modified file 'sql/sql_update.cc'
--- a/sql/sql_update.cc	2012-04-25 07:05:16 +0000
+++ b/sql/sql_update.cc	2012-04-25 12:30:33 +0000
@@ -474,35 +474,6 @@ int mysql_update(THD *thd,
     }
   } // Ends scope for optimizer trace wrapper
 
-  /*
-    Read removal is possible if the selected quick read
-    method is using full unique index
-
-    NOTE! table->read_set currently holds the columns which are
-    used for the WHERE clause(this info is most likely already
-    available in select->quick, but where?)
-  */
-  if (table->file->ha_table_flags() & HA_READ_BEFORE_WRITE_REMOVAL &&
-      select && select->quick && select->quick->index != MAX_KEY &&
-      !ignore &&
-      !using_limit)
-  {
-    const uint idx= select->quick->index;
-    DBUG_PRINT("rbwr", ("checking index: %d", idx));
-    const KEY *key= table->key_info + idx;
-    if (key->flags & HA_NOSAME)
-    {
-      DBUG_PRINT("rbwr", ("index is unique"));
-      bitmap_clear_all(&table->tmp_set);
-      table->mark_columns_used_by_index_no_reset(idx, &table->tmp_set);
-      if (bitmap_cmp(&table->tmp_set, table->read_set))
-      {
-        DBUG_PRINT("rbwr", ("using full index, rbwr possible"));
-        read_removal= true;
-      }
-    }
-  }
-
   /* If running in safe sql mode, don't allow updates without keys */
   if (table->quick_keys.is_clear_all())
   {
@@ -688,10 +659,6 @@ int mysql_update(THD *thd,
     }
     if (used_index < MAX_KEY && old_covering_keys.is_set(used_index))
       table->set_keyread(false);
-
-    /* Rows are already read -> not possible to remove */
-    DBUG_PRINT("rbwr", ("rows are already read, turning off rbwr"));
-    read_removal= false;
   }
 
   if (ignore)
@@ -730,13 +697,11 @@ int mysql_update(THD *thd,
   else
     will_batch= !table->file->start_bulk_update();
 
-  if (read_removal &&
-      will_batch &&
+  if ((table->file->ha_table_flags() & HA_READ_BEFORE_WRITE_REMOVAL) &&
+      !ignore && !using_limit &&
+      select && select->quick && select->quick->index != MAX_KEY &&
       check_constant_expressions(values))
-  {
-    DBUG_ASSERT(select && select->quick);
-    read_removal= table->file->read_before_write_removal_possible();
-  }
+    read_removal= table->check_read_removal(select->quick->index);
 
   // For prepare_record_for_error_message():
   if (table->file->ha_table_flags() & HA_PARTIAL_COLUMN_READ)
@@ -952,15 +917,9 @@ int mysql_update(THD *thd,
   if (read_removal)
   {
     /* Only handler knows how many records really was written */
-    DBUG_PRINT("rbwr", ("adjusting updated: %ld, found: %ld",
-                        (long)updated, (long)found));
-
-    updated= table->file->read_before_write_removal_rows_written();
+    updated= table->file->end_read_removal();
     if (!records_are_comparable(table))
       found= updated;
-
-    DBUG_PRINT("rbwr", ("really updated: %ld, found: %ld",
-                        (long)updated, (long)found));
   }
 
   if (!transactional_table && updated > 0)

=== modified file 'sql/table.cc'
--- a/sql/table.cc	2012-04-18 13:06:39 +0000
+++ b/sql/table.cc	2012-04-25 12:30:33 +0000
@@ -5997,6 +5997,37 @@ Field *TABLE::get_timestamp_field()
 }
 
 
+/*
+  Read removal is possible if the selected quick read
+  method is using full unique index
+
+  @param index              Number of the index used for read
+
+  @retval true   success, read removal started
+  @retval false  read removal not started
+*/
+
+bool TABLE::check_read_removal(uint index)
+{
+  DBUG_ENTER("check_read_removal");
+  DBUG_ASSERT(file->ha_table_flags() & HA_READ_BEFORE_WRITE_REMOVAL);
+  DBUG_ASSERT(index != MAX_KEY);
+
+  // Index must be unique
+  if ((key_info[index].flags & HA_NOSAME) == 0)
+    DBUG_RETURN(false);
+
+  // Full index must be used
+  bitmap_clear_all(&tmp_set);
+  mark_columns_used_by_index_no_reset(index, &tmp_set);
+  if (!bitmap_cmp(&tmp_set, read_set))
+    DBUG_RETURN(false);
+
+  // Start read removal in handler
+  DBUG_RETURN(file->start_read_removal());
+}
+
+
 /**
   Test if the order list consists of simple field expressions
 

=== modified file 'sql/table.h'
--- a/sql/table.h	2012-04-16 09:26:56 +0000
+++ b/sql/table.h	2012-04-25 12:30:33 +0000
@@ -1157,6 +1157,8 @@ public:
   Field *get_timestamp_field();
 
   bool update_const_key_parts(Item *conds);
+
+  bool check_read_removal(uint index);
 };
 
 

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bzr push into mysql-trunk branch (magnus.blaudd:3735 to 3736) WL#5906magnus.blaudd25 Apr