5.5-merge

1 files changed, 196 insertions, 39 deletions

diff --git a/sql/sql_update.cc b/sql/sql_update.cc
index 76c90e40b17..bb4540b48f3 100644
--- a/sql/sql_update.cc
+++ b/sql/sql_update.cc
@@ -1,4 +1,4 @@
-/* Copyright 2000-2008 MySQL AB, 2008-2009 Sun Microsystems, Inc.
+/* Copyright (c) 2000, 2010, Oracle and/or its affiliates. All rights reserved.
 
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -42,11 +42,68 @@
                          // mysql_handle_derived,
                          // mysql_derived_filling
 
-/* Return 0 if row hasn't changed */
 
-bool compare_record(TABLE *table)
+/**
+   True if the table's input and output record buffers are comparable using
+   compare_records(TABLE*).
+ */
+bool records_are_comparable(const TABLE *table) {
+  return ((table->file->ha_table_flags() & HA_PARTIAL_COLUMN_READ) == 0) ||
+    bitmap_is_subset(table->write_set, table->read_set);
+}
+
+
+/**
+   Compares the input and outbut record buffers of the table to see if a row
+   has changed. The algorithm iterates over updated columns and if they are
+   nullable compares NULL bits in the buffer before comparing actual
+   data. Special care must be taken to compare only the relevant NULL bits and
+   mask out all others as they may be undefined. The storage engine will not
+   and should not touch them.
+
+   @param table The table to evaluate.
+
+   @return true if row has changed.
+   @return false otherwise.
+*/
+bool compare_records(const TABLE *table)
 {
+  DBUG_ASSERT(records_are_comparable(table));
+
+  if ((table->file->ha_table_flags() & HA_PARTIAL_COLUMN_READ) != 0)
+  {
+    /*
+      Storage engine may not have read all columns of the record.  Fields
+      (including NULL bits) not in the write_set may not have been read and
+      can therefore not be compared.
+    */ 
+    for (Field **ptr= table->field ; *ptr != NULL; ptr++)
+    {
+      Field *field= *ptr;
+      if (bitmap_is_set(table->write_set, field->field_index))
+      {
+        if (field->real_maybe_null())
+        {
+          uchar null_byte_index= field->null_ptr - table->record[0];
+          
+          if (((table->record[0][null_byte_index]) & field->null_bit) !=
+              ((table->record[1][null_byte_index]) & field->null_bit))
+            return TRUE;
+        }
+        if (field->cmp_binary_offset(table->s->rec_buff_length))
+          return TRUE;
+      }
+    }
+    return FALSE;
+  }
+  
+  /* 
+     The storage engine has read all columns, so it's safe to compare all bits
+     including those not in the write_set. This is cheaper than the field-by-field
+     comparison done above.
+  */ 
   if (table->s->can_cmp_whole_record)
+    // Fixed-size record: do bitwise comparison of the records 
     return cmp_record(table,record[1]);
   /* Compare null bits */
   if (memcmp(table->null_flags,
@@ -204,7 +261,6 @@ int mysql_update(THD *thd,
   bool		using_limit= limit != HA_POS_ERROR;
   bool		safe_update= test(thd->variables.option_bits & OPTION_SAFE_UPDATES);
   bool          used_key_is_modified= FALSE, transactional_table, will_batch;
-  bool		can_compare_record;
   int           res;
   int		error, loc_error;
   uint          used_index, dup_key_found;
@@ -240,11 +296,17 @@ int mysql_update(THD *thd,
   if (lock_tables(thd, table_list, table_count, 0))
     DBUG_RETURN(1);
 
-  if (mysql_handle_derived(thd->lex, &mysql_derived_prepare) ||
-      (thd->fill_derived_tables() &&
-       mysql_handle_derived(thd->lex, &mysql_derived_filling)))
+  if (mysql_handle_derived(thd->lex, &mysql_derived_prepare))
     DBUG_RETURN(1);
 
+  if (thd->fill_derived_tables() &&
+      mysql_handle_derived(thd->lex, &mysql_derived_filling))
+  {
+    mysql_handle_derived(thd->lex, &mysql_derived_cleanup);
+    DBUG_RETURN(1);
+  }
+  mysql_handle_derived(thd->lex, &mysql_derived_cleanup);
+
   thd_proc_info(thd, "init");
   table= table_list->table;
 
@@ -582,15 +644,6 @@ int mysql_update(THD *thd,
   if (table->file->ha_table_flags() & HA_PARTIAL_COLUMN_READ)
     table->prepare_for_position();
 
-  /*
-    We can use compare_record() to optimize away updates if
-    the table handler is returning all columns OR if
-    if all updated columns are read
-  */
-  can_compare_record= (!(table->file->ha_table_flags() &
-                         HA_PARTIAL_COLUMN_READ) ||
-                       bitmap_is_subset(table->write_set, table->read_set));
-
   while (!(error=info.read_record(&info)) && !thd->killed)
   {
     update_virtual_fields(thd, table);
@@ -608,7 +661,7 @@ int mysql_update(THD *thd,
 
       found++;
 
-      if (!can_compare_record || compare_record(table))
+      if (!records_are_comparable(table) || compare_records(table))
       {
         if ((res= table_list->view_check_option(thd, ignore)) !=
             VIEW_CHECK_OK)
@@ -948,6 +1001,108 @@ static table_map get_table_map(List<Item> *items)
   return map;
 }
 
+/**
+  If one row is updated through two different aliases and the first
+  update physically moves the row, the second update will error
+  because the row is no longer located where expected. This function
+  checks if the multiple-table update is about to do that and if so
+  returns with an error.
+
+  The following update operations physically moves rows:
+    1) Update of a column in a clustered primary key
+    2) Update of a column used to calculate which partition the row belongs to
+
+  This function returns with an error if both of the following are
+  true:
+
+    a) A table in the multiple-table update statement is updated
+       through multiple aliases (including views)
+    b) At least one of the updates on the table from a) may physically
+       moves the row. Note: Updating a column used to calculate which
+       partition a row belongs to does not necessarily mean that the
+       row is moved. The new value may or may not belong to the same
+       partition.
+
+  @param leaves               First leaf table
+  @param tables_for_update    Map of tables that are updated
+
+  @return
+    true   if the update is unsafe, in which case an error message is also set,
+    false  otherwise.
+*/
+static
+bool unsafe_key_update(TABLE_LIST *leaves, table_map tables_for_update)
+{
+  TABLE_LIST *tl= leaves;
+
+  for (tl= leaves; tl ; tl= tl->next_leaf)
+  {
+    if (tl->table->map & tables_for_update)
+    {
+      TABLE *table1= tl->table;
+      bool primkey_clustered= (table1->file->primary_key_is_clustered() &&
+                               table1->s->primary_key != MAX_KEY);
+
+      bool table_partitioned= false;
+#ifdef WITH_PARTITION_STORAGE_ENGINE
+      table_partitioned= (table1->part_info != NULL);
+#endif
+
+      if (!table_partitioned && !primkey_clustered)
+        continue;
+
+      for (TABLE_LIST* tl2= tl->next_leaf; tl2 ; tl2= tl2->next_leaf)
+      {
+        /*
+          Look at "next" tables only since all previous tables have
+          already been checked
+        */
+        TABLE *table2= tl2->table;
+        if (table2->map & tables_for_update && table1->s == table2->s)
+        {
+          // A table is updated through two aliases
+          if (table_partitioned &&
+              (partition_key_modified(table1, table1->write_set) ||
+               partition_key_modified(table2, table2->write_set)))
+          {
+            // Partitioned key is updated
+            my_error(ER_MULTI_UPDATE_KEY_CONFLICT, MYF(0),
+                     tl->belong_to_view ? tl->belong_to_view->alias
+                                        : tl->alias,
+                     tl2->belong_to_view ? tl2->belong_to_view->alias
+                                         : tl2->alias);
+            return true;
+          }
+
+          if (primkey_clustered)
+          {
+            // The primary key can cover multiple columns
+            KEY key_info= table1->key_info[table1->s->primary_key];
+            KEY_PART_INFO *key_part= key_info.key_part;
+            KEY_PART_INFO *key_part_end= key_part + key_info.key_parts;
+
+            for (;key_part != key_part_end; ++key_part)
+            {
+              if (bitmap_is_set(table1->write_set, key_part->fieldnr-1) ||
+                  bitmap_is_set(table2->write_set, key_part->fieldnr-1))
+              {
+                // Clustered primary key is updated
+                my_error(ER_MULTI_UPDATE_KEY_CONFLICT, MYF(0),
+                         tl->belong_to_view ? tl->belong_to_view->alias
+                         : tl->alias,
+                         tl2->belong_to_view ? tl2->belong_to_view->alias
+                         : tl2->alias);
+                return true;
+              }
+            }
+          }
+        }
+      }
+    }
+  }
+  return false;
+}
+
 
 /*
   make update specific preparation and checks after opening tables
@@ -982,9 +1137,17 @@ int mysql_multi_update_prepare(THD *thd)
   /* following need for prepared statements, to run next time multi-update */
   thd->lex->sql_command= SQLCOM_UPDATE_MULTI;
 
-  /* open tables and create derived ones, but do not lock and fill them */
+  /*
+    Open tables and create derived ones, but do not lock and fill them yet.
+
+    During prepare phase acquire only S metadata locks instead of SW locks to
+    keep prepare of multi-UPDATE compatible with concurrent LOCK TABLES WRITE
+    and global read lock.
+  */
   if ((original_multiupdate &&
-       open_tables(thd, &table_list, &table_count, 0)) ||
+       open_tables(thd, &table_list, &table_count,
+                   (thd->stmt_arena->is_stmt_prepare() ?
+                    MYSQL_OPEN_FORCE_SHARED_MDL : 0))) ||
       mysql_handle_derived(lex, &mysql_derived_prepare))
     DBUG_RETURN(TRUE);
   /*
@@ -1019,10 +1182,14 @@ int mysql_multi_update_prepare(THD *thd)
 
   thd->table_map_for_update= tables_for_update= get_table_map(fields);
 
+  leaves= lex->select_lex.leaf_tables;
+
+  if (unsafe_key_update(leaves, tables_for_update))
+    DBUG_RETURN(true);
+
   /*
     Setup timestamp handling and locking mode
   */
-  leaves= lex->select_lex.leaf_tables;
   for (tl= leaves; tl; tl= tl->next_leaf)
   {
     TABLE *table= tl->table;
@@ -1142,7 +1309,11 @@ int mysql_multi_update_prepare(THD *thd)
  
   if (thd->fill_derived_tables() &&
       mysql_handle_derived(lex, &mysql_derived_filling))
+  {
+    mysql_handle_derived(lex, &mysql_derived_cleanup);
     DBUG_RETURN(TRUE);
+  }
+  mysql_handle_derived(lex, &mysql_derived_cleanup);
 
   DBUG_RETURN (FALSE);
 }
@@ -1647,18 +1818,8 @@ bool multi_update::send_data(List<Item> &not_used_values)
     if (table->status & (STATUS_NULL_ROW | STATUS_UPDATED))
       continue;
 
-    /*
-      We can use compare_record() to optimize away updates if
-      the table handler is returning all columns OR if
-      if all updated columns are read
-    */
     if (table == table_to_update)
     {
-      bool can_compare_record;
-      can_compare_record= (!(table->file->ha_table_flags() &
-                             HA_PARTIAL_COLUMN_READ) ||
-                           bitmap_is_subset(table->write_set,
-                                            table->read_set));
       table->status|= STATUS_UPDATED;
       store_record(table,record[1]);
       if (fill_record_n_invoke_before_triggers(thd, *fields_for_table[offset],
@@ -1673,7 +1834,7 @@ bool multi_update::send_data(List<Item> &not_used_values)
       */
       table->auto_increment_field_not_null= FALSE;
       found++;
-      if (!can_compare_record || compare_record(table))
+      if (!records_are_comparable(table) || compare_records(table))
       {
 	int error;
         if ((error= cur_table->view_check_option(thd, ignore)) !=
@@ -1864,7 +2025,6 @@ int multi_update::do_updates()
     DBUG_RETURN(0);
   for (cur_table= update_tables; cur_table; cur_table= cur_table->next_local)
   {
-    bool can_compare_record;
     uint offset= cur_table->shared;
 
     table = cur_table->table;
@@ -1913,11 +2073,6 @@ int multi_update::do_updates()
       goto err;
     }
 
-    can_compare_record= (!(table->file->ha_table_flags() &
-                           HA_PARTIAL_COLUMN_READ) ||
-                         bitmap_is_subset(table->write_set,
-                                          table->read_set));
-
     for (;;)
     {
       if (thd->killed && trans_safe)
@@ -1965,7 +2120,7 @@ int multi_update::do_updates()
                                             TRG_ACTION_BEFORE, TRUE))
         goto err2;
 
-      if (!can_compare_record || compare_record(table))
+      if (!records_are_comparable(table) || compare_records(table))
       {
         int error;
         if ((error= cur_table->view_check_option(thd, ignore)) !=
@@ -2062,7 +2217,9 @@ bool multi_update::send_eof()
      Does updates for the last n - 1 tables, returns 0 if ok;
      error takes into account killed status gained in do_updates()
   */
-  int local_error = (table_count) ? do_updates() : 0;
+  int local_error= thd->is_error();
+  if (!local_error)
+    local_error = (table_count) ? do_updates() : 0;
   /*
     if local_error is not set ON until after do_updates() then
     later carried out killing should not affect binlogging.