Bug#11761296: 53775: QUERY ON PARTITIONED TABLE RETURNS CACHED

                                        RESULT FROM PREVIOUS TRANSACTION

The current Query Cache API is not fully compatible with
the partitioning engine.

There is no good way to implement support for QC due to:
1) a static callback for ha_partition would need to have access
to all partition names and call the underlying callback for each
[sub]partition with the correct name.
2) pruning would be impossible, even if one used the ulonglong
engine_data due to if engine_data is changed, the table is
invalidated by the QC.

So the only viable solution to avoid incorrect data is to not allow
caching of queries using partitioned tables.

(There are some extra changes, due to removal of \r as line break)

2 files changed, 31 insertions, 17 deletions

diff --git a/sql/ha_partition.cc b/sql/ha_partition.cc
index 7c7cf5a4302..7e044b5260e 100644
--- a/sql/ha_partition.cc
+++ b/sql/ha_partition.cc
@@ -6494,20 +6494,20 @@ int ha_partition::add_index(TABLE *table_arg, KEY *key_info, uint num_of_keys)
   return ret;
 err:
   if (file > m_file)
-  {

-    uint *key_numbers= (uint*) ha_thd()->alloc(sizeof(uint) * num_of_keys);

-    KEY *old_key_info= table_arg->key_info;

-    uint i;

-    /* Use the newly added key_info as table->key_info to remove them. */

-    for (i= 0; i < num_of_keys; i++)

-      key_numbers[i]= i;

-    table_arg->key_info= key_info;

-    while (--file >= m_file)

-    {

-      (void) (*file)->prepare_drop_index(table_arg, key_numbers, num_of_keys);

-      (void) (*file)->final_drop_index(table_arg);

-    }

-    table_arg->key_info= old_key_info;

+  {
+    uint *key_numbers= (uint*) ha_thd()->alloc(sizeof(uint) * num_of_keys);
+    KEY *old_key_info= table_arg->key_info;
+    uint i;
+    /* Use the newly added key_info as table->key_info to remove them. */
+    for (i= 0; i < num_of_keys; i++)
+      key_numbers[i]= i;
+    table_arg->key_info= key_info;
+    while (--file >= m_file)
+    {
+      (void) (*file)->prepare_drop_index(table_arg, key_numbers, num_of_keys);
+      (void) (*file)->final_drop_index(table_arg);
+    }
+    table_arg->key_info= old_key_info;
   }
   return ret;
 }
diff --git a/sql/ha_partition.h b/sql/ha_partition.h
index 46e2f447a47..813c0ae8960 100644
--- a/sql/ha_partition.h
+++ b/sql/ha_partition.h
@@ -219,9 +219,9 @@ public:
   */
     ha_partition(handlerton *hton, TABLE_SHARE * table);
     ha_partition(handlerton *hton, partition_info * part_info);
-    ha_partition(handlerton *hton, TABLE_SHARE *share,

-                 partition_info *part_info_arg,

-                 ha_partition *clone_arg,

+    ha_partition(handlerton *hton, TABLE_SHARE *share,
+                 partition_info *part_info_arg,
+                 ha_partition *clone_arg,
                  MEM_ROOT *clone_mem_root_arg);
    ~ha_partition();
   /*
@@ -553,6 +553,20 @@ public:
   virtual int extra(enum ha_extra_function operation);
   virtual int extra_opt(enum ha_extra_function operation, ulong cachesize);
   virtual int reset(void);
+  /*
+    Do not allow caching of partitioned tables, since we cannot return
+    a callback or engine_data that would work for a generic engine.
+  */
+  virtual my_bool register_query_cache_table(THD *thd, char *table_key,
+                                             uint key_length,
+                                             qc_engine_callback
+                                               *engine_callback,
+                                             ulonglong *engine_data)
+  {
+    *engine_callback= NULL;
+    *engine_data= 0;
+    return FALSE;
+  }
 
 private:
   static const uint NO_CURRENT_PART_ID;