Fixed bug mdev-11488.

The patch for bug mdev-10882 tried to fix it by providing an
implementation of the virtual method build_clone for the class
Item_cache. It's turned out that it is not easy provide a valid
implementation for Item_cache::build_clone(). At the same time
if the condition that can be pushed into a materialized view
contains a cached item this item can be substituted for a basic
constant of the same value. In such a way we can avoid building
proper clones for Item_cache objects when constructing pushdown
conditions.

1 files changed, 73 insertions, 0 deletions

diff --git a/sql/item.cc b/sql/item.cc
index 880275ec997..ead45f84305 100644
--- a/sql/item.cc
+++ b/sql/item.cc
@@ -9406,6 +9406,17 @@ int Item_cache_int::save_in_field(Field *field, bool no_conversions)
 }
 
 
+Item *Item_cache_int::convert_to_basic_const_item(THD *thd)
+{
+  Item *new_item;
+  DBUG_ASSERT(value_cached || example != 0);
+  new_item= null_value ?
+            (Item*) new (thd->mem_root) Item_null(thd) :
+	    (Item*) new (thd->mem_root) Item_int(thd, val_int(), max_length);
+  return new_item;
+} 
+
+
 Item_cache_temporal::Item_cache_temporal(THD *thd,
                                          enum_field_types field_type_arg):
   Item_cache_int(thd, field_type_arg)
@@ -9561,6 +9572,23 @@ Item *Item_cache_temporal::clone_item(THD *thd)
 }
 
 
+Item *Item_cache_temporal::convert_to_basic_const_item(THD *thd)
+{
+  Item *new_item;
+  DBUG_ASSERT(value_cached || example != 0);
+  if (null_value)
+    new_item= (Item*) new (thd->mem_root) Item_null(thd);
+  else
+  {
+    MYSQL_TIME ltime;
+    unpack_time(val_datetime_packed(), &ltime);
+    new_item= (Item*) new (thd->mem_root) Item_datetime_literal(thd, &ltime,
+                                                                decimals);
+  }
+  return new_item;
+}
+
+
 bool Item_cache_real::cache_value()
 {
   if (!example)
@@ -9609,6 +9637,18 @@ my_decimal *Item_cache_real::val_decimal(my_decimal *decimal_val)
 }
 
 
+Item *Item_cache_real::convert_to_basic_const_item(THD *thd)
+{
+  Item *new_item;
+  DBUG_ASSERT(value_cached || example != 0);
+  new_item= null_value ?
+            (Item*) new (thd->mem_root) Item_null(thd) :
+	    (Item*) new (thd->mem_root) Item_float(thd, val_real(),
+                                                   decimals);
+  return new_item;
+} 
+
+
 bool Item_cache_decimal::cache_value()
 {
   if (!example)
@@ -9660,6 +9700,19 @@ my_decimal *Item_cache_decimal::val_decimal(my_decimal *val)
 }
 
 
+Item *Item_cache_decimal::convert_to_basic_const_item(THD *thd)
+{
+  Item *new_item;
+  my_decimal decimal_value;
+  my_decimal *result= val_decimal(&decimal_value);
+  DBUG_ASSERT(value_cached || example != 0);
+  new_item= null_value ?
+            (Item*) new (thd->mem_root) Item_null(thd) :
+	    (Item*) new (thd->mem_root) Item_decimal(thd, result);
+  return new_item;
+} 
+
+
 bool Item_cache_str::cache_value()
 {
   if (!example)
@@ -9739,6 +9792,26 @@ bool Item_cache_row::allocate(THD *thd, uint num)
 }
 
 
+Item *Item_cache_str::convert_to_basic_const_item(THD *thd)
+{
+  Item *new_item;
+  char buff[MAX_FIELD_WIDTH];
+  String tmp(buff, sizeof(buff), value->charset());
+  String *result= val_str(&tmp);
+  DBUG_ASSERT(value_cached || example != 0);
+  if (null_value)
+    new_item= (Item*) new (thd->mem_root) Item_null(thd);
+  else
+  {
+    uint length= result->length();
+    char *tmp_str= thd->strmake(result->ptr(), length);
+    new_item= new (thd->mem_root) Item_string(thd, tmp_str, length,
+                                              result->charset());
+  }
+  return new_item;
+}
+
+
 bool Item_cache_row::setup(THD *thd, Item *item)
 {
   example= item;