cleanup: stat tables

don't allocate Column_statistics_collected objects that won't
be used.

minor style fixes (StringBuffer<>, etc)

sql/sql_statistics.cc

@@ -1042,15 +1042,15 @@ class Column_stat: public Stat_table
 
   void store_stat_fields()
   {
-    char buff[MAX_FIELD_WIDTH];
-    String val(buff, sizeof(buff), &my_charset_bin);
+    StringBuffer<MAX_FIELD_WIDTH> val;
 
     MY_BITMAP *old_map= dbug_tmp_use_all_columns(stat_table, &stat_table->read_set);
 
     for (uint i= COLUMN_STAT_MIN_VALUE; i <= COLUMN_STAT_HISTOGRAM; i++)
     {  
       Field *stat_field= stat_table->field[i];
-      if (table_field->collected_stats->is_null(i))
+      Column_statistics *stats= table_field->collected_stats;
+      if (stats->is_null(i))
         stat_field->set_null();
       else
       {
@@ -1058,10 +1058,10 @@ class Column_stat: public Stat_table
         switch (i) {
         case COLUMN_STAT_MIN_VALUE:
           if (table_field->type() == MYSQL_TYPE_BIT)
-            stat_field->store(table_field->collected_stats->min_value->val_int(),true);
+            stat_field->store(stats->min_value->val_int(),true);
           else
           {
-            table_field->collected_stats->min_value->val_str(&val);
+            stats->min_value->val_str(&val);
             uint32 length= Well_formed_prefix(val.charset(), val.ptr(),
                            MY_MIN(val.length(), stat_field->field_length)).length();
             stat_field->store(val.ptr(), length, &my_charset_bin);
@@ -1069,37 +1069,33 @@ class Column_stat: public Stat_table
           break;
         case COLUMN_STAT_MAX_VALUE:
           if (table_field->type() == MYSQL_TYPE_BIT)
-            stat_field->store(table_field->collected_stats->max_value->val_int(),true);
+            stat_field->store(stats->max_value->val_int(),true);
           else
           {
-            table_field->collected_stats->max_value->val_str(&val);
+            stats->max_value->val_str(&val);
             uint32 length= Well_formed_prefix(val.charset(), val.ptr(),
                             MY_MIN(val.length(), stat_field->field_length)).length();
             stat_field->store(val.ptr(), length, &my_charset_bin);
           }
           break;
         case COLUMN_STAT_NULLS_RATIO:
-          stat_field->store(table_field->collected_stats->get_nulls_ratio());
+          stat_field->store(stats->get_nulls_ratio());
           break;
         case COLUMN_STAT_AVG_LENGTH:
-          stat_field->store(table_field->collected_stats->get_avg_length());
+          stat_field->store(stats->get_avg_length());
           break;
         case COLUMN_STAT_AVG_FREQUENCY:
-          stat_field->store(table_field->collected_stats->get_avg_frequency());
+          stat_field->store(stats->get_avg_frequency());
           break; 
         case COLUMN_STAT_HIST_SIZE:
-          stat_field->store(table_field->collected_stats->histogram.get_size());
+          stat_field->store(stats->histogram.get_size());
           break;
         case COLUMN_STAT_HIST_TYPE:
-          stat_field->store(table_field->collected_stats->histogram.get_type() +
-                            1);
+          stat_field->store(stats->histogram.get_type() + 1);
           break;
         case COLUMN_STAT_HISTOGRAM:
-          const char * col_histogram=
-          (const char *) (table_field->collected_stats->histogram.get_values());
-	  stat_field->store(col_histogram,
-                            table_field->collected_stats->histogram.get_size(),
-                            &my_charset_bin);
+	  stat_field->store((char *)stats->histogram.get_values(),
+                            stats->histogram.get_size(), &my_charset_bin);
           break;           
         }
       }
@@ -2100,20 +2096,24 @@ void create_min_max_statistical_fields_for_table_share(THD *thd,
 int alloc_statistics_for_table(THD* thd, TABLE *table)
 { 
   Field **field_ptr;
-  uint fields;
 
   DBUG_ENTER("alloc_statistics_for_table");
 
+  uint columns= 0;
+  for (field_ptr= table->field; *field_ptr; field_ptr++)
+  {
+    if (bitmap_is_set(table->read_set, (*field_ptr)->field_index))
+      columns++;
+  }
 
   Table_statistics *table_stats= 
     (Table_statistics *) alloc_root(&table->mem_root,
                                     sizeof(Table_statistics));
 
-  fields= table->s->fields ; 
   Column_statistics_collected *column_stats=
     (Column_statistics_collected *) alloc_root(&table->mem_root,
                                     sizeof(Column_statistics_collected) *
-				    (fields+1));
+				    columns);
 
   uint keys= table->s->keys;
   Index_statistics *index_stats=
@@ -2124,12 +2124,6 @@ int alloc_statistics_for_table(THD* thd, TABLE *table)
   ulonglong *idx_avg_frequency= (ulonglong*) alloc_root(&table->mem_root,
                                                sizeof(ulonglong) * key_parts);
 
-  uint columns= 0;
-  for (field_ptr= table->field; *field_ptr; field_ptr++)
-  {
-    if (bitmap_is_set(table->read_set, (*field_ptr)->field_index))
-      columns++;
-  }
   uint hist_size= thd->variables.histogram_size;
   Histogram_type hist_type= (Histogram_type) (thd->variables.histogram_type);
   uchar *histogram= NULL;
@@ -2151,9 +2145,9 @@ int alloc_statistics_for_table(THD* thd, TABLE *table)
   table_stats->idx_avg_frequency= idx_avg_frequency;
   table_stats->histograms= histogram;
   
-  memset(column_stats, 0, sizeof(Column_statistics) * (fields+1));
+  memset(column_stats, 0, sizeof(Column_statistics) * columns);
 
-  for (field_ptr= table->field; *field_ptr; field_ptr++, column_stats++)
+  for (field_ptr= table->field; *field_ptr; field_ptr++)
   {
     if (bitmap_is_set(table->read_set, (*field_ptr)->field_index))
     {
@@ -2161,7 +2155,7 @@ int alloc_statistics_for_table(THD* thd, TABLE *table)
       column_stats->histogram.set_type(hist_type);
       column_stats->histogram.set_values(histogram);
       histogram+= hist_size;
-      (*field_ptr)->collected_stats= column_stats;
+      (*field_ptr)->collected_stats= column_stats++;
     }
   }