Performed re-factoring and re-structuring of the code for mwl#248:

  - Moved the definitions of the classes to store data from persistent
    statistical tables into statistics.h, leaving in other internal 
    data structures only references to the corresponding objects.
  - Defined class Column_statistics_collected derived from the class
    Column_statistics. This is a helper class to collect statistics
    on columns.
  - Moved references to read statistics to TABLE SHARE, leaving the
    the reference to the collected statistics in TABLE.
 - Added a new clone method for the class Field allowing to clone
    fields attached to table shares. It was was used to create 
    fields for min/max values in the memory of the table share.
A lso:
  - Added procedures to allocate memory for statistical data in
    the table share memory and in table memory.
Also: 
  - Added a test case demonstrating how ANALYZE could work in parallel
    to collect statistics on different indexes of the same table.
  - Added a test two demonstrate how two connections working 
    simultaneously could allocate memory for statistical data in the 
    table share memory.  
   

1 files changed, 11 insertions, 14 deletions

diff --git a/sql/table.h b/sql/table.h
index b9a256b132b..e52a1858916 100644
--- a/sql/table.h
+++ b/sql/table.h
@@ -45,6 +45,7 @@ struct TABLE_LIST;
 class ACL_internal_schema_access;
 class ACL_internal_table_access;
 class Field;
+class Table_statistics;
 
 /*
   Used to identify NESTED_JOIN structures within a join (applicable only to
@@ -577,6 +578,15 @@ struct TABLE_SHARE
   KEY  *key_info;			/* data of keys in database */
   uint	*blob_field;			/* Index to blobs in Field arrray*/
 
+  bool stats_can_be_read;      /* Memory for statistical data is allocated */
+  bool stats_is_read;          /* Statistical data for table has been read
+                                  from statistical tables */   
+  /*
+    This structure is used for statistical data on the table
+    that has been read from the statistical table table_stat
+  */ 
+  Table_statistics *read_stats;
+
   uchar	*default_values;		/* row with default values */
   LEX_STRING comment;			/* Comment about table */
   CHARSET_INFO *table_charset;		/* Default charset of string fields */
@@ -1007,24 +1017,11 @@ public:
   */
   query_id_t	query_id;
 
-  /* Statistical data on a table */
-  class Table_statistics
-  {
-  public:
-    my_bool cardinality_is_null;  /* TRUE if the cardinality is unknown */
-    ha_rows cardinality;          /* Number of rows in the table        */
-  };
-
-  /*
-    This structure is used for statistical data on the table
-    that has been read from the statistical table table_stat
-  */ 
-  Table_statistics read_stat;
   /*
     This structure is used for statistical data on the table that
     is collected by the function collect_statistics_for_table
   */
-  Table_statistics write_stat;
+  Table_statistics *collected_stats;
 
   /* The estimate of the number of records in the table used by optimizer */ 
   ha_rows used_stat_records;