2026-03-12 20:23:15

mhouri/h_hist1.sql

@@ -0,0 +1,80 @@
+/* ----------------------------------------------------------------------------------|
+|Author : Mohamed Houri                                                              |
+|Date   : 03/07/2020                                                                 |
+|Scope  : This script gives historical column histogram values                       |
+|          -- I am using sys.WRI$_OPTSTAT_HISTHEAD_HISTORY for this purpose			 |		
+|          -- I am only able to say whether, previously, there was HISTOGRAM or not  |
+|          -- I can't show the historical type of Histogram 				         |
+|																					 |
+|Usage  :  SQL> @h_hist1                                                             |
+|			Enter value for table_name: t1                                           |
+|			Enter value for owner: test                                              |
+|			Enter value for col_name: n2     				                         |
+-------------------------------------------------------------------------------------|*/
+col object_name   	    format a20
+col column_name  		format a12
+col last_analyzed 		format a20
+col prev_last_analyzed  format a20
+col histogram           format a16
+col prev_histogram      format a16
+WITH sq AS 
+    (
+     SELECT
+	      object_id
+		 ,object_name
+		 ,subobject_name
+	 FROM
+	     dba_objects
+	 WHERE
+	     object_name    = upper ('&&table_name')
+	 AND owner          = upper('&&owner')
+	 AND subobject_name IS NULL
+	 )
+SELECT
+	 object_name
+	,column_name
+	,lead(prev_histogram,1,histogram) over (order by last_analyzed) histogram
+	,last_analyzed
+	,prev_histogram
+	,prev_last_analyzed
+FROM
+   (
+     SELECT
+	     object_name
+		,column_name
+		,(select histogram from all_tab_col_statistics where owner = upper('&&owner') 
+		  and table_name = upper('&&table_name') and column_name = upper('&&col_name')) histogram
+		,last_analyzed
+		,stat_time prev_last_analyzed
+		,row_number() over (order by last_analyzed) rn
+		,case when round(derivedDensity,9)= round(density,9) then 'NONE' else 'HISTOGRAM' end prev_histogram
+	 FROM
+	    (
+		 SELECT
+		     object_name
+			,column_name
+			,to_char(savtime ,'dd/mm/yyyy hh24:mi:ss')     last_analyzed
+			,to_char(timestamp# ,'dd/mm/yyyy hh24:mi:ss') stat_time
+			,density
+			,1/distcnt derivedDensity
+			,row_number() over (order by savtime) rn
+			,lag(case when round(1/distcnt,9) = round(density,9) then 'NONE' else 'HISTOGRAM' end) over(order by savtime) hist_histogram
+		 FROM
+		    sys.WRI$_OPTSTAT_HISTHEAD_HISTORY
+			INNER JOIN sq ON object_id = obj#
+			INNER JOIN (SELECT 
+			                column_id
+						   ,column_name
+						FROM
+						    dba_tab_columns
+						WHERE
+						    column_name = upper('&&col_name')
+						AND table_name  = upper('&&table_name') 
+			            AND owner       = upper('&&owner')
+						) ON intcol# = column_id
+	)
+WHERE
+   rn >= 1 --exlcude/include the very first dbms_stat
+   )
+ORDER BY
+    last_analyzed;