2026-03-12 20:23:15

tpt/ast/03_index_density.sql

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+-- Copyright 2018 Tanel Poder. All rights reserved. More info at http://tanelpoder.com
+-- Licensed under the Apache License, Version 2.0. See LICENSE.txt for terms & conditions.
+
+-- analyze index density (how many rows per leaf block)
+-- using SYS_OP_LBID function
+
+-- replace the first argument of SYS_OP_LBID number with the object_id of the index you are scanning
+-- also you need to modify the table name and index name hint to query the table/index of your interest
+-- make sure that the index is actually accessed in the execution plan (both fast full scan and range/full
+-- scans do work, but fast full scan is the fastest if you want to scan through the entire index segment)
+-- 
+-- additionally, you can use SAMPLE BLOCK syntax (below) to sample only some index blocks (when using
+-- fast full scan)
+
+
+COL blocks_histogram HEAD "Log(2,blocks) Histogram" FOR A30
+
+SELECT
+     LPAD(NVL(TO_CHAR(rows_per_block), 'Total:'), 15, ' ') num_rows_in_blk
+   , blocks
+   , NVL2(rows_per_block, LPAD('#', LOG(2,blocks), '#'), null) blocks_histogram
+FROM (
+    SELECT 
+        CEIL(num_rows/10) * 10 rows_per_block
+      , COUNT(*) blocks
+    FROM (
+        SELECT /*+ INDEX_FFS(o IDX3_INDEXED_OBJECTS) */ 
+            count(*)                            num_rows
+        FROM 
+            indexed_objects o  -- SAMPLE BLOCK (1000) o
+        WHERE 
+            owner IS NOT NULL 
+        GROUP BY 
+            SYS_OP_LBID( 78363, 'L', o.ROWID)
+    )
+    GROUP BY ROLLUP 
+       ( CEIL(num_rows/10) * 10 )
+    ORDER BY
+        CEIL(num_rows/10) * 10 
+)
+/
+
+