2026-03-12 20:23:15

tpt/demos/find_hash_collision.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.
+
+--------------------------------------------------------------------------------
+--
+-- File name:   demos/find_hash_collision.sql
+-- Purpose:     Advanced Oracle Troubleshooting seminar demo script
+--              for finding different SQL statements which have colliding hash
+--              values
+--
+-- Author:      Tanel Poder
+-- Copyright:   (c) http://www.tanelpoder.com
+--              
+-- Usage:       @demos/find_hash_collision.sql
+-- 	        
+-- Other:       In theory it may take a lot of memory if iterating way too many
+--              times before finding colliding hash value
+--
+-- NB! This script is not working properly yet! As GET_SQL_HASH function
+--     isn't doing its job right
+--
+--------------------------------------------------------------------------------
+
+SET SERVEROUT ON SIZE 1000000
+
+DECLARE
+    TYPE typ IS TABLE OF NUMBER INDEX BY VARCHAR2(10);
+    t typ;
+    i NUMBER := 0;
+    h VARCHAR2(10);
+    tmp NUMBER;
+    tmp_raw RAW(16);
+    str VARCHAR2(100):='select * from dual where rownum = ';
+BEGIN
+    WHILE TRUE LOOP
+        h := TO_CHAR(DBMS_UTILITY.GET_SQL_HASH(str||TO_CHAR(i), tmp_raw, tmp));    
+
+        IF t.EXISTS(h) THEN
+            DBMS_OUTPUT.PUT_LINE(CHR(10)||'Matching hash values found (hash='||TO_CHAR(h)||'):'||CHR(10)||CHR(10)||str||TO_CHAR(t(h))||CHR(10)||str||TO_CHAR(i));
+            DBMS_OUTPUT.PUT_LINE('raw='||RAWTOHEX(tmp_raw));
+            EXIT;
+        ELSE
+           t(h):=i;
+           i:=i+1;
+        END IF;
+    END LOOP;
+END;
+/
+
+SET SERVEROUT OFF