title: postgresql data recovery after multiply rows update
body: <p>I am trying to retrieve data lost on wrong update query, using   xlog and pg_xlogdump tool.</p>
  
  <p>The query was the following:<br>
  update table set column1 =21 where column2 > column3 ( 1 condition was missed, so more rows were updated )</p>
  
  <p>Example of 1 update record shown below. It starts with 1 update line and 5 insert lines. 
  I wonder is there any way to find the number  replaced with 21?</p>
  
  <p>1) First line ( update)  rel 1663/5880305/5880686 shows exactly the table I am looking for (5880305 oid of the db and 5880686 oid of the table)
  Also I have old backup and  row with tuple 47275/8 there is the same row that was updated, with new tuple in updated version ( new tid : 293804/16 )</p>
  
  <p>2) 4th line shows column1 update (11996103 is oid of that column ) , however I don't know
  how to find tuple 302/164 and how to retrieve the lost number </p>
  
  <p>Thanks in advance.</p>
  
  <pre><code>rmgr: Heap        len (rec/tot):    163/  8391, tx:  692554090, lsn: 115/73F1D288, prev 115/73F1D240, bkp: 1000, desc: update: rel 1663/5880305/5880686; tid 47275/8 xmax 692554090 ; new tid 293804/16 xmax 0
  backup bkp #0; rel 1663/5880305/5880686; fork: main; block: 47275; hole: offset: 228, length: 20
  
  rmgr: Btree       len (rec/tot):     34/    66, tx:  692554090, lsn: 115/73F1F368, prev 115/73F1D288, bkp: 0000, desc: insert: rel 1663/5880305/11995979; tid 6587/293
  
  rmgr: Btree       len (rec/tot):     34/    66, tx:  692554090, lsn: 115/73F1F3B0, prev 115/73F1F368, bkp: 0000, desc: insert: rel 1663/5880305/11996093; tid 6587/292
  
  rmgr: Btree       len (rec/tot):     34/    66, tx:  692554090, lsn: 115/73F1F3F8, prev 115/73F1F3B0, bkp: 0000, desc: insert: rel 1663/5880305/11996103; tid 302/164
  
  rmgr: Btree       len (rec/tot):     34/    66, tx:  692554090, lsn: 115/73F1F440, prev 115/73F1F3F8, bkp: 0000, desc: insert: rel 1663/5880305/11996135; tid 43502/2
  
  rmgr: Btree       len (rec/tot):     34/    66, tx:  692554090, lsn: 115/73F1F488, prev 115/73F1F440, bkp: 0000, desc: insert: rel 1663/5880305/11996136; tid 1/2
  </code></pre>