[SQL] Ooops ! :( Recovery techniques

[Richard Sydney-Smith]

My machine just crashed in the middle of an update.   When I restart the postgresql server the database engine appears ok and then tells me that a file /data/pg_clog/0697 is not there.   I presume that these are the transaction log files. I would like to truncate the old logfiles, re-index and keep going. I that possible with postgres of do I have to do a full rebuild?   thanks verymuch   Richard Sydney-Smith