# Gavin Andresen
# 2010-09-27 19:40:20
# https://bitcointalk.org/index.php?topic=724.msg14297#msg14297

blkindex.dat contains all the transactions, in records that look like: @p{brk}
  key:  "tx" + HASH_OF_TRANSACTION @p{brk}
  value: serialized CTxIndex @p{par}

The CTxIndex points to a record in one of the blk000n.dat files. @p{par}

That does bring up an interesting point, though:  if lightweight clients are implemented, they wouldn't be able to support an arbitrary 'gettransaction'. @p{brk}