A compact Metamorph index maintains knowledge of what rows words occur in, but does not store word position information. In Texis version 7 and later, it is created by adding the index option WORDPOSITIONS 'off' (here). In Texis version 6 and earlier, this was the default Metamorph index type, and was created with CREATE METAMORPH INDEX (no flags/options).
Because of the lack of word position information, a compact
Metamorph index only consumes about 7% of the text size in disk space
(vs. about 20-30% for a Metamorph inverted index); this compact size
can also speed up its usage. However, a post-process search is needed
after index usage if the query needs word-position information
(e.g. to resolve phrases, within "
LIKEP ranking), which can greatly slow such queries. Thus a
compact Metamorph index is best suited to queries that do not need
word position information, such as single non-phrased words with no
special pattern matchers, and no ranking (e.g.
LIKE3 search (below), which never does a
post-search, can also use a compact Metamorph index without loss of