An inverted Metamorph index is the most commonly used type of
Metamorph index, and is created with CREATE METAMORPH INVERTED
INDEX. In Texis version 7 (and
compatibilityversion 7) and
later, this is the default Metamorph index type created when no other
flags are given, e.g. CREATE METAMORPH INDEX; in version 6 (or
compatibilityversion 6), a compact index is created. The
version 7 index option WORDPOSITIONS 'on'
(here) also explicitly creates this type of
Metamorph index (same effect as the
INVERTED flag after
An inverted Metamorph index maintains knowledge not only of what
rows words occur in, but also what position in each row the words
occur in (the
WORDPOSITIONS). With such an index Texis can
often avoid a post-search altogether, because the index contains all
the information needed for phrase resolution and rank computation.
This can speed up searches more than a compact Metamorph index,
especially for ranking queries using
LIKEP, or phrase searches.
Because of the greater range of queries resolvable with an inverted
Metamorph index (vs. compact), in Texis version 7 and later it is the
default Metamorph type created. However, an inverted Metamorph index
consumes more disk space, typically 20-30% of the text size versus
about 7% for a compact Metamorph index. Index updating is also
slower because of this.