MAXIMUM TERM LENGTH clause - Set the maximum term length

The MAXIMUM TERM LENGTH setting is used differently depending on the term breaker algorithm.

The value of MAXIMUM TERM LENGTH must be less than or equal to 60. If you set it lower than the MINIMUM TERM LENGTH, then MINIMUM TERM LENGTH is automatically adjusted to be equal to MAXIMUM TERM LENGTH.

If not defined, the default for MAXIMUM TERM LENGTH is taken from the setting in the default text configuration object, which is typically 20.

The following table explains the impact that the value of MAXIMUM TERM LENGTH has on text indexing and on how query strings are handled:

Text indexes Query strings

  • GENERIC text indexes   For GENERIC text indexes, MAXIMUM TERM LENGTH specifies the maximum length, in characters, for terms inserted in the text index.

  • NGRAM text index   For NGRAM text indexes, MAXIMUM TERM LENGTH determines the length of the n-grams that terms are broken into. An appropriate choice of length for n-grams depends on the language. Typical values are 4 or 5 characters for English, and 2 or 3 characters for Chinese.

  • GENERIC text indexes   For GENERIC text indexes, query terms longer than MAXIMUM TERM LENGTH are ignored because they cannot exist in the text index.

  • NGRAM text index   For NGRAM text indexes, query terms are broken into n-grams of length n, where n is the same as MAXIMUM TERM LENGTH. Then, the database server uses the n-grams to search the text index. Terms shorter than MAXIMUM TERM LENGTH are ignored because they will not match the n-grams in the text index. Therefore, proximity searches do not work unless arguments are prefixes of length n.

 See also
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