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Learning PostgreSQL 11 - Third Edition
book

Learning PostgreSQL 11 - Third Edition

by Christopher Travers, Andrey Volkov
January 2019
Beginner
556 pages
14h 19m
English
Packt Publishing
Content preview from Learning PostgreSQL 11 - Third Edition

Pattern matching

Pattern matching is the act of checking a given sequence of words for the presence of the constituents of some pattern. There are several factors that affect the result of pattern matching, including the following:

  • Text normalization
  • Dictionary
  • Ranking and weight
  • How often query terms occur in the document
  • Distance between the term's occurrence
  • Document size

If the text isn't normalized, a text search might not return the expected result. The following examples show how pattern matching can fail with unnormalized text:

postgres=# SELECT 'elephants'::tsvector @@ 'elephant'; ?column? ---------- f(1 row)

In the preceding query, casting elephants to tsvector and the implicit casting of elephant to the query doesn't generate ...

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Publisher Resources

ISBN: 9781789535464