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=head1 pgestraier - PostgreSQL full-text search using Hyper Estraier |
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This package is essentially composed of two different parts: |
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=over 4 |
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=item search function |
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PostgreSQL function to search Hyper Estraier full-text index, using |
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full-text queries and attribute filtering to return user-specified |
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table of results. |
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This function can mimic SQL C<LIMIT>, C<OFFSET> and C<ORDER BY> |
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functionality much faster than using those SQL constructs on search |
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results. |
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=item trigger function |
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PostgreSQL trigger function to keep Hyper Estraier in sync with PostgreSQL. |
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It triggers after insert, update or delete and update full-text index |
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accordingly. |
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=back |
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Both functions are written in C, while test framework and supporting |
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utilities are written in perl. |
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You can use just one of those functions. If you want just to search existing |
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Hyper Estraier index or generate it off-line (after nightly batch jobs, for |
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example), just use search function. |
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On the other hand, if you want just to keep your Hyper Estraier index in |
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sync with PostgreSQL data, you can use just trigger function to achieve that. |
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=head1 Why is it written? |
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Aside from providing single query language (SQL) to RDBMS and full text index |
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(using any language that has PostgreSQL client libraries), real power is |
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hidden in ability to join results from full text index and structured data |
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in RDBMS. |
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For simple real-life example which address problem |
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C<< WHERE name LIKE '%foo%' OR surname LIKE '%foo%' >> |
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is slow see L<Tutorial> and L<pgest-index> documentation. |
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=head1 How to install |
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Installation should be simple. However, you will have to have following |
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software already installed before you try this functions: |
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=over |
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=item * |
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PostgreSQL (tested with versions 7.4, 8.0 and 8.1) with development libraries |
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=item * |
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Hyper Estraier (tested with various versions, recommended 1.2.4 or newer) |
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with development headers |
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=item * |
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working C compiler (tested with gcc) |
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=back |
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If you want to use helper script to create consistency triggers to keep |
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Hyper Estraier in sync with PostgreSQL database, you will also need: |
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=over |
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=item * |
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working perl installation |
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=item * |
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perl modules C<Search::Estraier>, C<DBI> and C<DBD::Pg> |
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=back |
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To run tests you will also need: |
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=over |
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=item * |
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perl module C<Test::More> |
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=item * |
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C<trivia.list.gz> from Internet Movie Database in C<data/> directory. |
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You can download it from L<http://www.imdb.com/interfaces> |
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=item * |
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PostgreSQL database C<test> with permissions for current user |
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=item * |
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Hyper Estraier C<estmaster> running with permissions for C<admin> user |
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to create C<trivia> node. |
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=back |
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If you have all that, you should be able to type |
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make |
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and see sample results. You will be asked your password once (via sudo) to |
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install C<pgest.so> shared library in system-wide location so that PostgreSQL |
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could access it. |
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=head2 Create sample index using Hyper Estraier perl bindings |
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Perl bindings for Hyper Estraier are available at CPAN: |
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L<http://search.cpan.org/~dpavlin/Search-Estraier/> |
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After installing C<Search::Estraier> you can create index using following commands: |
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cd data |
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make index |
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cd .. |
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To run tests (which require that you have estcmd in your $PATH) issue |
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make test |
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See also included file C<test.sql> for more examples of usage. |
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=head1 Usage of search function pgest from SQL |
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C<pgest> PostgreSQL function tries to mimic usage of normal database tables (with support for attribute filtering, limit and offset) in following way: |
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SELECT |
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-- columns to return (defined later) |
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id,title,size |
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FROM pgest( |
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-- node URI, login, password and depth of search |
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'http://localhost:1978/node/trivia', 'admin', 'admin', 42, |
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-- query |
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'blade runner', |
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-- additional attributes, use NULL or '' to disable |
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-- multiple attributes conditions can be separated by {{!}} |
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'@title ISTRINC blade', |
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-- order results by |
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'@title STRA', |
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-- limit, use NULL or 0 to disable |
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null, |
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-- offset, use NULL or 0 to disable |
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null, |
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-- attributes to return as columns |
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ARRAY['@id','@title','@size'] |
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) AS ( |
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-- specify names and types of returned attributes |
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id text, title text, size text |
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); |
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You should note that Hyper Estraier uses UTF-8 encoding, while your |
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PostgreSQL installation might use different encoding. To fix that, use |
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C<convert> function in PostgreSQL to convert encodings. |
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=head2 Using index via C<estmaster> server process |
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This is default and recommended way to use C<pgest> functionality. In this |
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case, C<pgest> will use node API and access index through C<estmaster> |
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process which should be running on (local or remote) machine. |
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This will remove database opening overhead, at a cost of (small) additional network |
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traffic. However, you can have Hyper Estraier C<estmaster> process running on |
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different machine or update index while doing searches, so benefits of this |
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approach are obvious. |
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=head2 Accessing database directly |
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B<Please note that direct access to database is depreciated.> As such, it's |
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not stated in example, and it's kept just for backward compatibility, but it |
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will probably be removed in future versions of C<pgest>. |
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If you want to access database directly (without running C<estmaster> process), you |
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have to replace node URI, login, password and depth with full path to database file. |
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Have in mind that C<postgres> user under which PostgreSQL is running must |
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have read permission on Hyper Estraier database files. |
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This will work a bit faster on really small indexes. However, when your |
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index grows bigger, you might consider using node API to remove overhead of |
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database opening on each query. |
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=head1 Usage of trigger function pgest_trigger from SQL |
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Let's first say that I really suggest that you use C<dbi-index.pl> helper script to |
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create triggers because it already supports following steps automatically: |
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=over |
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=item begin transaction |
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Transaction is needed to catch updates which might happen while creation |
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of full-text index is in progress (and on huge collections this can take a while, |
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just like normal index creation in PostgreSQL). |
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=item insert all existing data in full-text index |
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This will be done directly from PostgreSQL database to Hyper Estraier index. |
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This is somewhat faster than waiting for trigger to fire for each existing |
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row. |
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=item create insert, update and delete triggers |
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Which will keep data in sync later |
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=item commit transaction |
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=back |
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If you still want to do that manually, you will need to know format of |
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C<pgest_trigger> function: |
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CREATE TRIGGER pgest_trigger_insert AFTER INSERT |
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ON table FOR EACH ROW |
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EXECUTE PROCEDURE pgest_trigger( |
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-- node URI, login and password |
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'http://localhost:1978/node/trivia', 'admin', 'admin', |
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-- name of primary key column |
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'id', |
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-- names of all other columns to index (one or more) |
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'column', 'another_one', 'and_another' |
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) |
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You have to create triggers for C<UPDATE> and C<DELETE> in similar way. |
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=head1 Who wrote this? |
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Hyper Estraier is written by Mikio Hirabayashi. |
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PostgreSQL is written by hackers calling themselves PostgreSQL Global |
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Development Group. |
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This small C functions are written by L<Dobrica Pavlinusic|http://www.rot13.org/~dpavlin/>, dpavlin@rot13.org. |
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=head1 See also |
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=over |
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=item * |
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L<Tutorial> - how to create first full-text index in under 10 minutes! |
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=item * |
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L<ChangeLog> - what has changed since last version |
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=item * |
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L<pgest-index> - helper script to create index and triggers |
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=item * |
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L<pgFoundry|http://pgfoundry.org/projects/pgestraier/> hosts home page of this project |
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=item * |
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L<Hyper Estraier user guide|http://hyperestraier.sourceforge.net/uguide-en.html#searchcond> |
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has a documentaton about query format. C<pgestraier> is using noraml queries (with |
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C<AND>, C<OR> etc.) and not simplified queryies (with C<|>). |
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=back |