Re: new function for tsquery creartion

From: Dmitry Ivanov <d(dot)ivanov(at)postgrespro(dot)ru>
To: Thomas Munro <thomas(dot)munro(at)enterprisedb(dot)com>
Cc: Aleksandr Parfenov <a(dot)parfenov(at)postgrespro(dot)ru>, David Steele <david(at)pgmasters(dot)net>, Aleksander Alekseev <a(dot)alekseev(at)postgrespro(dot)ru>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>
Subject: Re: new function for tsquery creartion
Date: 2018-03-27 22:29:48
Message-ID: 9153fb21831d0ba7c832960f37df2688@postgrespro.ru
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Hi everyone,

I'd like to share some intermediate results. Here's what has changed:

1. OR operator is now case-insensitive. Moreover, trailing whitespace is
no longer used to identify it:

select websearch_to_tsquery('simple', 'abc or');
websearch_to_tsquery
----------------------
'abc' & 'or'
(1 row)

select websearch_to_tsquery('simple', 'abc or(def)');
websearch_to_tsquery
----------------------
'abc' | 'def'
(1 row)

select websearch_to_tsquery('simple', 'abc or!def');
websearch_to_tsquery
----------------------
'abc' | 'def'
(1 row)

2. AROUND(N) has been dropped. I hope that <N, M> operator will allow us
to implement it with a few lines of code.

3. websearch_to_tsquery() now tolerates various syntax errors, for
instance:

Misused operators:

'abc &'
'| abc'
'<- def'

Missing parentheses:

'abc & (def <-> (cat or rat'

Other sorts of nonsense:

'abc &--|| def' => 'abc' & !!'def'
'abc:def' => 'abc':D & 'ef'

This, however, doesn't mean that the result will always be adequate (who
would have thought?). Overall, current implementation follows the GIGO
principle. In theory, this would allow us to use user-supplied websearch
strings (but see gotchas), even if they don't make much sense. Better
then nothing, right?

4. A small refactoring: I've replaced all WAIT* macros with a enum for
better debugging (names look much nicer in GDB). Hope this is
acceptable.

5. Finally, I've added a few more comments and tests. I haven't checked
the code coverage, though.

A few gotchas:

I haven't touched gettoken_tsvector() yet. As a result, the following
queries produce errors:

select websearch_to_tsquery('simple', '''');
ERROR: syntax error in tsquery: "'"

select websearch_to_tsquery('simple', '\');
ERROR: there is no escaped character: "\"

Maybe there's more. The question is: should we fix those, or it's fine
as it is? I don't have a strong opinion about this.

--
Dmitry Ivanov
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company

Attachment Content-Type Size
websearch_to_tsquery_v1.diff text/x-diff 28.1 KB

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