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mu's query parser is the piece of software that turns your queries
into something the Xapian database can understand. So, if you query
"maildir:/inbox and subject:bla" this must be translated into a
Xapian::Query object which will retrieve the sought after messages.
Since mu's beginning, almost a decade ago, this parser was based on
Xapian's default Xapian::QueryParser. It works okay, but wasn't really
designed for the mu use-case, and had a bit of trouble with anything
that's not A..Z (think: spaces, special characters, unicode etc.).
Over the years, mu added quite a bit of pre-processing trickery to
deal with that. Still, there were corner cases and bugs that were
practically unfixable.
The solution to all of this is to have a custom query processor that
replaces Xapian's, and write it from the ground up to deal with the
special characters etc. I wrote one, as part of my "future, post-1.0
mu" reseach project, and I have now backported it to the mu 0.9.19.
From a technical perspective, this is a major cleanup, and allows us
to get rid of much of the fragile preprocessing both for indexing and
querying. From and end-user perspective this (hopefully) means that
many of the little parsing issues are gone, and it opens the way for
some new features.
From an end-user perspective:
- better support for special characters.
- regexp search! yes, you can now search for regular expressions, e.g.
subject:/h.ll?o/
will find subjects with hallo, hello, halo, philosophy, ...
As you can imagine, this can be a _heavy_ operation on the database,
and might take quite a bit longer than a normal query; but it can be
quite useful.
90 lines
2.1 KiB
C++
90 lines
2.1 KiB
C++
/*
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** Copyright (C) 2017 Dirk-Jan C. Binnema <djcb@djcbsoftware.nl>
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**
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** This library is free software; you can redistribute it and/or
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** modify it under the terms of the GNU Lesser General Public License
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** as published by the Free Software Foundation; either version 2.1
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** of the License, or (at your option) any later version.
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**
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** This library is distributed in the hope that it will be useful,
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** but WITHOUT ANY WARRANTY; without even the implied warranty of
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** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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** Lesser General Public License for more details.
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**
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** You should have received a copy of the GNU Lesser General Public
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** License along with this library; if not, write to the Free
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** Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA
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** 02110-1301, USA.
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*/
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#ifndef __PARSER_HH__
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#define __PARSER_HH__
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#include <string>
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#include <vector>
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#include <memory>
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#include <parser/data.hh>
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#include <parser/tree.hh>
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#include <parser/proc-iface.hh>
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// A simple recursive-descent parser for queries. Follows the Xapian syntax,
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// but better handles non-alphanum; also implements regexp
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namespace Mux {
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/**
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* A parser warning
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*
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*/
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struct Warning {
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size_t pos; /**< pos in string */
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const std::string msg; /**< warning message */
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/**
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* operator==
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*
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* @param rhs right-hand side
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*
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* @return true if rhs is equal to this; false otherwise
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*/
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bool operator==(const Warning& rhs) const {
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return pos == rhs.pos && msg == rhs.msg;
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}
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};
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/**
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* operator<<
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*
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* @param os an output stream
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* @param w a warning
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*
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* @return the updated output stream
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*/
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inline std::ostream&
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operator<< (std::ostream& os, const Warning& w)
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{
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os << w.pos << ":" << w.msg;
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return os;
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}
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/**
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* Parse a query string
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*
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* @param query a query string
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* @param warnings vec to receive warnings
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* @param proc a Processor object
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*
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* @return a parse-tree
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*/
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using WarningVec=std::vector<Warning>;
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using ProcPtr = const std::unique_ptr<ProcIface>&;
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Tree parse (const std::string& query, WarningVec& warnings,
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ProcPtr proc = std::make_unique<DummyProc>());
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} // namespace Mux
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#endif /* __PARSER_HH__ */
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