Yet another parser?
Recently I needed to parse a fairly sophisticated search syntax for a project. I needed a pure XQuery solution, and MarkLogic's built-in search API wouldn't handle some of the syntax: nested groups, for example. So I wrote another one.
Here is a rough cut at the BNF
L ::= expr* expr ::= group | infixExpr | term group ::= prefixOp? '(' expr* ')' prefixOp ::= "+" | "-" | "~" | "NOT" infixExpr ::= (term | group) " " infixOp " " (term | group) infixOp ::= "*" | "OR" | "|" | "AND" | "ANDNOT" | "NOTIN" term ::= prefixOp? (field fieldOp)? (group | literal) field ::= (letter | "_")+ fieldOp ::= [":" | "=" | ">" | ">=" | "<" | "<=" | "!" | "!="] literal ::= (word | quoted_words) weight? quoted_words ::= '"' word (" " word)* '"' word ::= (letter | digit | "_")+ weight ::= ^digit+ number ::= digit+ letter ::= [A-Za-z] digit ::= [0-9]
XQYSP takes a slightly different approach than the Search API
or the older lib-parser.xqy, both of which returned cts:query items.
Instead, XQYSP returns an abstract syntax tree (AST) as XML.
It is up to you, the caller, to transform that AST into a cts:query.
That is a little more work for you,
but adds a lot of flexibility at the same time.
Most of the tasks that used to go into lib-parser-custom.xqy
can now be implemented without changing the parser itself.
To make it easier to get started, though,
there is some sample XQuery to generate a query from an AST in
and there is a test case in
query-eval.xqy code is provided as a simple example:
copy and modify it as needed for your application.
If the syntax isn't exactly what you need, this could make a nice template for your own search parser. Patches are also welcome.
The test cases use XQUT. If you find problems, please provide a test case.
Copyright (c) 2011-2014 Michael Blakeley. All Rights Reserved.
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