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The existing implementation of the ltree ~ lquery match operator is sufficiently complex and undocumented that it's hard to tell exactly what it does. But one thing it clearly gets wrong is the combination of NOT symbols (!) and '*' symbols. A pattern such as '*.!foo.*' should, by any ordinary understanding of regular expression behavior, match any ltree that has at least one label that's not "foo". As best we can tell by experimentation, what it's actually matching is any ltree in which *no* label is "foo". That's surprising, and not at all what the documentation says. Now, that's arguably a useful behavior, so if we rewrite to fix the bug we should provide some other way to get it. To do so, add the ability to attach lquery quantifiers to non-'*' items as well as '*'s. Then the pattern '!foo{,}' expresses "any ltree in which no label is foo". For backwards compatibility, the default quantifier for non-'*' items has to be "{1}", although the default for '*' items is '{,}'. I wouldn't have done it like that in a green field, but it's not totally horrible. Armed with that, rewrite checkCond() from scratch. Treating '*' and non-'*' items alike makes it simpler, not more complicated, so that the function actually gets a lot shorter than it was. Filip Rembiałkowski, Tom Lane, Nikita Glukhov, per a very ancient bug report from M. Palm Discussion: https://postgr.es/m/CAP_rww=waX2Oo6q+MbMSiZ9ktdj6eaJj0cQzNu=Ry2cCDij5fw@mail.gmail.com |
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ltree.sql |