Query syntax for searching (multiple) nil values

[tomas]

Hi, me again. :)

I'm able to perform using two or more filters where one of them is blank/nil, for example:

table.select("+name:foo +description:\\").first # matches name: foo', description: nil

This works as long as the nil column is at the end of the list, because if I do:

table.select("+description:\\ +name:foo").first

I get a nasty column lookup failed error.

So the question is: how can I make the second example work?

This is important because I want to be able to search for two nil columns at the same time, and this problem is preventing me from doing so.

Hope you can help me out. Thanks!

[kou]

How about the following?

table.select do |record|
  conditions = []
  conditions << (record.name =~ name) if name
  conditions << (record.description =~ description) if description
  conditions
end

[tomas]

Thanks, but I need to make it work using the query syntax (not the block syntax). This is because I want to combine different criteria dynamically.

If not possible, can this be fixed in a future version of rroonga?

[kou]

You can use the query syntax with record.name.match(name).

[tomas]

Sorry, I meant the table.select("+column:value") syntax, as shown in the first message. Not sure how it's called.

[kou]

How do you create the query syntax? End users specify it? Or your program builds it?

[tomas]

I'm building an ORM around Groonga (rroonga) so that different apps can declare their models in an ActiveRecord-like fashion (using relationships, named scopes, etc).

I'm currently using this ORM in a specific app where I need to run a query to find records with nil values for two columns.

[kou]

Ah, sorry. I misunderstood.

The following will work:

table.select do |record|
  conditions = []
  conditions << (record.name == name.to_s)
  conditions << (record.description == description.to_s)
  conditions
end

I think that you can use the above API in your ORM. (I'm not sure why you need the query syntax with ORM.)

[tomas]

Using the block syntax would make implementation much more complex, so I'd rather keep on using the query/string syntax (I've managed to do everything else so far).

Where would I modify this in the rroonga source code? Either to submit a PR or to start my own fork of this project.

Thanks again

[kou]

I don't know why the block syntax causes more complex implementation but does table.select("+description:\"\" +name:foo") work for you?

[tomas]

Forgot to say that the \"\" thing worked. :)

Thanks!