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I will be dynamically combining a range of tables with the exact same structure in RethinkDB.

I have my dynamically-generated list of tables in an array as follows:

tables = [r.table('table1'), r.table('table2'), ...]

And I am trying to do this:

r.union(r.args(tables))

But that just gives me an error: ReqlLogicError: Expected type DATUM but found TABLE

Overall, I have not been able to find a way to generate a list of tables in JavaScript and to add use r.union to combine them into a stream. Would appreciate help on this.

Thanks!

lyzazel
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2 Answers2

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You can use reduce to do what you want, we merge one by one, like r.table(t1).union(r.table(t2)).union(r.table(t3)).

Like this:

[r.table('t1'), r.table('t2'),  r.table('t3')].reduce(function(p, c) {
  return p.union(c)
})

Try it from data explorer.

kureikain
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0

The answer provided by kureikain works. I still wish the functionality existed in RethinkDB with r.args() (it seems to me that this would be consistent with the documentation of that function).

Moreover, one important tip tangentially related to this question: if you want to combine multiple tables into a stream through r.union() but be able to tell which table it is in the results, use merge(). So my query would look something like this:

[r.db('database').table('table1').merge({source: 'table1'}), r.db('database').table('table2').merge({source: 'table2'})].reduce(function(p, c) { return p.union(c) }).filter( ...)

This allows you to not only combine multiple tables into one stream, but to always distinguish between the source tables in your results (by looking up the value of the key 'source').

lyzazel
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