I'm building a class that will iterate across a range of databases and
perform the same query on each one. The queries return an array of numbers
that will get passed on for statistical analysis. I want to pass in the
names of the databases, the table, and the query to perform in the class
constructor.
The meat of the class would look like
database_names.each.with_index do |database_name, idx|
db = Sequel.connect(database_name)
result[idx] = db[<:table>].<query>
db.close
end
Passing in the database names and symbol for the table is easy enough.
Passing in the query is tricky.
I've been working with .send() and making good progress. For example:
table = :my_table
query = [:select, :NodeId]
db[table].send(*query)
=> #<Sequel::SQLite::Dataset: "SELECT `NodeId` FROM `my_table`
But I not getting anywhere with where clauses.
query = [[:select, :NodeId], [:where, :Timestamp, :"=>", :"60"]]
db[table].send(*query[0]).send(*query[1]) # Obviously automate the
unrolling of a variable-length query
=> #<Sequel::SQLite::Dataset: "SELECT `NodeId` FROM `my_table` WHERE
(`Timestamp` AND `=>` AND `60`)">
How can I get that where clause to evaluate to "WHERE ('Timestamp' = 60)"?
I'm not an experienced Ruby coder and am clearly missing some nuances of
the language when it comes to send() and treatment of symbols...
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