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karrtojal
karrtojal

Reputation: 886

Implement a LIKE query operator for Aerospike

I'm new with Aerospike. Is there any easy way to make a search with a part of text like Mysql. Example:

select * from test where column like '%hello%';

I find difficult to migrate to a NoSQL database if this common operations are not supported. Thanks.

Upvotes: 4

Views: 1806

Answers (1)

Ronen Botzer
Ronen Botzer

Reputation: 7117

Predicate filtering was added in release 3.12. You can use the stringRegex method of the PredExp class of the Java client to implement an equivalent to LIKE. Predicate filters also currently exists for the C, C# and Go clients.

This example in the Aerospike Java client shows something similar:

    Statement stmt = new Statement();
    stmt.setNamespace(params.namespace);
    stmt.setSetName(params.set);        
    stmt.setFilter(Filter.range(binName, begin, end));
    stmt.setPredExp(
        PredExp.stringBin("bin3"),
        PredExp.stringValue("prefix.*suffix"),
        PredExp.stringRegex(RegexFlag.ICASE | RegexFlag.NEWLINE)
        );

If you're using a language client that doesn't yet support predicate filtering, you'd implement this with a stream UDF attached to a scan or query. For example, in the Python client you would create an instance of class aerospike.Query with or without a predicate and call the aerospike.Query.apply() method.

Ideally you would accelerate this by bucketing and using a predicate to narrow down your search, rather than scanning the entire set. For example, you can create a startswith bin that holds the first letter, use the predicate to find that, then send the records matched through the stream UDF. Just note that a LIKE is a horribly slow operation on an RDBMS, as well, because it can't use an index.

local function bin_like(bin, val, plain)
    return function(rec)
        if rec[bin] and type(rec[bin]) == "string" then
            if string.find(rec[bin], val, 1, plain) then
                return true
            else
                return false
        else
            return false
        end
    end
end

local function map_record(rec)
  local ret = map()
  for i, bin_name in ipairs(record.bin_names(rec)) do
    ret[bin_name] = rec[bin_name]
  end
  return ret
end

function check_bins_match(stream, bin, val, plain)
  return stream : filter(bin_like(bin, val, plain)) : map(map_record)
end

Upvotes: 3

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