Aerospike limiting records by lexicographic order - aerospike

Question

Can Aerospike get records by lexicographic order.For example if U want all the records that start with "a" then U like to search for bin >="a" AND bin <="az"

Answer 1

aerospike support UDF modules(in LUA and C language) https://www.aerospike.com/docs/udf/developing_lua_modules.html
which can serve your purpose.

Answer 2

User-Defined Functions written in Lua extend the core functionality of Aerospike. You would create a stream UDF and attach it to a query.
One best practice for stream UDFs in Aerospike is to eliminate as many records as possible before passing the results into the UDF, so in this case I would create another bin to hold a prefix (first letter, or a substring, depending on your use case) and build a secondary index on it. The idea is that the query portion should return as small of a subset as you can reliably. For your example the prefix can be a single character, you can add a new bin 'firstchar' to the records in the set, then build a secondary index on it.
The stream UDF module would look something like:
local function range_filter(bin_name, substr_from, substr_to)
return function(record)
local val = record[bin_name]
if type(val) ~= 'string' then
return false
end
if val >= substr_from and val <= substr_to then
return true
else
return false
end
end
end
local function rec_to_map(record)
local xrec = map()
for i, bin_name in ipairs(record.bin_names(record)) do
xrec[bin_name] = xrec[bin_name]
end
return xrec
end
function str_between(stream, bin_name, substr_from, substr_to)
return stream : filter(range_filter(bin_name, substr_from, substr_to)) : map(rec_to_map)
end
In the Python client you'd invoke it as follows:
import aerospike
from aerospike import predicates as p
# instantiate the client and connect to the cluster, then:
query = client.query('test', 'this')
query.where(p.equals('firstchar', 'a'))
query.apply('strrangemod', 'str_between', ['a','az'])