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Redis – Lua script converts empty array to object

Lua script converts empty array as an object. How to avoid conversion.

test.lua

local json_str = '{"items":[],"properties":{}}'
return cjson.encode(cjson.decode(json_str))

Output

redis-cli --eval test.lua

“{“items”:{},”properties”:{}}”

items are an array [] but the output is an object {}

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2

Answers


  1. 0

    The main difference between JSON object definition and lua table, that lua table has no type array.

    Empty JSON array [] or object {} is converted to lua table {}, but empty lua table {} can be converted to array [] or object {}.

    To my knowledge, cjson for redis has no solution for this problem at the moment, possible solution is mentioned in Redis Lua Differetiating empty array and object. (I can’t argue if it works)

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  2. 0

    According to this great post you can set the following option to cjson:

    cjson.encode_empty_table_as_object(false)

    So cjson.encode({dogs = {}}) resolves to {"dogs": []}

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