Help using list in UDF



I’m trying to maintain a list of strings.

This is my code when I create a record:

local function initRecord(record)
    if(not aerospike:exists(record)) then
        record.backlog = list()
        for i=1,3, 1 do
            local val = 'n/a'
            record.backlog[i] = val
        local rc = 0;
        rc = aerospike:create(record)
        if( rc == nil or record == nil ) then
            error("Could not create record")

And it works fine (bins:(backlog:[n/a, n/a, n/a]), but when I want to modify this list, it does not seam to do anything with any of the following methods:

local function pushToBacklog(record, requestId)
    list.append(record.backlog, requestId)


local function pushToBacklog(record, requestId)
    record.backlog[1] = requestId

Any idea?



Try adding the following code just before you call aerospike:update(…)

record.backlog = record.backlog

It seems a bit strange, but I’ll explain. To Lua, the Aerospike record “looks” like a table, and you can operate on it like you would a table; cstivers78 did a great job on implementing this.

Here is the secret: For Aerospike to know that the bin needs to be updated, the bin needs to be “touched”. You are adding to a list in the UDF, which is OK, but the Bin containing a pointer to the list has not been modified, or “touched”. So assigning the bin to itself should work.




Thanks! This works fine now.


Hi Peter, sorry for reviving this thread. For improvement of DX, wouldn’t it be possible that all cdt-list write ops automatically touch the bin / mark it as dirty? It’s quite counter-intuitive to lua beginners and can potentially cost developers hours to debug with the few examples available (none explaining the need for local bincopy = rec.binname).

With the new cdt list ops, it’s also unclear if that trick does a complete copy of the list instead of operating just on the elements changed (especially for in-memory namespace) - which would degrade performance a lot (though not a priority IMHO)! When benchmarking in-memory vs. ssd namespace (record udf using cdt list ops), I saw virtually no difference which I’d interpret as it’s actually doing a clone or the record lock starts throttling at 6000 record-udf apply’s/second.

Never saw the need for this with any other program using lua, too.

Cheers, Manuel