Aerospike: get a set of keys from LDT Bin in one call
Let's assume I have the following values in my LDT bucket (LargeMap):
key1, value1 key2, value2 key3, value3 key4, value4 . . key50, value50
Now I am getting my data using the following snippet:
Map<?, ?> myFinalRecord = new HashMap<?, ?>();
// First call to client to get the largeMap associated with the bin
LargeMap largeMap = myDemoClient.getLargeMap(myPolicy, myKey, myLDTBinName, null);
for (String myLDTKey : myRequiredKeysFromLDTBin) {
try {
// Here each get call results in one call to aerospike
myFinalRecord.putAll(largeMap.get(Value.get(myLDTKey)));
} catch (Exception e) {
log.warn("Key does not exist in LDT Bin");
}
}
The problem is here if it myRequiredKeysFromLDTBin
contains 20 keys. Then he largeMap.get(Value.get(myLDTKey))
will make 20 aerospace calls.
So if I take 1ms lookup time per transaction , here my one call to retrieve 20 IDs from a record would result in 20 aerospace calls. This will increase the response time by approx. 20 ms !
So, is there a way that I can just pass a set of IDs to be fetched from the LDT tray and it only requires one call?
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There is no direct API for multi-get. One way to do this would be the API to call lmap directly from the server via UDF.
Example 'mymap.lua'
local lmap = require('ldt/lib_lmap');
function getmany(rec, binname, keys)
local resultmap = map()
local keycount = #keys
for i = 1,keycount,1 do
local rc = lmap.exists(rec, binname, keys[i])
if (rc == 1) then
resultmap[keys[i]] = lmap.get(rec, binname, keys[i]);
else
resultmap[keys[i]] = nil;
end
end
return resultmap;
end
Register this lua file
aql> register module 'mymap.lua'
OK, 1 module added.
aql> execute lmap.put('bin', 'c', 'd') on test.demo where PK='1'
+-----+
| put |
+-----+
| 0 |
+-----+
1 row in set (0.000 secs)
aql> execute lmap.put('bin', 'b', 'c') on test.demo where PK='1'
+-----+
| put |
+-----+
| 0 |
+-----+
1 row in set (0.001 secs)
aql> execute mymap.getmany('bin', 'JSON["b","a"]') on test.demo where PK='1'
+--------------------------+
| getmany |
+--------------------------+
| {"a":NIL, "b":{"b":"c"}} |
+--------------------------+
1 row in set (0.000 secs)
aql> execute mymap.getmany('bin', 'JSON["b","c"]') on test.demo where PK='1'
+--------------------------------+
| getmany |
+--------------------------------+
| {"b":{"b":"c"}, "c":{"c":"d"}} |
+--------------------------------+
1 row in set (0.000 secs)
Java code to call this would be
try {
resultmap = myClient.execute(myPolicy, myKey, 'mymap', 'getmany', Value.get(myLDTBinName), Value.getAsList(myRequiredKeysFromLDTBin)
} catch (Exception e) {
log.warn("One of the key does not exist in LDT bin");
}
The value will be set if the key exists, and it will return NIL if not.
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