java-Aerospike：在一个调用中从LDT Bin中检索一组密钥

假设在我的LDT(LargeMap)Bin中,我具有以下值,

key1, value1   
key2, value2   
key3, value3   
key4, value4   
. .   
key50, value50

现在,我使用以下代码段获取所需的数据：

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");
    }
}

如果myRequiredKeysFromLDTBin包含20个密钥,那么问题就出在这里.然后largeMap.get(Value.get(myLDTKey))将对Aerospike进行20次调用.

因此,如果我每笔事务的检索时间为1毫秒,那么我从记录中检索20个ID的一次调用将导致对Aerospike的20次调用.这将使我的响应时间增加到大约. 20毫秒！

那么,有什么方法可以让我传递一组要从LDT Bin中检索的ID,而只需要一个调用就可以了？

解决方法:

没有直接的API可以进行多重获取.一种方法是直接通过UDF从服务器多次调用lmap API.

示例“ 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

注册这个lua文件

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代码来调用这个

 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");
 }

如果键存在,则将设置值；如果不存在,则将返回NIL.

标签：aerospike,java
来源： https://codeday.me/bug/20191028/1955739.html