@Override
    public CompiledCondition compileCondition(Expression condition, MatchingMetaInfoHolder matchingMetaInfoHolder,
                                              List<VariableExpressionExecutor> variableExpressionExecutors,
                                              Map<String, Table> tableMap, WindowState state,
                                              SiddhiQueryContext siddhiQueryContext) {
        return OperatorParser.constructOperator(state.expiredEventChunk, condition, matchingMetaInfoHolder,
                variableExpressionExecutors, tableMap, siddhiQueryContext);
    }
Here an assumption is taken:
Parameter: timestamp: The time which the window determines as current time and will act upon,
the value of this parameter should be monotonically increasing.
from https://docs.wso2.com/display/CEP400/Inbuilt+Windows#InbuiltWindows-externalTime
modules/siddhi-core/src/main/java/io/siddhi/core/query/processor/stream/window/ExternalTimeBatchWindowProcessor.java