如何判断查询在 QuestDB 中以多线程运行？

Question

我正在 QuestDB 中运行以下查询：

SELECT 
    timestamp,
    first(price) AS open,
    last(price) AS close,
    min(price),
    max(price),
    sum(amount) AS volume
FROM trades
WHERE symbol = 'BTC-USD' AND timestamp > dateadd('d', -1, now())
SAMPLE BY 15m ALIGN TO CALENDAR;

如何判断此查询使用了服务器上的所有可用核心？

Answer 1

您应该检查查询的执行计划。您可以通过在查询文本的开头添加 EXPLAIN 子句来查看它：

EXPLAIN SELECT 
    timestamp,
    first(price) AS open,
    last(price) AS close,
    min(price),
    max(price),
    sum(amount) AS volume
FROM trades
WHERE symbol = 'BTC-USD' AND timestamp > dateadd('d', -1, now())
SAMPLE BY 15m ALIGN TO CALENDAR;

如果您在输出中看到

Async ...

节点，例如

Async JIT Group By

或

Async JIT Filter

，表示查询执行计划的相应部分并行运行，即在多个线程上运行。