taosdata/TDengine

查询时会出现耗时很长的问题

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#34,011 opened on Dec 22, 2025

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Description

sql语句：select last(ts) as ts, last(value) as val from test_260 where ts >= '2025-08-01 00:00:00' and ts <= '2025-08-31 23:59:59' INTERVAL (1d) SLIDING (1d) FILL(prev); test_260是子表，一个月内数据量大于50w条，快时几百ms就出结果，慢时会出现60s以上，查询的时候可能有服务在往时序库写数据，也观察过cpu和内存占用百分比不是很多。测试环境也模拟这样的数据量，测试不同表的查询一直无法复现超时的问题。目前不清楚怎么分析出现这种情况的具体原因，是否有其他工具或者命令分析出在查询这种sql语句时，数据交换或者其他原因的

Contributor guide

Research direction
Analyze the query plan using EXPLAIN, monitor system resources during slow queries, check for lock contention, and consider using profiling tools like perf or strace to trace the handler.
Tech stack
csql
Domain
backenddatabaseperformance
Issue type
Bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
4
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
3-5 days
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Needs investigation
Prerequisites
SQLDatabase BasicsProfiling
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
25