在Hologres中查詢慢Query日志，具體限制如下：

• 慢Query日志默認(rèn)保留一個(gè)月的數(shù)據(jù)，但是HoloWeb僅支持查最近7天的數(shù)據(jù)，如果需要查詢一個(gè)月內(nèi)的數(shù)據(jù)請(qǐng)使用SQL進(jìn)行查詢。

• 為了保證系統(tǒng)穩(wěn)定性，避免流量超載，單次查詢最多返回10000條慢Query日志。慢Query日志中的部分字段有長(zhǎng)度限制，詳情請(qǐng)參見query_log表字段說明。

• 慢Query日志屬于Hologres的元倉系統(tǒng)，慢Query日志查詢失敗不會(huì)影響實(shí)例中的業(yè)務(wù)Query運(yùn)行，故慢Query日志的穩(wěn)定性不在產(chǎn)品的SLA保護(hù)范圍內(nèi)。

Hologres的慢Query查詢?nèi)罩敬鎯?chǔ)于hologres.hg_query_log系統(tǒng)表中，其中：

• 在實(shí)例升級(jí)至V0.10版本后，將會(huì)默認(rèn)采集執(zhí)行時(shí)間大于100 ms的慢DML Query以及所有的DDL操作。

• 自V3.0.2版本開始，支持在原有的hologres.hg_query_log中，使用聚合方式記錄執(zhí)行時(shí)間小于100 ms的DML和查詢的記錄。

  • 系統(tǒng)會(huì)將執(zhí)行時(shí)間小于100 ms，成功且有指紋的Query（DQL和DML）操作進(jìn)行聚合記錄。

  • 聚合的主要列為：server_addr、usename、datname、warehouse_id、application_name、digest。

  • 每個(gè)連接每分鐘會(huì)匯總一次后上報(bào)。

hologres.hg_query_log系統(tǒng)表，包含的字段信息介紹如下。

您可以通過查詢hologres.hg_query_log表，獲取慢Query日志。如下將為您介紹進(jìn)行Query日志診斷常用的固定SQL語句。主要包括：

• 查詢query_log總查詢數(shù)

• 查詢每個(gè)用戶的慢Query情況

• 查詢某個(gè)慢Query的具體信息

• 查詢最近10分鐘消耗比較高的Query

• 查看最近3小時(shí)內(nèi)每小時(shí)的Query訪問量和數(shù)據(jù)讀取總量

• 查看與昨天同一時(shí)間對(duì)比過去3小時(shí)的數(shù)據(jù)訪問量情況

• 查詢最近10分鐘Query各階段耗時(shí)比較高的Query

• 查詢最先失敗的Query

• 查詢query_log總查詢數(shù)（默認(rèn)為近1個(gè)月內(nèi)的數(shù)據(jù)）。

  SELECT count(*) FROM hologres.hg_query_log;

  執(zhí)行結(jié)果如下，表示近1個(gè)月內(nèi)總共執(zhí)行了44個(gè)耗時(shí)大于指定閾值的Query。

  count
  -------
      44
  (1 row)

• 查詢每個(gè)用戶的慢Query個(gè)數(shù)。

  SELECT usename AS "用戶",
         count(1) as "Query個(gè)數(shù)"
  FROM hologres.hg_query_log
  GROUP BY usename
  order by count(1) desc;

  執(zhí)行結(jié)果如下，其中count(1)的單位是個(gè)數(shù)。

  用戶                   | Query個(gè)數(shù)
  -----------------------+-----
   1111111111111111      |  27
   2222222222222222      |  11
   3333333333333333      |   4
   4444444444444444      |   2
  (4 rows)

• 查詢某個(gè)慢Query的具體信息。

  SELECT * FROM hologres.hg_query_log WHERE query_id = '13001450118416xxxx';

  執(zhí)行結(jié)果如下，更多關(guān)于各參數(shù)的說明，請(qǐng)參見查看query_log表。

         usename      | status  |      query_id      | datname| command_tag | duration | message |      query_start       | query_date |                                             query                                                  | result_rows | result_bytes | read_rows |read_bytes | affected_rows | affected_bytes | memory_bytes | shuffle_bytes | cpu_time_ms | physical_reads |   pid   | application_name | engine_type |  client_addr  | table_write | table_read |   session_id   |     session_start      | command_id | optimization_cost | start_query_cost | get_next_cost | extended_cost | plan | statistics | visualization_info | query_detail | query_extinfo
  -----------------------+---------+--------------------+---------+-------------+----------+---------+------------------------+------------+---------------------------------------------------------------------------------------------------------+-------------+--------------+-----------+------------+---------------+----------------+--------------+---------------+-------------+----------------+---------+------------------+-------------+---------------+-------------+------------+-----------------+------------------------+------------+-------------------+------------------+---------------+---------------+------+------------+--------------------+--------------+---------------
   p4_11111111111xxxx | SUCCESS | 13001450118416xxxx | dbname | SELECT      |      149 |         | 2021-03-30 23:45:01+08 | 20210330   | explain analyze SELECT  * FROM tablename WHERE user_id = '20210330010xxxx' limit 1000;             |        1000 |       417172 |         0 |         0 |            -1 |             -1 |     26731376 |     476603616 |      321626 |              0 | 1984913 | psql             | {HQE}      | 33.41.xxx.xxx |             |            | 6063475a.1e4991 | 2021-03-30 23:44:26+08 | 0          |                58 |               22 |            67 |               |      |            |                    |              |
  (1 row)

• 查詢最近某個(gè)時(shí)間段（如10分鐘）消耗比較高的Query。您也可以根據(jù)業(yè)務(wù)需求修改具體時(shí)間，查詢目標(biāo)時(shí)間段消耗比較高的Query。

  SELECT status AS "狀態(tài)",
         duration AS "耗時(shí)(ms)",
         query_start AS "開始時(shí)間",
         (read_bytes/1048576)::text || ' MB' AS "讀取量",
         (memory_bytes/1048576)::text || ' MB' AS "內(nèi)存",
         (shuffle_bytes/1048576)::text || ' MB' AS "Shuffle",
         (cpu_time_ms/1000)::text || ' s' AS "CPU時(shí)間",
         physical_reads as "讀盤",
         query_id as "QueryID",
         query::char(30)
   FROM hologres.hg_query_log
   WHERE query_start >= now() - interval '10 min'
   ORDER BY duration DESC,
            read_bytes DESC,
            shuffle_bytes DESC,
            memory_bytes DESC,
            cpu_time_ms DESC,
            physical_reads DESC
  LIMIT 100;

  執(zhí)行結(jié)果如下：

  狀態(tài)     |耗時(shí)(ms) |    開始時(shí)間            | 讀取量 | 內(nèi)存  | Shuffle | CPU時(shí)間 | 讀盤 |      QueryID       |             query
  ---------+---------+------------------------+--------+-------+---------+---------+------+--------------------+--------------------------------
   SUCCESS |  149    | 2021-03-30 23:45:01+08 | 0 MB   | 25 MB | 454 MB  | 321 s   |    0 | 13001450118416xxxx | explain analyze SELECT  * FROM
   SUCCESS |  137    | 2021-03-30 23:49:18+08 | 247 MB | 21 MB | 213 MB  | 803 s   | 7771 | 13001491818416xxxx | explain analyze SELECT  * FROM
   FAILED  |   53    | 2021-03-30 23:48:43+08 | 0 MB   | 0 MB  | 0 MB    | 0 s     |    0 | 13001484318416xxxx | SELECT ds::bigint / 0 FROM pub
  (3 rows)

• 查看昨日新增的Query數(shù)量。

  • 統(tǒng)計(jì)昨日新增的Query總量。

    SELECT
        COUNT(1)
    FROM ( SELECT DISTINCT
            t1.digest
        FROM
            hologres.hg_query_log t1
        WHERE
            t1.query_start >= CURRENT_DATE - INTERVAL '1 day'
            AND t1.query_start < CURRENT_DATE
            AND NOT EXISTS (
                SELECT
                    1
                FROM
                    hologres.hg_query_log t2
                WHERE
                    t2.digest = t1.digest
                    AND t2.query_start < CURRENT_DATE - INTERVAL '1 day')
            AND digest IS NOT NULL
     ) AS a;

    執(zhí)行結(jié)果如下，表示昨日新增Query總量為10個(gè)。

    count  
    -------
        10 
    (1 row)

  • 按照查詢的類型（command_tag）分組統(tǒng)計(jì)昨日新增的Query數(shù)量。

    SELECT
        a.command_tag,
        COUNT(1)
    FROM ( SELECT DISTINCT
            t1.digest,
            t1.command_tag
        FROM
            hologres.hg_query_log t1
        WHERE
            t1.query_start >= CURRENT_DATE - INTERVAL '1 day'
            AND t1.query_start < CURRENT_DATE
            AND NOT EXISTS (
                SELECT
                    1
                FROM
                    hologres.hg_query_log t2
                WHERE
                    t2.digest = t1.digest
                    AND t2.query_start < CURRENT_DATE - INTERVAL '1 day')
                AND t1.digest IS NOT NULL) AS a
    GROUP BY
        1
    ORDER BY
        2 DESC;

    執(zhí)行結(jié)果如下，表示昨日新增8個(gè)INSERT和2個(gè)SELECT類型的Query。

    command_tag	| count  
    ------------+--------
    INSERT	    |    8   
    SELECT	    |    2
    (2 rows)

• 查看昨日新增的Query明細(xì)。

  SELECT
      a.usename,
      a.status,
      a.query_id,
      a.digest, 
      a.datname,
      a.command_tag,
      a.query,
      a.cpu_time_ms,
      a.memory_bytes
  FROM (
      SELECT DISTINCT
          t1.usename,
          t1.status,
          t1.query_id,
          t1.digest, 
          t1.datname,
          t1.command_tag,
          t1.query,
          t1.cpu_time_ms,
          t1.memory_bytes
      FROM
          hologres.hg_query_log t1
      WHERE
           t1.query_start >= CURRENT_DATE - INTERVAL '1 day' 
          AND t1.query_start < CURRENT_DATE 
          AND NOT EXISTS (
              SELECT
                  1
              FROM
                  hologres.hg_query_log t2
              WHERE
                  t2.digest = t1.digest
                  AND t2.query_start < CURRENT_DATE - INTERVAL '1 day'
          )
          AND t1.digest IS NOT NULL
  ) AS a; 

  執(zhí)行結(jié)果如下：

  usename	         |status  |query_id	           |digest	                            |datname|command_tag	|query	                            |cpu_time_ms   |memory_bytes
  -----------------+--------+--------------------+------------------------------------+-------+-------------+-----------------------------------+--------------+--------------
  111111111111xxxx |SUCCESS |100100425827776xxxx |md58cf93d91c36c6bc9998add971458ba1a |dbname	|INSERT	      |INSERT INTO xxx SELECT * FROM xxx  | 	   		 1748|	   898808596
  111111111111xxxx |SUCCESS |100100425827965xxxx |md5f7e87e2c9e0b3d9eddcd6b3bc7f04b3b |dbname	|INSERT       |INSERT INTO xxx SELECT * FROM xxx  | 	   		59891|	  6819529886
  111111111111xxxx |SUCCESS |100100425829654xxxx |md55612dc09d2d81074fd5deed1aa3eca9b |dbname	|INSERT	      |INSERT INTO xxx SELECT * FROM xxx  |   	   		  3|	     2100039
  111111111111xxxx |SUCCESS |100100425829664xxxx |md58d3bf67fbdf2247559bc916586d40011 |dbname	|INSERT	      |INSERT INTO xxx SELECT * FROM xxx  |     		10729|	  2052861937
  111111111111xxxx |SUCCESS |100100425830099xxxx |md503bd45d6b2d7701c2617d079b4d55a10 |dbname	|INSERT	      |INSERT INTO xxx SELECT * FROM xxx  |	   		   2196|     897948034
  111111111111xxxx |SUCCESS |100100425830186xxxx |md5c62169eaf3ea3a0c59bdc834a8141ac4 |dbname	|INSERT	      |INSERT INTO xxx SELECT * FROM xxx  |	   		   5268|    1734305972
  111111111111xxxx |SUCCESS |100100425830448xxxx |md59aa0c73b24c9c9eba0b34c8fdfc23bb0 |dbname	|INSERT	      |INSERT INTO xxx SELECT * FROM xxx  |	   		      2|       2098402
  111111111111xxxx |SUCCESS |100100425830459xxxx |md57d22c1d37b68984e9472f11a4c9fd04e |dbname	|INSERT	      |INSERT INTO xxx SELECT * FROM xxx  |	   		    113|      76201984
  111111111111xxxx |SUCCESS |100100525468694xxxx |md5ac7d6556fae123e9ea9527d8f1c94b1c |dbname	|SELECT	      |SELECT * FROM xxx limit 200	      |     		    6|	     1048576
  111111111111xxxx |SUCCESS |100101025538840xxxx |md547d09cdad4d5b5da74abaf08cba79ca0 |dbname	|SELECT	      |SELECT * FROM xxx limit 200	      |\N	           |\N        
  (10 rows)

• 查看昨日新增的Query趨勢(shì)（按小時(shí)展示）。

  SELECT
      to_char(a.query_start, 'HH24') AS query_start_hour,
      a.command_tag,
      COUNT(1)
  FROM (
      SELECT DISTINCT
          t1.query_start,
          t1.digest,
          t1.command_tag
      FROM
          hologres.hg_query_log t1
      WHERE
           t1.query_start >= CURRENT_DATE - INTERVAL '1 day' 
           AND t1.query_start < CURRENT_DATE 
           AND NOT EXISTS (
              SELECT
                  1
              FROM
                  hologres.hg_query_log t2
              WHERE
                  t2.digest = t1.digest
                  AND t2.query_start < CURRENT_DATE - INTERVAL '1 day'
           )
           AND t1.digest IS NOT NULL
  ) AS a 
  GROUP BY 1, 2
  ORDER BY 
  	3 DESC; 

  執(zhí)行結(jié)果如下，表示在昨日的11時(shí)、13時(shí)、21時(shí)分別新增了1個(gè)SELECT、1個(gè)SELECT、8個(gè)INSERT類型的Query。

  query_start_hour	|command_tag	|count
  ------------------+-------------+-----
  	            21	|INSERT	      |    8
  	            11	|SELECT	      |    1
  	            13	|SELECT	      |    1
  (3 rows)

• 歸類慢Query的次數(shù)。

  SELECT
      digest,
      command_tag,
      count(1)
  FROM
      hologres.hg_query_log
  WHERE
      query_start >= CURRENT_DATE - INTERVAL '1 day'
      AND query_start < CURRENT_DATE
  GROUP BY
      1,2
  ORDER BY
      3 DESC;

• 查詢過去1天CPU平均耗時(shí)前十的Query。

  SELECT
      digest,
      avg(cpu_time_ms)
  FROM
      hologres.hg_query_log
  WHERE
      query_start >= CURRENT_DATE - INTERVAL '1 day'
      AND query_start < CURRENT_DATE
      AND digest IS NOT NULL
      AND usename != 'system'
      AND cpu_time_ms IS NOT NULL
  GROUP BY
      1
  ORDER BY
      2 DESC
  LIMIT 10;

• 查看過去一周內(nèi)存（memory_bytes）平均消耗量前十的Query。

  SELECT
      digest,
      avg(memory_bytes)
  FROM
      hologres.hg_query_log
  WHERE
      query_start >= CURRENT_DATE - INTERVAL '7 day'
      AND query_start < CURRENT_DATE
      AND digest IS NOT NULL
      AND memory_bytes IS NOT NULL
  GROUP BY
      1
  ORDER BY
      2 DESC
  LIMIT 10;

• 查看最近3小時(shí)內(nèi)每小時(shí)的Query訪問量和數(shù)據(jù)讀取總量，用于對(duì)比判斷每個(gè)小時(shí)是否有數(shù)據(jù)量變化。

  SELECT
      date_trunc('hour', query_start) AS query_start,
      count(1) AS query_count,
      sum(read_bytes) AS read_bytes,
      sum(cpu_time_ms) AS cpu_time_ms
  FROM
      hologres.hg_query_log
  WHERE
      query_start >= now() - interval '3 h'
  GROUP BY 1;

• 查看與昨天同一時(shí)間對(duì)比過去3小時(shí)的數(shù)據(jù)訪問量情況，用于判斷相較于昨日是否有數(shù)據(jù)量訪問變化。

  SELECT
      query_date,
      count(1) AS query_count,
      sum(read_bytes) AS read_bytes,
      sum(cpu_time_ms) AS cpu_time_ms
  FROM
      hologres.hg_query_log
  WHERE
      query_start >= now() - interval '3 h'
  GROUP BY
      query_date
  UNION ALL
  SELECT
      query_date,
      count(1) AS query_count,
      sum(read_bytes) AS read_bytes,
      sum(cpu_time_ms) AS cpu_time_ms
  FROM
      hologres.hg_query_log
  WHERE
      query_start >= now() - interval '1d 3h'
      AND query_start <= now() - interval '1d'
  GROUP BY
      query_date;

• 查詢最近時(shí)間段（如最近10分鐘）Query各階段耗時(shí)比較高的Query。您也可以根據(jù)業(yè)務(wù)需求修改具體時(shí)間，查詢目標(biāo)時(shí)間段Query各階段耗時(shí)比較高的Query。

  SELECT
      status AS "狀態(tài)",
      duration AS "耗時(shí)(ms)",
      optimization_cost AS "優(yōu)化耗時(shí)(ms)",
      start_query_cost AS "啟動(dòng)耗時(shí)(ms)",
      get_next_cost AS "執(zhí)行耗時(shí)(ms)",
      duration - optimization_cost - start_query_cost - get_next_cost AS "其他耗時(shí)(ms)",
      query_id AS "QueryID",
      query::char(30)
  FROM
      hologres.hg_query_log
  WHERE
      query_start >= now() - interval '10 min'
  ORDER BY
      duration DESC,
      start_query_cost DESC,
      optimization_cost,
      get_next_cost DESC,
      duration - optimization_cost - start_query_cost - get_next_cost DESC
  LIMIT 100;

  執(zhí)行結(jié)果如下：

  狀態(tài)     | 耗時(shí)(ms) | 優(yōu)化耗時(shí)(ms) | 啟動(dòng)耗時(shí)(ms) | 執(zhí)行耗時(shí)(ms) | 其他耗時(shí)(ms) |      QueryID       |             query
  ---------+----------+--------------+--------------+--------------+--------------+--------------------+--------------------------------
   SUCCESS |     4572 |          521 |          320 |         3726 |            5 | 6000260625679xxxx  | -- /* user: wang ip: xxx.xx.x
   SUCCESS |     1490 |          538 |           98 |          846 |            8 | 12000250867886xxxx | -- /* user: lisa ip: xxx.xx.x
   SUCCESS |     1230 |          502 |           95 |          625 |            8 | 26000512070295xxxx | -- /* user: zhang ip: xxx.xx.
  (3 rows)

• 查詢最先失敗的Query。

  SELECT
      status AS "狀態(tài)",
      regexp_replace(message, '\n', ' ')::char(150) AS "報(bào)錯(cuò)信息",
      duration AS "耗時(shí)(ms)",
      query_start AS "開始時(shí)間",
      query_id AS "QueryID",
      query::char(100) AS "Query"
  FROM
      hologres.hg_query_log
  WHERE
      query_start BETWEEN '2021-03-25 17:00:00'::timestamptz AND '2021-03-25 17:42:00'::timestamptz + interval '2 min'
      AND status = 'FAILED'
  ORDER BY
      query_start ASC
  LIMIT 100;

  執(zhí)行結(jié)果如下：

  狀態(tài)    |                                                                     報(bào)錯(cuò)信息                                                                           | 耗時(shí)(ms)  |        開始時(shí)間        |     QueryID       | Query
  --------+--------------------------------------------------------------------------------------------------------------------------------------------------------+-------+------------------------+-------------------+-------
   FAILED | Query:[1070285448673xxxx] code: kActorInvokeError msg: "[holo_query_executor.cc:330 operator()] HGERR_code XX000 HGERR_msge internal error: status { c |  1460 | 2021-03-25 17:28:54+08 | 1070285448673xxxx | S...
   FAILED | Query:[1016285560553xxxx] code: kActorInvokeError msg: "[holo_query_executor.cc:330 operator()] HGERR_code XX000 HGERR_msge internal error: status { c |   131 | 2021-03-25 17:28:55+08 | 1016285560553xxxx | S...
  (2 rows)