Redundant slow queries

[cyliu0]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. What did you do? If possible, provide a recipe for reproducing the error.
   dumpling from tables

2. What did you expect to see?
   No redundant queries

3. What did you see instead?
   The first and the last one are the same queries.

# Time: 2021-06-21T15:03:57.452601441+08:00
# Txn_start_ts: 425786725567299588
# User@Host: root[root] @ 127.0.0.1 [127.0.0.1]
# Conn_ID: 2785
# Query_time: 0.591801165
# Parse_time: 0.000073645
# Compile_time: 0.000423339
# Rewrite_time: 0.000087014
# Optimize_time: 0.000222869
# Wait_TS: 0
# Is_internal: false
# Digest: 071022814ccc7066779c13751314ec2c061ee43d9d5ebfe42d67875885a44146
# Num_cop_tasks: 0
# Mem_max: 903096
# Prepared: false
# Plan_from_cache: false
# Plan_from_binding: false
# Has_more_results: false
# KV_total: 0
# PD_total: 0
# Backoff_total: 0
# Write_sql_response_total: 0.000002037
# Succ: true
# Plan: tidb_decode_plan('vgJYMAkzXzYJMAk4MDAwCUNvbHVtbiM0LCANCmQxOAkzCXRpbWU6NTkxLjFtcywgbG9vcHM6MgEjdG5jdXJyZW5jeTo1CTYzLjAgS0IJTi9BCjEJMTRfNzpVAAA1HUodSBAJMTEuNAE5MDAgQnl0ZXMKMgkxXzkRPAhlcSgNiiwyLCAiY29tcyIpLCAZFlgzLCAiUEtfTVVMVElfQ09MXzY3NjUiKRlrCDAuOS5tABA4MDcuNQFuPE
4vQQozCTExXzEwCTAJMTAB/lB0YWJsZTpDT0xVTU5TCTExODg5NgkJ/QQ3NhlGLDExOAlOL0EJTi9BCg==')
# Plan_digest: 30505f4b0bbdb39a59b837d7b4ce091c522723b0b6efa4e566cfe8769f5d939c
SELECT COLUMN_NAME,EXTRA FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_SCHEMA='coms' AND TABLE_NAME='PK_MULTI_COL_6765' ORDER BY ORDINAL_POSITION;
# Time: 2021-06-21T15:03:57.835300364+08:00
# Txn_start_ts: 425786725567299588
# User@Host: root[root] @ 127.0.0.1 [127.0.0.1]
# Conn_ID: 2785
# Query_time: 0.380146959
# Parse_time: 0.000041277
# Compile_time: 0.000238671
# Rewrite_time: 0.000069852
# Optimize_time: 0.000096307
# Wait_TS: 0
# Is_internal: false
# Digest: 94c6ba74557f97f611beb2b6dd595f9e6b93a372b62ebcc59158798b9707d757
# Num_cop_tasks: 0
# Mem_max: 414244
# Prepared: false
# Plan_from_cache: false
# Plan_from_binding: false
# Has_more_results: false
# KV_total: 0
# PD_total: 0
# Backoff_total: 0
# Write_sql_response_total: 0.00000163
# Succ: true
# Plan: tidb_decode_plan('9AHwTzAJM180CTAJODAwMAlDb2x1bW4jOQkxCXRpbWU6Mzc5LjdtcywgbG9vcHM6MiwgQ29uY3VycmVuY3k6NQk1OS4yIEtCCU4vQQoxCTFfNQkwCUkIZXEoDUwsMiwgImNvbXMiKSwgGRZgMywgIlBLX01VTFRJX0NPTF82NzY1IikJMRl4BDZtGXgUCTM0NS40EWooMgkxMV82CTAJMTABtUR0YWJsZTpUQUJMRVMJMjkyMzERRQg1LjIZRSgzMQlOL0EJTi9BCg==')
# Plan_digest: c812fd56edc7a7c7053f1ec10511ddc9db6f33a472d4525280d177fb4d6f4930
select AVG_ROW_LENGTH from INFORMATION_SCHEMA.TABLES where table_schema='coms' and table_name='PK_MULTI_COL_6765';
# Time: 2021-06-21T15:03:58.510696292+08:00
# Txn_start_ts: 425786725567299588
# User@Host: root[root] @ 127.0.0.1 [127.0.0.1]
# Conn_ID: 2785
# Query_time: 0.673026906
# Parse_time: 0.000057562
# Compile_time: 0.00031538
# Rewrite_time: 0.00007342
# Optimize_time: 0.000148629
# Wait_TS: 0
# Is_internal: false
# Digest: 071022814ccc7066779c13751314ec2c061ee43d9d5ebfe42d67875885a44146
# Num_cop_tasks: 0
# Mem_max: 903096
# Prepared: false
# Plan_from_cache: false
# Plan_from_binding: false
# Has_more_results: false
# KV_total: 0
# PD_total: 0
# Backoff_total: 0
# Write_sql_response_total: 0.000002211
# Succ: true
# Plan: tidb_decode_plan('wgJYMAkzXzYJMAk4MDAwCUNvbHVtbiM0LCANCmQxOAkzCXRpbWU6NjcyLjRtcywgbG9vcHM6MgEjdG5jdXJyZW5jeTo1CTYzLjAgS0IJTi9BCjEJMTRfNzpVAAA1LkoAADMdShAJMTEuNAE7MDAgQnl0ZXMKMgkxXzkRPghlcSgNjCwyLCAiY29tcyIpLCAZFlgzLCAiUEtfTVVMVElfQ09MXzY3NjUiKS5tAAAyLm0AEDgwNy41AW
48Ti9BCjMJMTFfMTAJMAkxMCEAUHRhYmxlOkNPTFVNTlMJMTE4ODk2CQn/DDU2LjgZSCwxMTgJTi9BCU4vQQo=')
# Plan_digest: 30505f4b0bbdb39a59b837d7b4ce091c522723b0b6efa4e566cfe8769f5d939c
SELECT COLUMN_NAME,EXTRA FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_SCHEMA='coms' AND TABLE_NAME='PK_MULTI_COL_6765' ORDER BY ORDINAL_POSITION;

4. Versions of the cluster

   • Dumpling version (run dumpling -V):

     Release version: v5.1.0
     Git commit hash: 292cbe6c9da0f53a262332d7711dd6ba96567411
     Git branch:      heads/refs/tags/v5.1.0
     Build timestamp: 2021-06-18 01:49:31Z
     Go version:      go version go1.16.4 linux/amd64
     

   • Source database version (execute SELECT version(); in a MySQL client):

     (paste source database version here)
     

   • Other interesting information (system version, hardware config, etc):

5. Operation logs

   • Please upload dumpling.log for Dumpling if possible
   • Other interesting logs

6. Configuration of the cluster and the task

   • running command for Dumpling if possible

[cyliu0]

/severity moderate