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show tables get wrong result after restart tidb and a snapshot read #55835

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tiancaiamao opened this issue Sep 4, 2024 · 1 comment · Fixed by #55856
Closed

show tables get wrong result after restart tidb and a snapshot read #55835

tiancaiamao opened this issue Sep 4, 2024 · 1 comment · Fixed by #55856
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feature/developing the related feature is in development severity/moderate sig/sql-infra SIG: SQL Infra type/bug The issue is confirmed as a bug.

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@tiancaiamao
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Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

  1. use infoschema v2
set @@global.tidb_schema_cache_size = '512MB';
  1. create table t and drop it, record the timestamp when t is available
use test;
create table t (id int);
select now();  ## get  '2024-09-04 09:48:54'
drop table t;

  1. restart tidb

  2. after a snapshot read, show tables goes wrong.

mysql> show tables;
Empty set (0.00 sec)

mysql> select * from t as of timestamp '2024-09-04 09:48:54';
Empty set (0.00 sec)

mysql> show tables;
+----------------+
| Tables_in_test |
+----------------+
| t              |
+----------------+
1 row in set (0.00 sec)

2. What did you expect to see? (Required)

mysql> show tables;
Empty set (0.00 sec)

mysql> show full tables;
Empty set (0.00 sec)

mysql> select * from information_schema.tables where table_schema = 't';
Empty set (0.00 sec)

3. What did you see instead (Required)

mysql> show tables;
+----------------+
| Tables_in_test |
+----------------+
| t              |
+----------------+
1 row in set (0.00 sec)

mysql> show full tables;
Empty set (0.00 sec)

mysql> select * from information_schema.tables where table_schema = 't';
Empty set (0.00 sec)

4. What is your TiDB version? (Required)

master
@tiancaiamao tiancaiamao added type/bug The issue is confirmed as a bug. severity/moderate feature/developing the related feature is in development labels Sep 4, 2024
@tiancaiamao
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This issue is similiar to #54926

After create and drop table, the infoschema history should be:

version 54:  t
version 55:  t = tomb

Then reading latest infoschema get the tomb and we know there are no tables.

When we restart tidb, we have no infoschema versions history.

no versions

After a snapshot read, the snapshot infoschema is inserted:

version 54: t

Now things go wrong, we do not have a tomb of version 55, so we mistakenly read the t.

@tiancaiamao tiancaiamao mentioned this issue Sep 4, 2024
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@jebter jebter added the sig/sql-infra SIG: SQL Infra label Sep 6, 2024
ti-chi-bot bot pushed a commit that referenced this issue Sep 11, 2024
@tiancaiamao
domain,infoschema: fix 'show tables' after snapshot read (#55856)
ae8f977 
close #55835
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feature/developing the related feature is in development severity/moderate sig/sql-infra SIG: SQL Infra type/bug The issue is confirmed as a bug.
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domain,infoschema: fix 'show tables' after snapshot read tiancaiamao/tidb
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