dolthub/dolt

Dolt differs from MySQL on allowing query global only system variable with session scope

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#6,722 opened on Sep 26, 2023

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bugcorrectnessgood first issuegood reprosql

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Description

Dolt display incorrect header for querying global only variable without specifying the scope. It also should error on querying global only variable with SESSION scope. Dolt:

mysql> SELECT @@system_time_zone;
+----------------------------+
| @@SESSION.system_time_zone |
+----------------------------+
| PDT                        |
+----------------------------+
1 row in set (0.00 sec)

mysql> SELECT @@SESSION.system_time_zone;
+----------------------------+
| @@SESSION.system_time_zone |
+----------------------------+
| PDT                        |
+----------------------------+
1 row in set (0.00 sec)

MySQL:

mysql> SELECT @@system_time_zone;
+--------------------+
| @@system_time_zone |
+--------------------+
| PDT                |
+--------------------+
1 row in set (0.00 sec)

mysql> SELECT @@SESSION.system_time_zone;
ERROR 1238 (HY000): Variable 'system_time_zone' is a GLOBAL variable

Contributor guide

Research direction
Investigate how Dolt handles system time zone when queried with SESSION scope vs no scope. Compare with MySQL's behavior and fix the header display and error generation.
Tech stack
go
Domain
backenddatabase
Issue type
Bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
2
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
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.
Clear
Prerequisites
SQLMySQL
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
70