Update system variables for correctness

[morgo]

What is changed, added or deleted? (Required)

This updates the sysvars documentation for correctness (I used a script to generate it)

The main difference is that some new variables were not correctly in alphabetical order. I will comment on some of the other changes inline.

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• TomShawn
• dveeden

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[morgo]

This is actually wrong. In the source code you can see that it has a minValue of 0, and does not permit the special autovalue of -1:

https://github.com/pingcap/tidb/blob/22034c5bcd690dda3a9e794d6057cb5d9385d7cf/sessionctx/variable/sysvar.go#L876-L879

[TomShawn]

This was introduced in https://github.com/pingcap/docs-cn/pull/6875/files#diff-ec2cbb115cc58fe3afe2862eb5148732d323cbf7ae35dea97bd381a1f8d0e8a0R331. @hanfei1991 @LittleFall Could you help confirm whether the minimum value should be 0 or -1? Thanks!

[dveeden]

5.7.25-TiDB-v5.2.0-alpha-720-gd9bf3bf2d 127.0.0.1:4000   test  SQL  set session tidb_broadcast_join_threshold_count=-1;
ERROR: 1231 (42000): Variable 'tidb_broadcast_join_threshold_count' can't be set to the value of '-1'

[LittleFall]

Sorry to hear this. The reason for this error is that although we have implemented the corresponding logic, we have not expanded the scope of the variable, which results in behavior that is inconsistent with the document.
Thanks for pointing it out!
We will modify this document in pingcap/docs-cn#6926 to be consistent with the behavior, and fix this error in 5.2.1.

[morgo]

Same as above.

[TomShawn]

@LittleFall @hanfei1991 ditto

[morgo]

From pingcap/tidb#25743

[dveeden]

Is there something we can do in CI to avoid items from being out of order etc?

[dveeden]

Maybe something like this and/or run the script @morgo used?

[dvaneeden@dve-carbon docs]$ diff -u <(awk '/^#{3} / { print $2 }' system-variables.md) <(awk '/^#{3} / { print $2 }' system-variables.md | sort)
--- /dev/fd/63	2021-08-24 08:43:43.251885405 +0200
+++ /dev/fd/62	2021-08-24 08:43:43.252885414 +0200
@@ -1,7 +1,7 @@
 allow_auto_random_explicit_insert
+autocommit
 auto_increment_increment
 auto_increment_offset
-autocommit
 character_set_client
 character_set_connection
 character_set_database
@@ -9,8 +9,8 @@
 character_set_server
 cte_max_recursion_depth
 datadir
-default_authentication_plugin
 ddl_slow_threshold
+default_authentication_plugin
 foreign_key_checks
 hostname
 init_connect
@@ -87,9 +87,9 @@
 tidb_gc_run_interval
 tidb_gc_scan_lock_mode
 tidb_general_log
-tidb_hash_join_concurrency
 tidb_hashagg_final_concurrency
 tidb_hashagg_partial_concurrency
+tidb_hash_join_concurrency
 tidb_index_join_batch_size
 tidb_index_lookup_concurrency
 tidb_index_lookup_join_concurrency
@@ -100,19 +100,19 @@
 tidb_low_resolution_tso
 tidb_max_chunk_size
 tidb_max_delta_schema_count
+tidb_memory_usage_alarm_ratio
 tidb_mem_quota_apply_cache
 tidb_mem_quota_query
-tidb_memory_usage_alarm_ratio
 tidb_metric_query_range_duration
 tidb_metric_query_step
 tidb_multi_statement_mode
 tidb_opt_agg_push_down
-tidb_opt_limit_push_down_threshold
-tidb_opt_enable_correlation_adjustment
 tidb_opt_correlation_exp_factor
 tidb_opt_correlation_threshold
 tidb_opt_distinct_agg_push_down
+tidb_opt_enable_correlation_adjustment
 tidb_opt_insubq_to_join_and_agg
+tidb_opt_limit_push_down_threshold
 tidb_opt_prefer_range_scan
 tidb_opt_write_row_id
 tidb_partition_prune_mode

[morgo]

Maybe something like this and/or run the script @morgo used?

[dvaneeden@dve-carbon docs]$ diff -u <(awk '/^#{3} / { print $2 }' system-variables.md) <(awk '/^#{3} / { print $2 }' system-variables.md | sort)

The problem with the scripts is it requires the docs team has to be comfortable with maintaining them. My hope is that we can document everything and simplify the logic enough that #5720 can be used to auto-generate the docs. Until then, I will just contribute incremental updates to keep consistency.

[TomShawn]

LGTM

[TomShawn]

/merge

[ti-chi-bot]

This pull request has been accepted and is ready to merge.

Commit hash: dbb77f6

[ti-chi-bot]

In response to a cherrypick label: new pull request created: #6447.