config: update the default value of feedback-probability (pingcap#5784) (pingcap#5786)

Author: ti-chi-bot

statistics.md

@@ -147,11 +147,7 @@ Three system variables related to automatic update of statistics are as follows:
 
 When the ratio of the number of modified rows to the total number of rows of `tbl` in a table is greater than `tidb_auto_analyze_ratio`, and the current time is between `tidb_auto_analyze_start_time` and `tidb_auto_analyze_end_time`, TiDB executes the `ANALYZE TABLE tbl` statement in the background to automatically update the statistics of this table.
 
-When the query is executed, TiDB collects feedback with the probability of `feedback-probability` and uses it to update the histogram and Count-Min Sketch. You can modify the value of `feedback-probability` in the configuration file. The default value is `0.05`. You can set the value to `0.0` to disable this feature.
-
-> **Note:**
->
-> If you set the value of `feedback-probability` to `0` in the configuration file, a failure will occur and an error will be reported. To disable `feedback-probability`, you need to set the value to `0.0`.
+Before v5.0, when the query is executed, TiDB collects feedback with the probability of `feedback-probability` and uses it to update the histogram and Count-Min Sketch. **In v5.0, this feature is disabled by default, and it is not recommended to enable this feature.**
 
 ### Control `ANALYZE` concurrency
 

tidb-configuration-file.md

@@ -400,8 +400,8 @@ Configuration items related to performance.
 ### `feedback-probability`
 
 - The probability that TiDB collects the feedback statistics of each query.
-- Default value: `0.05`
-- TiDB collects the feedback of each query at the probability of `feedback-probability`, to update statistics.
+- Default value: `0`
+- This feature is disabled by default, and it is not recommended to enable this feature. If it is enabled, TiDB collects the feedback of each query at the probability of `feedback-probability`, to update statistics.
 
 ### `query-feedback-limit`