since we cannot do stats derive and cost estimate on agg very good.
this PR remove some aggregate pattern that usually not good.
1. one stage agg after exchange. this pattern is good only when process very few rows.
2. three stage distinct agg with gather middle merge.
For each release of Doris, there are some experimental features.
These feature may not stable or qualified enough, and user need to use it by setting config or session variables,
eg, set enable_mtmv = true, otherwise, these feature is disable by default.
We should explicitly tell user which features are experimental, so that user will notice that and decide whether to
use it.
Changes
In this PR, I support the experimental_ prefix for FE config and session variables.
Session Variable
Given enable_nereids_planner as an example.
The Nereids planner is an experimental feature in Doris, so there is an EXPERIMENTAL annotation for it:
@VariableMgr.VarAttr(..., expType = ExperimentalType.EXPERIMENTAL)
private boolean enableNereidsPlanner = false;
And for compatibility, user can set it by:
set enable_nereids_planner = true;
set experimental_enable_nereids_planner = true;
And for show variables, it will only show experimental_enable_nereids_planner entry.
And you can also see all experimental session variables by:
show variables like "%experimental%"
Config
Same as session variable, give enable_mtmv as an example.
@ConfField(..., expType = ExperimentalType.EXPERIMENTAL)
public static boolean enable_mtmv = false;
User can set it in fe.conf or ADMIN SET FRONTEND CONFIG stmt with both names:
enable_mtmv
experimental_enable_mtmv
And user can see all experimental FE configs by:
ADMIN SHOW FRONTEND CONFIG LIKE "%experimental%";
TODO
Support this feature for BE config
Only add experimental for:
enable_pipeline_engine
enable_nereids_planner
enable_single_replica_insert
and FE config:
enable_mtmv
enabel_ssl
enable_fqdn_mode
Should modify other config and session vars
turn on all test case in scalar function W except width_bucket(fix be bug in next PR)
turn off all test case for group_concat(distinct order by)
fix return nullable in TimestampArithmetic
