From 2ec1371407a20ecbf404bb9bf8aa3ff313fdc06b Mon Sep 17 00:00:00 2001 From: guo-shaoge Date: Mon, 19 Aug 2024 18:25:42 +0800 Subject: [PATCH] system-variables: add tiflash_hashagg_preaggregation_mode (#18441) --- system-variables.md | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/system-variables.md b/system-variables.md index d3a73d1b88d7e..668f52d54db27 100644 --- a/system-variables.md +++ b/system-variables.md @@ -6158,6 +6158,19 @@ For details, see [Identify Slow Queries](/identify-slow-queries.md). +### tiflash_hashagg_preaggregation_mode New in v8.3.0 + +- Scope: SESSION | GLOBAL +- Persists to cluster: Yes +- Applies to hint [SET_VAR](/optimizer-hints.md#set_varvar_namevar_value): Yes +- Type: Enumeration +- Default value: `force_preagg` +- Value options: `force_preagg`, `force_streaming`, `auto` +- This variable controls the pre-aggregation strategy used during the first stage of two-stage or three-stage HashAgg operations pushed down to TiFlash: + - `force_preagg`: TiFlash forces pre-aggregation during the first stage of HashAgg. This behavior is consistent with the behavior before v8.3.0. + - `force_streaming`: TiFlash directly sends data to the next stage of HashAgg without pre-aggregation. + - `auto`: TiFlash automatically chooses whether to perform pre-aggregation based on the current workload's aggregation degree. + ### tikv_client_read_timeout New in v7.4.0 - Scope: SESSION | GLOBAL