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The following commit(s) were added to refs/heads/branch-2.0 by this push:
new c6622dbe459 [opt](coord) use single instance only with small limit
#33888 (#33903)
c6622dbe459 is described below
commit c6622dbe45968b5ed1246b640e78c7d978908d9c
Author: Mingyu Chen <[email protected]>
AuthorDate: Fri Apr 19 22:22:08 2024 +0800
[opt](coord) use single instance only with small limit #33888 (#33903)
---
.../src/main/java/org/apache/doris/planner/ScanNode.java | 5 +++--
fe/fe-core/src/main/java/org/apache/doris/qe/Coordinator.java | 4 ++--
.../src/main/java/org/apache/doris/qe/SessionVariable.java | 11 +++++++++++
3 files changed, 16 insertions(+), 4 deletions(-)
diff --git a/fe/fe-core/src/main/java/org/apache/doris/planner/ScanNode.java
b/fe/fe-core/src/main/java/org/apache/doris/planner/ScanNode.java
index 99184df1453..1c5ee53e34b 100644
--- a/fe/fe-core/src/main/java/org/apache/doris/planner/ScanNode.java
+++ b/fe/fe-core/src/main/java/org/apache/doris/planner/ScanNode.java
@@ -708,7 +708,8 @@ public abstract class ScanNode extends PlanNode {
return isKeySearch() || !enableShardScan;
}
- public boolean shouldUseOneInstance() {
- return hasLimit() && conjuncts.isEmpty();
+ public boolean shouldUseOneInstance(ConnectContext ctx) {
+ long limitRowsForSingleInstance = ctx == null ? 10000 :
ctx.getSessionVariable().limitRowsForSingleInstance;
+ return hasLimit() && getLimit() < limitRowsForSingleInstance &&
conjuncts.isEmpty();
}
}
diff --git a/fe/fe-core/src/main/java/org/apache/doris/qe/Coordinator.java
b/fe/fe-core/src/main/java/org/apache/doris/qe/Coordinator.java
index cd3b8f38770..164072c0b5c 100644
--- a/fe/fe-core/src/main/java/org/apache/doris/qe/Coordinator.java
+++ b/fe/fe-core/src/main/java/org/apache/doris/qe/Coordinator.java
@@ -1759,7 +1759,7 @@ public class Coordinator implements CoordInterface {
}
// if have limit and no conjuncts, only need 1
instance to save cpu and
// mem resource
- if (node.isPresent() &&
node.get().shouldUseOneInstance()) {
+ if (node.isPresent() &&
node.get().shouldUseOneInstance(ConnectContext.get())) {
expectedInstanceNum = 1;
}
@@ -1772,7 +1772,7 @@ public class Coordinator implements CoordInterface {
expectedInstanceNum =
Math.max(expectedInstanceNum, 1);
// if have limit and conjuncts, only need 1
instance to save cpu and
// mem resource
- if (node.isPresent() &&
node.get().shouldUseOneInstance()) {
+ if (node.isPresent() &&
node.get().shouldUseOneInstance(ConnectContext.get())) {
expectedInstanceNum = 1;
}
diff --git a/fe/fe-core/src/main/java/org/apache/doris/qe/SessionVariable.java
b/fe/fe-core/src/main/java/org/apache/doris/qe/SessionVariable.java
index efcfec7570e..633389812e3 100644
--- a/fe/fe-core/src/main/java/org/apache/doris/qe/SessionVariable.java
+++ b/fe/fe-core/src/main/java/org/apache/doris/qe/SessionVariable.java
@@ -461,6 +461,9 @@ public class SessionVariable implements Serializable,
Writable {
);
public static final String ENABLE_STATS = "enable_stats";
+
+ public static final String LIMIT_ROWS_FOR_SINGLE_INSTANCE =
"limit_rows_for_single_instance";
+
/**
* If set false, user couldn't submit analyze SQL and FE won't allocate
any related resources.
*/
@@ -1355,6 +1358,14 @@ public class SessionVariable implements Serializable,
Writable {
"当变量为true时，show processlist命令展示所有fe的连接"})
public boolean showAllFeConnection = false;
+ @VariableMgr.VarAttr(name = LIMIT_ROWS_FOR_SINGLE_INSTANCE,
+ description = {"当一个 ScanNode 上没有过滤条件，且 limit 值小于这个阈值时，"
+ + "系统会将这个算子的并发度调整为1，以减少简单查询的扇出",
+ "When a ScanNode has no filter conditions and the limit
value is less than this threshold, "
+ + "the system will adjust the concurrency of this
operator to 1 "
+ + "to reduce the fan-out of simple queries"})
+ public long limitRowsForSingleInstance = 10000;
+
public Set<Integer> getIgnoredRuntimeFilterIds() {
return Arrays.stream(ignoreRuntimeFilterIds.split(",[\\s]*"))
.map(v -> {
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