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commit adfa6c83ec8ca371798b17021d49a8eacd954faf
Author: Csaba Ringhofer <csringho...@cloudera.com>
AuthorDate: Thu Jun 1 11:52:23 2023 +0200
IMPALA-12142: Decrease default fetch_size to 8192 in impala-shell
The previous fetch_size of 10240 turned out to be suboptimal for HS2
server side, likely because it leads to overallocation in result
'std::vector's. Changed to the closest power of 2 size (8192).
With this change RowMaterializationTimer decreased from 3.4s to 2.7s
for "SELECT * FROM tpch_parquet.lineitem".
Change-Id: I34973cb705db53c496b9944c74995b45cf720d46
Reviewed-on: http://gerrit.cloudera.org:8080/19965
Reviewed-by: Kurt Deschler <kdesc...@cloudera.com>
Reviewed-by: Daniel Becker <daniel.bec...@cloudera.com>
Tested-by: Impala Public Jenkins <impala-public-jenk...@cloudera.com>
---
shell/option_parser.py | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/shell/option_parser.py b/shell/option_parser.py
index 75ede820a..1fc6fde2d 100755
--- a/shell/option_parser.py
+++ b/shell/option_parser.py
@@ -320,7 +320,7 @@ def get_option_parser(defaults):
"enforce any http path for the incoming requests,
deployments could "
"still put it behind a loadbalancer that can expect the
traffic at a "
"certain path.")
- parser.add_option("--fetch_size", type="int", dest="fetch_size",
default=10240,
+ parser.add_option("--fetch_size", type="int", dest="fetch_size",
default=8192,
help="The fetch size when fetching rows from the Impala
coordinator. "
"The fetch size controls how many rows a single fetch RPC
request "
"(RPC from the Impala shell to the Impala coordinator)
reads at a "
@@ -328,7 +328,7 @@ def get_option_parser(defaults):
"('spool_query_results'=true). When result spooling is
enabled "
"values over the batch_size are honored. When result
spooling is "
"disabled, values over the batch_size have no affect. By
default, "
- "the fetch_size is set to 10240 which is equivalent to 10
row "
+ "the fetch_size is set to 8192 which is equivalent to 8
row "
"batches (assuming the default batch size). Note that if
result "
"spooling is disabled only a single row batch can be
fetched at a "
"time regardless of the specified fetch_size.")
