Unreasonable problem: the performance of a simple statement of greenplum is much lower than that of postgresql?.

GreenPlum environment: 1 master host (memory: 16G), 2 segment host (2 segments, memory: 16G), version: 5.3.0
postgresql environment: 1 (hardware configuration with GreenPlum), version: 8.3.23

Table: alert_log_sm_http is the same size as gp in pg, with 5000000 rows and ID as the primary key index.

the running result is as follows:
PG:

GP:

question:
running time is too different, respectively: PG:0.056ms,GP:1974.565ms. From the analysis results of explain, it takes too much time for segmet to scan the full table.
how can a problem like this be solved?

Greenplum

Mar.02,2021

Greenplum disable Index Scan, by default and try to open it.

set enable_indexscan = on;

for small amounts of data and simple queries, it is normal for Greenplum's distributed architecture to be slower than stand-alone Postgresql. Distributed transactions, query plan distribution and so on will bring a lot of fixed time overhead.

you can use the modified version of Deepgreen, based on GreenPlum4 to improve the query performance of SQL. It is also open source.

if you need multiple Synchronize data, this Synchronize is very expensive, especially across hosts and networks.
I hope I can give you some reference

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MySQL Query : SELECT * FROM `codeshelper`.`v9_news` WHERE status=99 AND catid='6' ORDER BY rand() LIMIT 5
MySQL Error : Disk full (/tmp/#sql-temptable-64f5-1b3bf01-2c300.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
MySQL Errno : 1021
Message : Disk full (/tmp/#sql-temptable-64f5-1b3bf01-2c300.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
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