在postgresql9.5的時候做過一個測試就是sum()的效率最終的測試結果是sum(int)>sum(numeric)>sum(bigint)當時比較詫異為啥sum(bigint)效率比sum(numeric)還低。sum(numeric)的效率比sum(bigint)快了10%。

在pg10版本的時候對sum()的效能做了優化，pg10.4

最終的測試結果為pg10的效率大幅提升，sum(int)>sum(bigint)>sum(numeric)，當一個表中有bigint，int時，誰放在第一列效率要高點。但是差別不是很大，效率都比numeric高。

 

 

bigint for smallint or int arguments, numeric for bigint arguments, otherwise the same as the argument data type

這次主要做abase5.0測試，以及pg11 jit測試。

插入1kw資料測試。

這裡只是輸出型別的轉換，並不會太影響效率。 numeric的算術運算比整數型別要慢很多。 通過求助，最終了解到可能和pg的元組變形(tuple deform)有關, 這次建立三張表分別對應三種資料型別。 create table t_int(n_int int); create table t_bigint(n_bigint bigint); create table t_numeric(n_numeric numeric); insert into t_int select generate_series(1,10000000); insert into t_bigint select generate_series(1,10000000); insert into t_numeric select generate_series(1,10000000);  

https://blog.csdn.net/luojinbai/article/details/42914299   numeric : https://explain.depesz.com/s/Lk6P int:https://explain.depesz.com/s/4Xo4 bigint: https://explain.depesz.com/s/niQI   pg:bigint,numeric,int效率測試： drop table t_int; drop table t_bigint; drop table t_numeric; show shared_buffers;   drop table t_bigint create table t_int(n_int int); create table t_bigint(n_bigint bigint); create table t_numeric(n_numeric numeric); insert into t_int select generate_series(1,10000000); insert into t_bigint select generate_series(1,10000000); insert into t_numeric select generate_series(1,10000000); numeric https://explain.depesz.com/s/Ivks select version(); explain analyze select count(*) from t_num_type   SET max_parallel_workers_per_gather = 2; show max_parallel_workers_per_gather ;   select version(); 1.單表測試 explain (analyze,buffers,format text) select sum(n_int) from t_int;--560 explain (analyze,buffers,format text) select sum(n_bigint) from t_bigint;--575 explain (analyze,buffers,format text) select sum(n_numeric) from t_numeric;--868 sum(int)>sum(bigint)>sum(numeric) 2.一個表測試 drop table t_num_type create table t_num_type(n_bigint bigint,n_numeric numeric,n_int int); insert into t_num_type select n,n,n from generate_series(1,10000000) as t(n) explain (analyze,buffers,format text) select sum(n_int) from t_num_type ;--661 explain (analyze,buffers,format text) select sum(n_bigint) from t_num_type;--625 explain (analyze,buffers,format text) select sum(n_numeric) from t_num_type;--946   sum(bigint)>sum(int)>sum(numeric) 但是整體比單錶慢。 select * from t_num_type_3 limit 10   drop table t_num_type_2 create table t_num_type_2(n_int int,n_numeric numeric,n_bigint bigint); insert into t_num_type_2 select n,n,n from generate_series(1,10000000) as t(n) explain (analyze,buffers,format text) select sum(n_int) from t_num_type_2;--603 explain (analyze,buffers,format text) select sum(n_bigint) from t_num_type_2;--668 explain (analyze,buffers,format text) select sum(n_numeric) from t_num_type_2;--947 sum(int)>sum(bigint)>sum(numeric) --show jit_above_cost int放前面int快，bigint又慢了。   3. create table t_num_type_3(n_bigint bigint,n_int int,n_numeric numeric); insert into t_num_type_3 select n,n,n from generate_series(1,10000000) as t(n) explain (analyze,buffers,format text) select sum(n_int) from t_num_type_3;--623 explain (analyze,buffers,format text) select sum(n_bigint) from t_num_type_3;--616 explain (analyze,buffers,format text) select sum(n_numeric) from t_num_type_3;--973   目前來bigint放到第一列總是快的。當int放到第一列的時候又比bigint快。     create table t_num_type_4(n_int int,n_bigint bigint,n_numeric numeric); insert into t_num_type_4 select n,n,n from generate_series(1,10000000) as t(n) explain (analyze,buffers,format text) select sum(n_int) from t_num_type_4;--617 explain (analyze,buffers,format text) select sum(n_bigint) from t_num_type_4;--643 explain (analyze,buffers,format text) select sum(n_numeric) from t_num_type_4;--973