OushuDB 檢視查詢執行情況

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使用\timing命令可以列印出查詢執行的時間。

test=＃ \timing on

Timing is on.

test=＃ select * from foo; # 這時再執行SQL語句會給出語句執行時間。

 id | name

----+------

  1 | hawq

  2 | hdfs

(2 rows)

Time: 16.369 ms

test=＃ \timing off  # 關閉時間輸出

Timing is off.

使用explain語句可以顯示出查詢計劃。

test=＃ explain select count(*) from foo;

                                    QUERY PLAN

----------------------------------------------------------------------------------

 Aggregate  (cost=1.07..1.08 rows=1 width=8)

   ->  Gather Motion 1:1  (slice1; segments: 1)  (cost=1.03..1.06 rows=1 width=8)

     ->  Aggregate  (cost=1.03..1.04 rows=1 width=8)

           ->  Append-only Scan on foo  (cost=0.00..1.02 rows=2 width=0)

 Settings:  default_hash_table_bucket_number=6

(5 rows)

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test=＃ explain analyze select count(*) from foo;

--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

Aggregate  (cost=1.07..1.08 rows=1 width=8)

Rows out:  Avg 1.0 rows x 1 workers.  Max/Last(seg-1:changlei/seg-1:changlei) 1/1 rows with 5.944/5.944 ms to end, start offset by 6.568/6.568 ms.

->  Gather Motion 1:1  (slice1; segments: 1)  (cost=1.03..1.06 rows=1 width=8)

     Rows out:  Avg 1.0 rows x 1 workers at destination.  Max/Last(seg-1:changlei/seg-1:changlei) 1/1 rows with 5.941/5.941 ms to first row, 5.942/5.942 ms to end, start offset by 6.569/6.569 ms.

     ->  Aggregate  (cost=1.03..1.04 rows=1 width=8)

           Rows out:  Avg 1.0 rows x 1 workers.  Max/Last(seg0:changlei/seg0:changlei) 1/1 rows with 5.035/5.035 ms to first row, 5.036/5.036 ms to end, start offset by 7.396/7.396 ms.

           ->  Append-only Scan on foo  (cost=0.00..1.02 rows=2 width=0)

                 Rows out:  Avg 2.0 rows x 1 workers.  Max/Last(seg0:changlei/seg0:changlei) 2/2 rows with 5.011/5.011 ms to first row, 5.032/5.032 ms to end, start offset by 7.397/7.397 ms.

Slice statistics:

 (slice0)    Executor memory: 223K bytes.

 (slice1)    Executor memory: 279K bytes (seg0:changlei).

Statement statistics:

 Memory used: 262144K bytes

Settings:  default_hash_table_bucket_number=6

Dispatcher statistics:

 executors used(total/cached/new connection): (1/1/0); dispatcher time(total/connection/dispatch data): (1.462 ms/0.000 ms/0.029 ms).

 dispatch data time(max/min/avg): (0.029 ms/0.029 ms/0.029 ms); consume executor data time(max/min/avg): (0.012 ms/0.012 ms/0.012 ms); free executor time(max/min/avg): (0.000 ms/0.000 ms/0.000 ms).

Data locality statistics:

 data locality ratio: 1.000; virtual segment number: 1; different host number: 1; virtual segment number per host(avg/min/max): (1/1/1); segment size(avg/min/max): (56.000 B/56 B/56 B); segment size with penalty(avg/min/max): (56.000 B/56 B/56 B); continuity(avg/min/max): (1.000/1.000/1.000); DFS metadatacache: 0.049 ms; resource allocation: 0.612 ms; datalocality calculation: 0.085 ms.

Total runtime: 13.398 ms

(20 rows)