HAWQ中的EntryDB是什么？主段中主和查询执行程序过程中的EntryDB进程之间有什么区别？在EntryDB上运行了什么样的查询？
entryDB是一种在主节点上派遣的查询执行程序。段中的EntryDB和QE之间的区别在于，EntryDB能够访问主目录。通常将UDF派往EntryDB。
有时计划在EntryDB上执行带有UDF或串行的查询。实际上，UDF/Serial可能被派往QD/QE/EntryDB并在不同的计划中进行处理。
这是一个串行的示例。如您所见，它在orca/planner中明确使用EntryDB。
CREATE TABLE some_vectors (
id SERIAL,
x FLOAT8[]
);
NOTICE: CREATE TABLE will create implicit sequence "some_vectors_id_seq" for serial column "some_vectors.id"
CREATE TABLE
INSERT INTO some_vectors(x) VALUES
(ARRAY[1,0,0,0]),
(ARRAY[0,1,0,0]),
(ARRAY[0,0,1,0]),
(ARRAY[0,0,0,2]);
SET optimizer = on;
SET
EXPLAIN ANALYZE INSERT INTO some_vectors(x) VALUES (ARRAY[1,0,0,0]), (ARRAY[0,1,0,0]), (ARRAY[0,0,1,0]), (ARRAY[0,0,0,2]);
QUERY PLAN
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Insert (cost=0.00..0.31 rows=4 width=12)
Rows out: Avg 4.0 rows x 1 workers. Max/Last(seg0:rhuo-mbp/seg0:rhuo-mbp) 4/4 rows with 7.320/7.320 ms to first row, 7.331/7.331 ms to end, start offset by 1.718/1.718 ms.
Executor memory: 1K bytes.
-> Redistribute Motion 1:1 (slice1) (cost=0.00..0.00 rows=4 width=20)
Rows out: Avg 4.0 rows x 1 workers at destination. Max/Last(seg0:rhuo-mbp/seg0:rhuo-mbp) 4/4 rows with 1.044/1.044 ms to first row, 1.046/1.046 ms to end, start offset by 1.718/1.718 ms.
-> Assert (cost=0.00..0.00 rows=4 width=20)
Assert Cond: NOT id IS NULL
Rows out: Avg 4.0 rows x 1 workers. Max/Last(seg-1:rhuo-mbp/seg-1:rhuo-mbp) 4/4 rows with 0.577/0.577 ms to first row, 0.824/0.824 ms to end, start offset by 1.826/1.826 ms.
Executor memory: 1K bytes.
-> Result (cost=0.00..0.00 rows=4 width=20)
Rows out: Avg 4.0 rows x 1 workers. Max/Last(seg-1:rhuo-mbp/seg-1:rhuo-mbp) 4/4 rows with 0.569/0.569 ms to first row, 0.815/0.815 ms to end, start offset by 1.826/1.826 ms.
-> Append (cost=0.00..0.00 rows=4 width=8)
Rows out: Avg 4.0 rows x 1 workers. Max/Last(seg-1:rhuo-mbp/seg-1:rhuo-mbp) 4/4 rows with 0.360/0.360 ms to first row, 0.402/0.402 ms to end, start offset by 1.827/1.827 ms.
-> Result (cost=0.00..0.00 rows=1 width=8)
Rows out: Avg 1.0 rows x 1 workers. Max/Last(seg-1:rhuo-mbp/seg-1:rhuo-mbp) 1/1 rows with 0.359/0.359 ms to first row, 0.360/0.360 ms to end, start offset by 1.827/1.827 ms.
-> Result (cost=0.00..0.00 rows=1 width=1)
Rows out: Avg 1.0 rows x 1 workers. Max/Last(seg-1:rhuo-mbp/seg-1:rhuo-mbp) 1/1 rows with 0/0 ms to end, start offset by 1.827/1.827 ms.
-> Result (cost=0.00..0.00 rows=1 width=8)
Rows out: Avg 1.0 rows x 1 workers. Max/Last(seg-1:rhuo-mbp/seg-1:rhuo-mbp) 1/1 rows with 0.015/0.015 ms to end, start offset by 2.411/2.411 ms.
-> Result (cost=0.00..0.00 rows=1 width=1)
Rows out: Avg 1.0 rows x 1 workers. Max/Last(seg-1:rhuo-mbp/seg-1:rhuo-mbp) 1/1 rows with 0/0 ms to end, start offset by 2.411/2.411 ms.
-> Result (cost=0.00..0.00 rows=1 width=8)
Rows out: Avg 1.0 rows x 1 workers. Max/Last(seg-1:rhuo-mbp/seg-1:rhuo-mbp) 1/1 rows with 0.012/0.012 ms to end, start offset by 2.500/2.500 ms.
-> Result (cost=0.00..0.00 rows=1 width=1)
Rows out: Avg 1.0 rows x 1 workers. Max/Last(seg-1:rhuo-mbp/seg-1:rhuo-mbp) 1/1 rows with 0/0 ms to end, start offset by 2.500/2.500 ms.
-> Result (cost=0.00..0.00 rows=1 width=8)
Rows out: Avg 1.0 rows x 1 workers. Max/Last(seg-1:rhuo-mbp/seg-1:rhuo-mbp) 1/1 rows with 0.013/0.013 ms to end, start offset by 2.581/2.581 ms.
-> Result (cost=0.00..0.00 rows=1 width=1)
Rows out: Avg 1.0 rows x 1 workers. Max/Last(seg-1:rhuo-mbp/seg-1:rhuo-mbp) 1/1 rows with 0/0 ms to end, start offset by 2.581/2.581 ms.
Slice statistics:
(slice0) Executor memory: 323K bytes (seg0:rhuo-mbp).
(slice1) Executor memory: 279K bytes (entry db).
Statement statistics:
Memory used: 262144K bytes
Settings: default_hash_table_bucket_number=6; optimizer=on
Optimizer status: PQO version 1.633
Dispatcher statistics:
executors used(total/cached/new connection): (2/2/0); dispatcher time(total/connection/dispatch data): (0.120 ms/0.000 ms/0.033 ms).
dispatch data time(max/min/avg): (0.026 ms/0.005 ms/0.015 ms); consume executor data time(max/min/avg): (0.023 ms/0.013 ms/0.018 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): (560.000 B/560 B/560 B); segment size with penalty(avg/min/max): (560.000 B/560 B/560 B); continuity(avg/min/max): (1.000/1.000/1.000); DFS metadatacache: 6.804 ms; resource allocation: 0.549 ms; datalocality calculation: 0.083 ms.
Total runtime: 31.656 ms
(42 rows)
SET optimizer = off;
SET
EXPLAIN ANALYZE INSERT INTO some_vectors(x) VALUES (ARRAY[1,0,0,0]), (ARRAY[0,1,0,0]), (ARRAY[0,0,1,0]), (ARRAY[0,0,0,2]);
QUERY PLAN
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Insert (slice0; segments: 1) (rows=4 width=32)
-> Redistribute Motion 1:1 (slice1) (cost=0.00..0.07 rows=4 width=32)
Rows out: Avg 4.0 rows x 1 workers at destination. Max/Last(seg0:rhuo-mbp/seg0:rhuo-mbp) 4/4 rows with 1.212/1.212 ms to first row, 1.215/1.215 ms to end, start offset by 1.643/1.643 ms.
-> Values Scan on "*VALUES*" (cost=0.00..0.07 rows=4 width=32)
Rows out: Avg 4.0 rows x 1 workers. Max/Last(seg-1:rhuo-mbp/seg-1:rhuo-mbp) 4/4 rows with 0.628/0.628 ms to first row, 0.888/0.888 ms to end, start offset by 1.848/1.848 ms.
Slice statistics:
(slice0) Executor memory: 255K bytes (seg0:rhuo-mbp).
(slice1) Executor memory: 201K bytes (entry db).
Statement statistics:
Memory used: 262144K bytes
Settings: default_hash_table_bucket_number=6; optimizer=off
Optimizer status: legacy query optimizer
Dispatcher statistics:
executors used(total/cached/new connection): (2/2/0); dispatcher time(total/connection/dispatch data): (0.118 ms/0.000 ms/0.025 ms).
dispatch data time(max/min/avg): (0.018 ms/0.006 ms/0.012 ms); consume executor data time(max/min/avg): (0.723 ms/0.022 ms/0.372 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): (280.000 B/280 B/280 B); segment size with penalty(avg/min/max): (280.000 B/280 B/280 B); continuity(avg/min/max): (1.000/1.000/1.000); DFS metadatacache: 0.053 ms; resource allocation: 0.560 ms; datalocality calculation: 0.073 ms.
Total runtime: 33.478 ms
(18 rows)