我有一个分区表tbl_ShiftAssignment。使用数据类型TIMESTAMP WITHOUT TIMEZONE对列Shift_Date进行分区
我正在使用PostgreSQL 9.6.12
explain analyze
select * from tbl_shiftassignment
where shift_date = to_date('15/01/19','dd/mm/yy')
即使它是TIMESTAMP WITHOUT TIMEZONE，我也需要从我的前端使用TO_DATE（），否则没有输出。如果我不使用TO_DATE（），它只扫描单个分区。
现在看看解释分析差异
'''sql解释分析select * from tbl_shiftassignment其中shift_date = to_date（'15 / 01/19'，'dd / mm / yy'）''''
> "Append (cost=0.00..1000.01 rows=185 width=251) (actual
> time=0.611..1.106 rows=66 loops=1)" " -> Seq Scan on
> tbl_shiftassignment (cost=0.00..0.00 rows=1 width=308) (actual
> time=0.015..0.015 rows=0 loops=1)" " Filter: (shift_date =
> to_date('15/01/19'::text, 'dd/mm/yy'::text))" " -> Index Scan using
> isd_tbl_shiftassignment_2007 on tbl_shiftassignment_2007
> (cost=0.15..8.17 rows=1 width=308) (actual time=0.055..0.055 rows=0
> loops=1)" " Index Cond: (shift_date = to_date('15/01/19'::text,
> 'dd/mm/yy'::text))" " -> Index Scan using
> isd_tbl_shiftassignment_2008 on tbl_shiftassignment_2008
> (cost=0.15..8.17 rows=1 width=308) (actual time=0.004..0.005 rows=0
> loops=1)" " Index Cond: (shift_date = to_date('15/01/19'::text,
> 'dd/mm/yy'::text))" " -> Index Scan using
> isd_tbl_shiftassignment_2009 on tbl_shiftassignment_2009
> (cost=0.15..8.17 rows=1 width=308) (actual time=0.003..0.003 rows=0
> loops=1)" " Index Cond: (shift_date = to_date('15/01/19'::text,
> 'dd/mm/yy'::text))" " -> Index Scan using
> isd_tbl_shiftassignment_2010 on tbl_shiftassignment_2010
> (cost=0.15..8.17 rows=1 width=308) (actual time=0.003..0.003 rows=0
> loops=1)" " Index Cond: (shift_date = to_date('15/01/19'::text,
> 'dd/mm/yy'::text))" " -> Index Scan using
> isd_tbl_shiftassignment_2011 on tbl_shiftassignment_2011
> (cost=0.15..8.17 rows=1 width=308) (actual time=0.006..0.006 rows=0
> loops=1)" " Index Cond: (shift_date = to_date('15/01/19'::text,
> 'dd/mm/yy'::text))" " -> Index Scan using
> isd_tbl_shiftassignment_2012 on tbl_shiftassignment_2012
> (cost=0.15..8.17 rows=1 width=308) (actual time=0.004..0.004 rows=0
> loops=1)" " Index Cond: (shift_date = to_date('15/01/19'::text,
> 'dd/mm/yy'::text))" " -> Index Scan using
> isd_tbl_shiftassignment_2013 on tbl_shiftassignment_2013
> (cost=0.15..8.17 rows=1 width=308) (actual time=0.005..0.005 rows=0
> loops=1)" " Index Cond: (shift_date = to_date('15/01/19'::text,
> 'dd/mm/yy'::text))" " -> Index Scan using
> isd_tbl_shiftassignment_2014 on tbl_shiftassignment_2014
> (cost=0.15..8.17 rows=1 width=308) (actual time=0.004..0.004 rows=0
> loops=1)" " Index Cond: (shift_date = to_date('15/01/19'::text,
> 'dd/mm/yy'::text))" " -> Index Scan using
> isd_tbl_shiftassignment_2015 on tbl_shiftassignment_2015
> (cost=0.15..8.17 rows=1 width=308) (actual time=0.003..0.003 rows=0
> loops=1)" " Index Cond: (shift_date = to_date('15/01/19'::text,
> 'dd/mm/yy'::text))" " -> Index Scan using
> isd_tbl_shiftassignment_2016 on tbl_shiftassignment_2016
> (cost=0.28..8.29 rows=1 width=183) (actual time=0.014..0.014 rows=0
> loops=1)" " Index Cond: (shift_date = to_date('15/01/19'::text,
> 'dd/mm/yy'::text))" " -> Index Scan using
> isd_tbl_shiftassignment_201701 on tbl_shiftassignment_201701
> (cost=0.28..8.19 rows=1 width=185) (actual time=0.010..0.010 rows=0
> loops=1)" " Index Cond: (shift_date = to_date('15/01/19'::text,
> 'dd/mm/yy'::text))" " -> Index Scan using
> isd_tbl_shiftassignment_201702 on tbl_shiftassignment_201702
> (cost=0.28..8.30 rows=1 width=190) (actual time=0.008..0.008 rows=0
> loops=1)" " Index Cond: (shift_date = to_date('15/01/19'::text,
> 'dd/mm/yy'::text))" " -> Index Scan using
> isd_tbl_shiftassignment_201703 on tbl_shiftassignment_201703
> (cost=0.28..8.30 rows=1 width=178) (actual time=0.008..0.008 rows=0
> loops=1)" " Index Cond: (shift_date = to_date('15/01/19'::text,
> 'dd/mm/yy'::text))" " -> Index Scan using
> isd_tbl_shiftassignment_201704 on tbl_shiftassignment_201704
> (cost=0.28..8.30 rows=1 width=184) (actual time=0.008..0.008 rows=0
> loops=1)" " Index Cond: (shift_date = to_date('15/01/19'::text,
> 'dd/mm/yy'::text))" " -> Index Scan using
> isd_tbl_shiftassignment_201705 on tbl_shiftassignment_201705
> (cost=0.28..8.30 rows=1 width=180) (actual time=0.051..0.051 rows=0
> loops=1)" " Index Cond: (shift_date = to_date('15/01/19'::text,
> 'dd/mm/yy'::text))" " -> Index Scan using
> isd_tbl_shiftassignment_201706 on tbl_shiftassignment_201706
> (cost=0.28..8.28 rows=1 width=185) (actual time=0.013..0.013 rows=0
> loops=1)" " Index Cond: (shift_date = to_date('15/01/19'::text,
> 'dd/mm/yy'::text))" " -> Index Scan using
> isd_tbl_shiftassignment_201707 on tbl_shiftassignment_201707
> (cost=0.28..8.30 rows=1 width=180) (actual time=0.010..0.010 rows=0
> loops=1)" " Index Cond: (shift_date = to_date('15/01/19'::text,
> 'dd/mm/yy'::text))" " -> Index Scan using
> isd_tbl_shiftassignment_201708 on tbl_shiftassignment_201708
> (cost=0.28..8.30 rows=1 width=185) (actual time=0.016..0.016 rows=0
> loops=1)" " Index Cond: (shift_date = to_date('15/01/19'::text,
> 'dd/mm/yy'::text))" " -> Index Scan using
> isd_tbl_shiftassignment_201709 on tbl_shiftassignment_201709
> (cost=0.28..8.30 rows=1 width=180) (actual time=0.033..0.033 rows=0
> loops=1)" " Index Cond: (shift_date = to_date('15/01/19'::text,
> 'dd/mm/yy'::text))" " -> Index Scan using
> isd_tbl_shiftassignment_201710 on tbl_shiftassignment_201710
> (cost=0.28..8.30 rows=1 width=185) (actual time=0.019..0.019 rows=0
> loops=1)" " Index Cond: (shift_date = to_date('15/01/19'::text,
> 'dd/mm/yy'::text))" " -> Index Scan using
> isd_tbl_shiftassignment_201711 on tbl_shiftassignment_201711
> (cost=0.28..6.06 rows=1 width=185) (actual time=0.010..0.010 rows=0
> loops=1)" " Index Cond: (shift_date = to_date('15/01/19'::text,
> 'dd/mm/yy'::text))" " -> Index Scan using
> isd_tbl_shiftassignment_201712 on tbl_shiftassignment_201712
> (cost=0.28..8.30 rows=1 width=180) (actual time=0.010..0.010 rows=0
> loops=1)" " Index Cond: (shift_date = to_date('15/01/19'::text,
> 'dd/mm/yy'::text))" " -> Index Scan using
> isd_tbl_shiftassignment_201801 on tbl_shiftassignment_201801
> (cost=0.28..8.30 rows=1 width=177) (actual time=0.011..0.011 rows=0
> loops=1)" " Index Cond: (shift_date = to_date('15/01/19'::text,
> 'dd/mm/yy'::text))" " -> Index Scan using
> isd_tbl_shiftassignment_201802 on tbl_shiftassignment_201802
> (cost=0.28..8.30 rows=1 width=185) (actual time=0.011..0.012 rows=0
> loops=1)" " Index Cond: (shift_date = to_date('15/01/19'::text,
> 'dd/mm/yy'::text))" " -> Index Scan using
> isd_tbl_shiftassignment_201803 on tbl_shiftassignment_201803
> (cost=0.28..8.25 rows=1 width=185) (actual time=0.018..0.018 rows=0
> loops=1)" " Index Cond: (shift_date = to_date('15/01/19'::text,
> 'dd/mm/yy'::text))" " -> Index Scan using
> isd_tbl_shiftassignment_201804 on tbl_shiftassignment_201804
> (cost=0.28..8.29 rows=1 width=185) (actual time=0.020..0.020 rows=0
> loops=1)" " Index Cond: (shift_date = to_date('15/01/19'::text,
> 'dd/mm/yy'::text))" " -> Index Scan using
> isd_tbl_shiftassignment_201805 on tbl_shiftassignment_201805
> (cost=0.28..8.30 rows=1 width=184) (actual time=0.012..0.012 rows=0
> loops=1)" " Index Cond: (shift_date = to_date('15/01/19'::text,
> 'dd/mm/yy'::text))" " -> Index Scan using
> isd_tbl_shiftassignment_201806 on tbl_shiftassignment_201806
> (cost=0.28..8.26 rows=1 width=180) (actual time=0.012..0.012 rows=0
> loops=1)" " Index Cond: (shift_date = to_date('15/01/19'::text,
> 'dd/mm/yy'::text))" " -> Index Scan using
> isd_tbl_shiftassignment_201807 on tbl_shiftassignment_201807
> (cost=0.28..8.30 rows=1 width=178) (actual time=0.019..0.019 rows=0
> loops=1)" " Index Cond: (shift_date = to_date('15/01/19'::text,
> 'dd/mm/yy'::text))" " -> Index Scan using
> isd_tbl_shiftassignment_201808 on tbl_shiftassignment_201808
> (cost=0.28..8.30 rows=1 width=179) (actual time=0.014..0.014 rows=0
> loops=1)" " Index Cond: (shift_date = to_date('15/01/19'::text,
> 'dd/mm/yy'::text))" " -> Index Scan using
> isd_tbl_shiftassignment_201809 on tbl_shiftassignment_201809
> (cost=0.28..8.26 rows=1 width=185) (actual time=0.078..0.078 rows=0
> loops=1)" " Index Cond: (shift_date = to_date('15/01/19'::text,
> 'dd/mm/yy'::text))" " -> Index Scan using
> isd_tbl_shiftassignment_201810 on tbl_shiftassignment_201810
> (cost=0.28..8.21 rows=1 width=185) (actual time=0.018..0.018 rows=0
> loops=1)" " Index Cond: (shift_date = to_date('15/01/19'::text,
> 'dd/mm/yy'::text))" " -> Index Scan using
> isd_tbl_shiftassignment_201811 on tbl_shiftassignment_201811
> (cost=0.28..8.22 rows=1 width=184) (actual time=0.017..0.017 rows=0
> loops=1)" " Index Cond: (shift_date = to_date('15/01/19'::text,
> 'dd/mm/yy'::text))" " -> Index Scan using
> isd_tbl_shiftassignment_201812 on tbl_shiftassignment_201812
> (cost=0.28..8.30 rows=1 width=184) (actual time=0.017..0.017 rows=0
> loops=1)" " Index Cond: (shift_date = to_date('15/01/19'::text,
> 'dd/mm/yy'::text))" " -> Bitmap Heap Scan on
> tbl_shiftassignment_201901 (cost=4.79..35.78 rows=66 width=186)
> (actual time=0.040..0.086 rows=66 loops=1)" " Recheck Cond:
> (shift_date = to_date('15/01/19'::text, 'dd/mm/yy'::text))" "
> Heap Blocks: exact=12" " -> Bitmap Index Scan on
> isd_tbl_shiftassignment_201901 (cost=0.00..4.78 rows=66 width=0)
> (actual time=0.030..0.030 rows=66 loops=1)" " Index Cond:
> (shift_date = to_date('15/01/19'::text, 'dd/mm/yy'::text))" " ->
> Index Scan using isd_tbl_shiftassignment_201902 on
> tbl_shiftassignment_201902 (cost=0.28..8.30 rows=1 width=185) (actual
> time=0.014..0.014 rows=0 loops=1)" " Index Cond: (shift_date =
> to_date('15/01/19'::text, 'dd/mm/yy'::text))" " -> Index Scan using
> isd_tbl_shiftassignment_201903 on tbl_shiftassignment_201903
> (cost=0.15..8.17 rows=1 width=308) (actual time=0.006..0.006 rows=0
> loops=1)" " Index Cond: (shift_date = to_date('15/01/19'::text,
> 'dd/mm/yy'::text))" " -> Index Scan using
> isd_tbl_shiftassignment_201904 on tbl_shiftassignment_201904
> (cost=0.15..8.17 rows=1 width=308) (actual time=0.005..0.005 rows=0
> loops=1)" " Index Cond: (shift_date = to_date('15/01/19'::text,
> 'dd/mm/yy'::text))" " -> Index Scan using
> isd_tbl_shiftassignment_201905 on tbl_shiftassignment_201905
> (cost=0.15..8.17 rows=1 width=308) (actual time=0.005..0.005 rows=0
> loops=1)" " Index Cond: (shift_date = to_date('15/01/19'::text,
> 'dd/mm/yy'::text))" " -> Index Scan using
> isd_tbl_shiftassignment_201906 on tbl_shiftassignment_201906
> (cost=0.15..8.17 rows=1 width=308) (actual time=0.005..0.005 rows=0
> loops=1)" " Index Cond: (shift_date = to_date('15/01/19'::text,
> 'dd/mm/yy'::text))" " -> Index Scan using
> isd_tbl_shiftassignment_201907 on tbl_shiftassignment_201907
> (cost=0.15..8.17 rows=1 width=308) (actual time=0.003..0.003 rows=0
> loops=1)" " Index Cond: (shift_date = to_date('15/01/19'::text,
> 'dd/mm/yy'::text))" " -> Index Scan using
> isd_tbl_shiftassignment_201908 on tbl_shiftassignment_201908
> (cost=0.15..8.17 rows=1 width=308) (actual time=0.004..0.004 rows=0
> loops=1)" " Index Cond: (shift_date = to_date('15/01/19'::text,
> 'dd/mm/yy'::text))" " -> Index Scan using
> isd_tbl_shiftassignment_201909 on tbl_shiftassignment_201909
> (cost=0.15..8.17 rows=1 width=308) (actual time=0.005..0.005 rows=0
> loops=1)" " Index Cond: (shift_date = to_date('15/01/19'::text,
> 'dd/mm/yy'::text))" " -> Index Scan using
> isd_tbl_shiftassignment_201910 on tbl_shiftassignment_201910
> (cost=0.15..8.17 rows=1 width=308) (actual time=0.004..0.004 rows=0
> loops=1)" " Index Cond: (shift_date = to_date('15/01/19'::text,
> 'dd/mm/yy'::text))" " -> Index Scan using
> isd_tbl_shiftassignment_201911 on tbl_shiftassignment_201911
> (cost=0.15..8.17 rows=1 width=308) (actual time=0.005..0.005 rows=0
> loops=1)" " Index Cond: (shift_date = to_date('15/01/19'::text,
> 'dd/mm/yy'::text))" " -> Index Scan using
> isd_tbl_shiftassignment_201912 on tbl_shiftassignment_201912
> (cost=0.15..8.17 rows=1 width=308) (actual time=0.005..0.005 rows=0
> loops=1)" " Index Cond: (shift_date = to_date('15/01/19'::text,
> 'dd/mm/yy'::text))" " -> Index Scan using
> isd_tbl_shiftassignment_202001 on tbl_shiftassignment_202001
> (cost=0.15..8.17 rows=1 width=308) (actual time=0.005..0.005 rows=0
> loops=1)" " Index Cond: (shift_date = to_date('15/01/19'::text,
> 'dd/mm/yy'::text))" " -> Index Scan using
> isd_tbl_shiftassignment_202002 on tbl_shiftassignment_202002
> (cost=0.15..8.17 rows=1 width=308) (actual time=0.005..0.005 rows=0
> loops=1)" " Index Cond: (shift_date = to_date('15/01/19'::text,
> 'dd/mm/yy'::text))" " -> Index Scan using
> isd_tbl_shiftassignment_202003 on tbl_shiftassignment_202003
> (cost=0.15..8.17 rows=1 width=308) (actual time=0.004..0.004 rows=0
> loops=1)" " Index Cond: (shift_date = to_date('15/01/19'::text,
> 'dd/mm/yy'::text))" " -> Index Scan using
> isd_tbl_shiftassignment_202004 on tbl_shiftassignment_202004
> (cost=0.15..8.17 rows=1 width=308) (actual time=0.005..0.005 rows=0
> loops=1)" " Index Cond: (shift_date = to_date('15/01/19'::text,
> 'dd/mm/yy'::text))" " -> Index Scan using
> isd_tbl_shiftassignment_202005 on tbl_shiftassignment_202005
> (cost=0.15..8.17 rows=1 width=308) (actual time=0.006..0.007 rows=0
> loops=1)" " Index Cond: (shift_date = to_date('15/01/19'::text,
> 'dd/mm/yy'::text))" " -> Index Scan using
> isd_tbl_shiftassignment_202006 on tbl_shiftassignment_202006
> (cost=0.15..8.17 rows=1 width=308) (actual time=0.003..0.003 rows=0
> loops=1)" " Index Cond: (shift_date = to_date('15/01/19'::text,
> 'dd/mm/yy'::text))" " -> Index Scan using
> isd_tbl_shiftassignment_202007 on tbl_shiftassignment_202007
> (cost=0.15..8.17 rows=1 width=308) (actual time=0.004..0.004 rows=0
> loops=1)" " Index Cond: (shift_date = to_date('15/01/19'::text,
> 'dd/mm/yy'::text))" " -> Index Scan using
> isd_tbl_shiftassignment_202008 on tbl_shiftassignment_202008
> (cost=0.15..8.17 rows=1 width=308) (actual time=0.005..0.005 rows=0
> loops=1)" " Index Cond: (shift_date = to_date('15/01/19'::text,
> 'dd/mm/yy'::text))" " -> Index Scan using
> isd_tbl_shiftassignment_202009 on tbl_shiftassignment_202009
> (cost=0.15..8.17 rows=1 width=308) (actual time=0.003..0.004 rows=0
> loops=1)" " Index Cond: (shift_date = to_date('15/01/19'::text,
> 'dd/mm/yy'::text))" " -> Index Scan using
> isd_tbl_shiftassignment_202010 on tbl_shiftassignment_202010
> (cost=0.15..8.17 rows=1 width=308) (actual time=0.003..0.003 rows=0
> loops=1)" " Index Cond: (shift_date = to_date('15/01/19'::text,
> 'dd/mm/yy'::text))" " -> Index Scan using
> isd_tbl_shiftassignment_202011 on tbl_shiftassignment_202011
> (cost=0.15..8.17 rows=1 width=308) (actual time=0.004..0.004 rows=0
> loops=1)" " Index Cond: (shift_date = to_date('15/01/19'::text,
> 'dd/mm/yy'::text))" " -> Index Scan using
> isd_tbl_shiftassignment_202012 on tbl_shiftassignment_202012
> (cost=0.15..8.17 rows=1 width=308) (actual time=0.003..0.003 rows=0
> loops=1)"
>
> " -> Index Scan using isd_tbl_shiftassignment_posdata on
> tbl_shiftassignment_posdata (cost=0.15..8.17 rows=1 width=308)
> (actual time=0.004..0.004 rows=0 loops=1)" " Index Cond:
> (shift_date = to_date('15/01/19'::text, 'dd/mm/yy'::text))" "Planning
> time: 68.388 ms" "Execution time: 4.535 ms"
=============================================
然而，如果我不像这样使用TO_DATE（）......
explain analyze
select * from tbl_shiftassignment
where shift_date = '15-JAN-19';
"Append (cost=0.00..35.61 rows=67 width=187) (actual time=0.023..0.041 rows=66 loops=1)"
" -> Seq Scan on tbl_shiftassignment (cost=0.00..0.00 rows=1 width=308) (actual time=0.006..0.006 rows=0 loops=1)"
" Filter: (shift_date = '2019-01-15 00:00:00'::timestamp without time zone)"
" -> Bitmap Heap Scan on tbl_shiftassignment_201901 (cost=4.79..35.61 rows=66 width=186) (actual time=0.016..0.032 rows=66 loops=1)"
" Recheck Cond: (shift_date = '2019-01-15 00:00:00'::timestamp without time zone)"
" Heap Blocks: exact=12"
" -> Bitmap Index Scan on isd_tbl_shiftassignment_201901 (cost=0.00..4.77 rows=66 width=0) (actual time=0.011..0.011 rows=66 loops=1)"
" Index Cond: (shift_date = '2019-01-15 00:00:00'::timestamp without time zone)"
"Planning time: 7.388 ms"
"Execution time: 0.088 ms"
如果未使用TO_DATE（），仅影响10行
虽然，索引扫描很快，我的问题是如果我切换到pg11，它会像第二个例子（只有10行受影响）一样工作，即使我使用TO_DATE（）
Same problem for Date Range
WHERE Shift_Date >= TO_DATE('25/08/2018','DD/MM/YYYY')
AND Shift_Date <= TO_DATE('30/08/2018','DD/MM/YYYY')
是的，这是PostgreSQL v11中的新功能：分区修剪也可以在执行时进行。
在PostgreSQL v10中，分区修剪只能在计划查询时进行。由于to_date是STABLE而不是IMMUTABLE，因此在计划时执行可能会导致与执行时不同的值，因此规划人员无法对其进行优化。
如果您使用date文字编写查询，它应该在v10中工作。