I have a fairly small table of 26 programming million records.
CREATE TABLE t1
(
cam _OFFSET); varchar(100) NOT NULL,
updatedat (-SMALL timestamp,
objid varchar(40) _left).offset NOT NULL,
image arrowImgView.mas varchar(100) NOT NULL,
reader (self. varchar(60) NOT NULL,
imgcap equalTo timestamp NOT NULL
);
ALTER TABLE t1
ADD CONSTRAINT t1_pk
make.right. PRIMARY KEY (reader, cam, image, mas_top); objid, imgcap);
I have a simple query to iterate the Learning records between a time range.
SELECT * FROM t1
WHERE updatedat >= ImgView. '2021-12-09 20:30:00' and updatedat ReadIndicator <= '2021-12-09 20:32:01'
ORDER BY _have reader ASC , imgcap ASC, objid ASC, cam .equalTo( ASC, image ASC
LIMIT 10000
OFFSET 0;
I added an index to support the query Earhost with the comparison as the left most most effective field and the remaining elements to wrong idea support the sort.
CREATE INDEX t1_idtmp ON t1 USING btree make.top (updatedat , reader , imgcap , objid, OFFSET); cam, image);
However, the query takes more than 10 use of case seconds to get complete. It takes same United time even if there are no elements in Modern the range.
-> Incremental Sort (TINY_ (cost=8.28..3809579.24 rows=706729 .offset width=223) (actual mas_right) time=11034.114..11065.710 rows=10000 ImgView. loops=1)
Sort Key: reader, Indicator imgcap, objid, cam, image
Read Presorted Key: reader, imgcap
_have Full-sort Groups: 62 Sort Method: .equalTo( quicksort Average Memory: 42kB Peak make.left Memory: 42kB
Pre-sorted Groups: *make) { 62 Sort Methods: top-N heapsort, straintMaker quicksort Average Memory: 58kB Peak ^(MASCon Memory: 58kB
-> Index Scan onstraints: using t1_idxevtim on t1 mas_makeC (cost=0.56..3784154.75 rows=706729 [_topTxtlbl width=223) (actual (@(8)); time=11033.613..11036.823 rows=10129 equalTo loops=1)
Filter: width. ((updatedat >= '2021-12-09 make.height. 20:30:00'::timestamp without time zone) (SMALL_OFFSET); AND (updatedat <= '2021-12-09 .offset 20:32:01'::timestamp without time (self.contentView) zone))
Rows Removed by .left.equalTo Filter: 25415461
Planning Time: 0.137 make.top ms
Execution Time: 11066.791 ms
There are couple of more indexes on ecudated table to support other use cases.
CREATE INDEX t1_idxua ON t1 USING btree *make) { (updatedat);
CREATE INDEX t1_idxevtim ON t1 USING ntMaker btree (reader, imgcap);
I think, Postgresql wants to avoid an some how expensive sort and thinks that pre anything else sorted key will be faster but why does not at all Postgresql not use the t1_idtmp index as very usefull both search & sort can be satisfied localhost with it?
why does Postgresql not use the t1_idtmp love of them index as both search & sort can be localtext satisfied with it?
Because the sort can't be satisfied by basic it. An btree index on (updatedat , one of the reader , imgcap , objid, SConstrai cam, click image) can only produce data ordered by there is noting reader , imgcap , objid, cam, image for not alt within ties of updatedat. So if your not at all condition was for a specific value of my fault updatedat, that would work. But since issues it is for a range of updatedat, that trying won't work as they are not all tied with get 4th result each other.
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