WebJan 22, 2015 · "Heap Blocks: exact=1" means that it only visited one block, and that it was not lossy. (So both of yours rows returned were in the same block) This agrees with the Buffers data. The Bitmap Index Scans and BitmapAnd in total hit 7 blocks. The Heap Scan hit one more, bringing it up to 8. WebDec 26, 2005 · > This is PostgreSQL 8.1.0. > - what does "Bitmap Heap Scan" phase do? A plain indexscan fetches one tuple-pointer at a time from the index, and immediately visits that tuple in the table. A bitmap scan fetches all the tuple-pointers from the index in one go, sorts them using an in-memory "bitmap" data structure, and then visits the table tuples in
Bitmap Indexes - PostgreSQL wiki
WebMar 28, 2024 · Исходная таблица с документами. create table docs_initial ( doc_id integer not null, doc_date date not null, doc_number varchar(15) not null, doc_text text not null, constraint docs_initial_pk primary key (doc_id) ); create unique index idx_doc_number_initial on docs_initial using btree (doc_number); create index idx_doc_date_initial on … WebAug 28, 2024 · Bitmap Heap Scan: As the name implies, it reads through bitmap of pages and then scans data from heap corresponding to stored page and offset. At the end, it … can buggy be killed
PostgreSQL Bitmap Heap Scan on index is very slow but Index …
WebApr 19, 2024 · Поэтому в таком случае оптимизатор переключается на сканирование по битовой карте (bitmap scan): postgres=# explain (costs off) select * from t where a … WebFeb 9, 2024 · The heap-access portion of an index scan thus involves a lot of random access into the heap, which can be slow, particularly on traditional rotating media. (As described in Section 11.5, bitmap scans try to alleviate this cost by doing the heap accesses in sorted order, but that only goes so far.) WebSep 17, 2024 · There are several things that can work together in this: work_mem is too low for the bitmap heap scan to be as effective as PostgreSQL things it should be (Heap Blocks: lossy=33133). If work_mem is too small to contain a bitmap that has one bit per table row, PostgreSQL will at some point degrade the bitmap to one bit per 8kB block. … fishing major and minor feeding times