Questions tagged [bitmap-index]
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11 questions
0 votes
1 answer
78 views
PostgreSQL - How to optimize slow Bitmap Heap Scan?
My app is calculating the SuperTrend indicator over the price of multiple cryptocurrencies. I have the following table and indices: -- DDL generated by Postico 2.1.1 -- Not all database features are ...
- 23
0 votes
2 answers
2k views
In PostgreSQL, how can I make Bitmap Index Scan parallelized?
I want to improve the performance of an SQL statement. I am on version 13. Here are the sample codes and the query I am interested in. drop table ords; CREATE TABLE ords ( ORD_ID INT NOT NULL, CUST_ID ...
- 51
0 votes
2 answers
2k views
Postgres 10.6: Why is a particular partition's index not being used?
I'm truly stumped as to what's causing this issue and hoping for some guidance. Firstly, this is in our STAGE environment and we partition this table based on the createdTime every month. I have ...
- 391
9 votes
3 answers
4k views
Indexing of a PostgreSQL bitstring (up to 20,000 bits each)
I am building a table that contains chemical compounds (many millions of rows) and of those compounds certain predetermined features/fragments are flagged in a fixed length bitstring. This bitstring ...
2 votes
1 answer
3k views
When PostgreSQL will use Index Only Scan over Bitmap Index + Heap Scan
Today I've been doing some reading on the difference between the two and I think I've got a reasonable idea of each. Index Only: Accesses heap pages as it moves through the index, possibly access the ...
- 123
1 vote
1 answer
230 views
Mapping between each bit in a bitmap index and tuple-pointers
Bitmap Indexes are described here, but I don't understand some part of it. A plain indexscan fetches one tuple-pointer at a time from the index, and immediately visits that tuple in the table. A ...
- 11
2 votes
1 answer
55 views
Why does PSQL not allow hash indexes with Bitmapscan?
For doing a simple equality query such as EXPLAIN SELECT * FROM table where x = 1; I see that a Bitmap Index scan is done using the BTree indexes. Apparently, Bitmap Index scans disable Hash indexes ...
- 123
-1 votes
1 answer
1k views
Btree index and Bit Map Index [duplicate]
Please clarify the difference between BitMap Index and Btree index. I am using mysql version 5.5.37-0ubuntu0.12.04.1. I can able to create Btree index but unable to create the same, Please find the ...
- 1,187
1 vote
2 answers
5k views
ON creating BITMAP INDEX on a table in mysql throws error
I have database named "demo_dev" and added a table named "countries". I wanted to create a bitmap index on a column, say, region as it has fewer unique values, using following query. CREATE BITMAP ...
- 11
4 votes
0 answers
227 views
How to decode a query on a composite unary-encoded attribute?
A good early paper on the topic of bitmap indexes is "Bit Transposed Files" by Wong et al, published in 1985. In all the query-decoding examples, it is left to the reader to understand how each ...
- 2,438
5 votes
2 answers
4k views
Cardinality rule for bitmap indexes
The Oracle documentation includes the following advice: A bitmap index should be built on each of the foreign key columns of the fact table or tables In that reference, there is even a bitmap ...
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