Index not hit in mysql
When I select all columns, the indexing does not work, but if I select just a few columns, it does. mysql> explain SELECT * FROM fatura USE INDEX (datapago_serv_pago) WHERE id_servidor = 10 AND pago = '1' AND data_pago <=…
Javascript – How to compare two arrays at the index and also include null values in the new array output
So I am very new to coding and have run into an issue when it comes to comparing arrays, especially ones that are nested and trying to pull out values that match using their indices into a new array. Say…
Postgresql – How to search for the acronym of a string column in an indexable way
I'm working on an express.js project, using Sequelize as the orm, and postgres as the engine. I'm working on improving the performance of a slow select query that does many things, and one of them is comparing the acronym of…
Mysql – can a sql sentence use index covering and index condition pushdown simultaneously？
When the query does not meet the conditions for index coverage,if Innodb will use index condition pushdown by auto? or how to explain these two thing by simple word or example.
MySQL prefix index on datetime column
I have a log table with timestamped (DATETIME) rows in the millions which I occasionally need to search by date or date range. I have an index on the timestamp column at present for the purpose. However, I am wondering…
Mysql – SQL indexing with 2 join tables
I have 3 tables. country, team, player table Country id name 1 x 2 x 3 x table Team id name country_id 1 x 1 2 x 1 3 x 1 table Player id name country_id team_id 1 x 1…
Rails 7 + PostgreSQL: Super slow searching data in a table having 1,2M rows. How do I speed it up?
I have a database table that having close to 100 columns - 25 columns are STRING, the rest is INT/DECIMAL/BOOL. This is the query that I am trying to run - the query is generated based on the search criteria…
mysql5.7 order by id desc limit n ;Optimizer selects primary key index
CREATE TABLE `test` ( `id` bigint UNSIGNED NOT NULL AUTO_INCREMENT, `month` timestamp NOT NULL DEFAULT '2018-01-01 00:00:00', `b` varchar(255) NOT NULL DEFAULT '', `c` varchar(255) NOT NULL DEFAULT '', `d` varchar(255) NOT NULL DEFAULT '', `e` varchar(255) NOT NULL DEFAULT…
Mysql – SQL Inner join with where clause works fast with one condition, but not when activeFlag is added
I have a query like select C.customerId, C.firstName, C.LastName, R.IsActive from Customer as C Inner join Rider as R ON R.customerId = C.customerid where R.rideid = 'xyz' and R.rideareacode = 'abc' and R.isActive = 1 This is taking too much…
How to Optimize Search Queries on a Large PostgreSQL Table without Compound Indexes?
I have a PostgreSQL table named users which contains between 20 to 30 million records. The table has the following columns: id, tenant_id, name, company, location, and description. I need to perform generic search queries on this table with various…