PostgreSQL: Which is the better index order?

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What index(es) would be most helpful for running many of these PostgreSQL queries?

SELECT id, pair_time, user1, user2 
FROM pairs 
WHERE ? in (user1, user2) 
ORDER by pair_time

? = arbitrary username specified at run time.

I was thinking these two indexes:

CREATE INDEX ON pairs (user1, pair_time)
CREATE INDEX ON pairs (user2, pair_time)

But should the order be reversed?

CREATE INDEX ON pairs (pair_time, user1) 
CREATE INDEX ON pairs (pair_time, user2) 

Is there a better solution requiring just one index?

I do not know if Postgres will use any of those indexes wisely on this query.

You might try this:

SELECT u.*
FROM ((SELECT id, pair_time, user1, user2
       FROM pairs
       WHERE user1 = ?
      ) UNION ALL
      (SELECT id, pair_time, user1, user2
       FROM pairs
       WHERE user2 = ?
      )
     ) u
ORDER by pair_time;

This will use indexes on pairs(user1) and pairs(user2) for each subquery. The outer order by will require sorting the data. I cannot think of a way off-hand to remove the outer sort.

Index Order Does Matter, For example, if a has many duplicate values, and b has mostly unique values, having a at the start of the index is suboptimal — better to use b first, which will more effectively narrow the search space when looking for matches on a. Notice the increasing costs, even though all queries match one indexed row. Of the index types currently supported by PostgreSQL, only B-tree can produce sorted output — the other index types return matching rows in an unspecified, implementation-dependent order. The planner will consider satisfying an ORDER BY specification either by scanning any available index that matches the specification, or by scanning the

Another option would be to use a GIN index an an array of both columns:

create index on pairs using gin ((array[user1, user2]) array_ops);

Then change your query to use compare arrays:

select id, pair_time, user1, user2 
from pairs
where array[user1, user2] && array[1234]
order by pair_time

Efficient Use of PostgreSQL Indexes, I do not know if Postgres will use any of those indexes wisely on this query. You might try this: SELECT u.* FROM ((SELECT id, pair_time, user1� PostgreSQL: Which is the better index order? Ask Question Asked 9 months ago. Active 9 months ago. Viewed 40 times 1. What index(es) would be most helpful for running

I think regarding your below query

SELECT id, pair_time, user1, user2 FROM pairs WHERE ? in (user1, user2) ORDER by pair_time

below index will help better than others 2 index that you create

CREATE INDEX ON user_pairs (user1, pair_time)
CREATE INDEX ON user_pairs (user2, pair_time)

PostgreSQL: Which is the better index order?, Indexes are really important for Postgres performance, but they're an index to a sort order, you want to sort rows by more than one column. For example, an index computed on upper(col) would allow the clause WHERE upper(col) = 'JIM' to use an index. PostgreSQL provides the index methods B-tree, hash, GiST, and GIN. Users can also define their own index methods, but that is fairly complicated. When the WHERE clause is present, a partial index is created. A partial index is an index

Postgres indexes for absolute beginners, posted_at DESC NULLS LAST ) ORDER BY share_count DESC NULLS LAST, You have one more subquery-level than you actually need. with an index on (COALESCE(parent_id, message_id) may perform better. The PostgreSQL ORDER BY clause is used to sort the data in ascending or descending order, based on one or more columns. Syntax. The basic syntax of ORDER BY clause is as follows − SELECT column-list FROM table_name [WHERE condition] [ORDER BY column1, column2, .. columnN] [ASC | DESC]; You can use more than one column in the ORDER BY clause.

how to use index to speed up sorting in postgres, B-tree indexes are Postgres's default, and they can be used for nulls to sort lower than numbers, but the index has them stored as higher than� As you can see we filtered for c, b, a but the optimizer changed the order of those conditions and turned it into a, b, c to make sure that the index we created suits the query. There are some important things to learn here: The order of the conditions in your WHERE clause makes no difference; PostgreSQL will find the right indexes automatically

Using Simple Indexes to Optimize Complicated Sorts in Postgres, As a time-series database built on PostgreSQL, TimescaleDB utilizes the right alongside time-series data, join across tables, and best of all, use SQL. The secret to remember when building indexes is that order matters. PostgreSQL doesn't care at all about the order of entries in a WHERE clause, and chooses indexes and execution order based on cost and selectivity estimation alone. The order in which joins are written is also ignored up to the configured join_collapse_limit ; if there are more joins than that, it'll execute them in the order they're written.