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POMysql query optimization
 

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    <p>I am working on a Rails project and hitting a performance problem. Here is the simplified db schema</p> <pre> table gaming_platforms ( ~5 rows) id table games ( ~10k rows) id gaming_platform_id winner (black or white or n/a) black_id => online_players.id white_id => online_players.id table online_players ( ~1k rows) id gaming_platform_id username </pre> <p>Now given a username, I want to display players whose names match the input, with no. of games they played, won or lost. </p> <p>I created 3 views to avoid 1+n problem. </p> <pre> create or replace view online_player_games as select online_players.id as online_player_id, count(*) as games from games left join online_players on games.gaming_platform_id = online_players.gaming_platform_id and (games.black_id = online_players.id or games.white_id = online_players.id) group by online_players.id; create or replace view online_player_won_games as select online_players.id as online_player_id, count(games.id) as games from online_players left join games on games.gaming_platform_id = online_players.gaming_platform_id and ((games.winner = 1 and games.black_id = online_players.id) or (games.winner = 2 and games.white_id = online_players.id)) group by online_players.id; create or replace view online_player_lost_games as select online_players.id as online_player_id, count(games.id) as games from online_players left join games on games.gaming_platform_id = online_players.gaming_platform_id and ((games.winner = 2 and games.black_id = online_players.id) or (games.winner = 1 and games.white_id = online_players.id)) group by online_players.id; </pre> <p>Without using any index, it takes > 20 secs to query against those views. The query looks complicated. I am not sure which indexes I should create. Any opinions or suggestions are very welcome.</p>
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    1. USSimone Carletti
    1. USGuoliang Cao
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