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POOptimize difficult query (possibly with squeel)
 

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    <p>There is such code(using PublicActivity gem &amp; Squeel)</p> <pre><code> def index @activities = Activity.limit(20).order { created_at.desc } @one = @activities.where{trackable_type == 'Post'}.includes(trackable: [:author, :project]) @two = @activities.where{trackable_type == 'Project'}.includes trackable: [:owner] @activities = @one + @two end </code></pre> <p>But it creates <strong>8</strong> SQL requests:</p> <pre><code> SELECT "activities".* FROM "activities" WHERE "activities"."trackable_type" = 'Post' ORDER BY "activities"."created_at" DESC LIMIT 20 SELECT "posts".* FROM "posts" WHERE "posts"."id" IN (800, 799, 798, 797, 796, 795, 794, 793, 792, 791, 790, 789, 788, 787, 786, 785, 784, 783, 782, 781) SELECT "users".* FROM "users" WHERE "users"."id" IN (880, 879, 878, 877, 876, 875, 874, 873, 872, 871, 869, 868, 867, 866, 865, 864, 863, 862, 861, 860) SELECT "projects".* FROM "projects" WHERE "projects"."id" IN (80, 79) SELECT "activities".* FROM "activities" WHERE "activities"."trackable_type" = 'Project' ORDER BY "activities"."created_at" DESC LIMIT 20 SELECT "projects".* FROM "projects" WHERE "projects"."id" IN (80, 79, 78, 77, 76, 75, 74, 73, 72, 71, 70, 69, 68, 67, 66, 65, 64, 63, 62, 61) SELECT "users".* FROM "users" WHERE "users"."id" IN (870, 859, 848, 837, 826, 815, 804, 793, 782, 771, 760, 749, 738, 727, 716, 705, 694, 683, 672, 661) </code></pre> <ol> <li>activites request are not joined</li> <li>some users (post owner and project owner) are loaded twice</li> <li>some projects are loaded twice</li> <li>@activities is Array. Rails relations merge methods(except <code>+</code>) don't work with the code above.</li> </ol> <p>Any ideas to optimize it?</p>
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    1. COyou can always execute a raw query in rails. Simply construct the sql string and then you can parse the returned data set on the requesting side ... which will be much faster than doing 8 queries
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    2. CO1) It's not rails-way. 2) I'm not very good with SQL, and don't really know how should query view at the end:)
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    3. COHmmmmmmmmmmm, disagree about it not being the rails way. Anything outside of cookie-cutter queries and you'll have to use a custom where clause anyhow. The helper functions just add a bit of abstraction and portability
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