From 93cc9276ead4d6745d19224cac45c7ad8642fc33 Mon Sep 17 00:00:00 2001 From: Alan Guo Xiang Tan Date: Thu, 3 Aug 2023 11:51:32 +0800 Subject: [PATCH] PERF: Improve performance of queries when loading a topic list (#22949) (#22950) What is the context of this change? Before 7c6a8f1c74ea7ea3e81d9ffa80ca2227ee36a006, we were using `preload(:tags)` on the topics relation but that was accidentally removed in the refactor. This was discovered and fixed in 5bec894a8c64eb54e349b1570cf76bc03efe3a3d but insteadl of using `preload(:tags)` we ended up using `includes(:tags)`. The problem here is that `includes(:tags)` can either result in `preload(:tags)` or `eager_load(:tags)` but for some reason ActiveRecord is deciding to `eager_load(:tags)` resulting in a joins to the `topic_tags` and `tags` table which is not necessarily and leads to more inefficient queries. When `includes(:tags)` is used, listing the latest topics ended up generating the following sample queries to fetch the list of topics to display. ``` SELECT DISTINCT "topics"."pinned_at" AS alias_0, "topics"."id" FROM "topics" LEFT OUTER JOIN "categories" ON "categories"."id" = "topics"."category_id" LEFT OUTER JOIN "topic_tags" ON "topic_tags"."topic_id" = "topics"."id" LEFT OUTER JOIN "tags" ON "tags"."id" = "topic_tags"."tag_id" LEFT OUTER JOIN topic_users AS tu ON (topics.id = tu.topic_id AND tu.user_id = 29) LEFT JOIN category_users ON category_users.category_id = topics.category_id AND category_users.user_id = 29 WHERE "topics"."deleted_at" IS NULL AND (topics.archetype <> 'private_message') AND (COALESCE(categories.topic_id, 0) <> topics.id) AND (COALESCE(tu.notification_level,1) > 0) AND (topics.category_id = -1 OR (COALESCE(category_users.notification_level, 1) <> 0 AND (topics.category_id IS NULL OR topics.category_id NOT IN(-1))) OR tu.notification_level > 1) AND (pinned_globally AND pinned_at IS NOT NULL AND (topics.pinned_at > tu.cleared_pinned_at OR tu.cleared_pinned_at IS NULL)) ORDER BY "topics"."pinned_at" DESC LIMIT 30 SELECT "topics"."id" AS t0_r0, "topics"."title" AS t0_r1, "topics"."last_posted_at" AS t0_r2, "topics"."created_at" AS t0_r3, "topics"."updated_at" AS t0_r4, "topics"."views" AS t0_r5, "topics"."posts_count" AS t0_r6, "topics"."user_id" AS t0_r7, "topics"."last_post_user_id" AS t0_r8, "topics"."reply_count" AS t0_r9, "topics"."featured_user1_id" AS t0_r10, "topics"."featured_user2_id" AS t0_r11, "topics"."featured_user3_id" AS t0_r12, "topics"."deleted_at" AS t0_r13, "topics"."highest_post_number" AS t0_r14, "topics"."like_count" AS t0_r15, "topics"."incoming_link_count" AS t0_r16, "topics"."category_id" AS t0_r17, "topics"."visible" AS t0_r18, "topics"."moderator_posts_count" AS t0_r19, "topics"."closed" AS t0_r20, "topics"."archived" AS t0_r21, "topics"."bumped_at" AS t0_r22, "topics"."has_summary" AS t0_r23, "topics"."archetype" AS t0_r24, "topics"."featured_user4_id" AS t0_r25, "topics"."notify_moderators_count" AS t0_r26, "topics"."spam_count" AS t0_r27, "topics"."pinned_at" AS t0_r28, "topics"."score" AS t0_r29, "topics"."percent_rank" AS t0_r30, "topics"."subtype" AS t0_r31, "topics"."slug" AS t0_r32, "topics"."deleted_by_id" AS t0_r33, "topics"."participant_count" AS t0_r34, "topics"."word_count" AS t0_r35, "topics"."excerpt" AS t0_r36, "topics"."pinned_globally" AS t0_r37, "topics"."pinned_until" AS t0_r38, "topics"."fancy_title" AS t0_r39, "topics"."highest_staff_post_number" AS t0_r40, "topics"."featured_link" AS t0_r41, "topics"."reviewable_score" AS t0_r42, "topics"."image_upload_id" AS t0_r43, "topics"."slow_mode_seconds" AS t0_r44, "topics"."bannered_until" AS t0_r45, "topics"."external_id" AS t0_r46, "categories"."id" AS t1_r0, "categories"."name" AS t1_r1, "categories"."color" AS t1_r2, "categories"."topic_id" AS t1_r3, "categories"."topic_count" AS t1_r4, "categories"."created_at" AS t1_r5, "categories"."updated_at" AS t1_r6, "categories"."user_id" AS t1_r7, "categories"."topics_year" AS t1_r8, "categories"."topics_month" AS t1_r9, "categories"."topics_week" AS t1_r10, "categories"."slug" AS t1_r11, "categories"."description" AS t1_r12, "categories"."text_color" AS t1_r13, "categories"."read_restricted" AS t1_r14, "categories"."auto_close_hours" AS t1_r15, "categories"."post_count" AS t1_r16, "categories"."latest_post_id" AS t1_r17, "categories"."latest_topic_id" AS t1_r18, "categories"."position" AS t1_r19, "categories"."parent_category_id" AS t1_r20, "categories"."posts_year" AS t1_r21, "categories"."posts_month" AS t1_r22, "categories"."posts_week" AS t1_r23, "categories"."email_in" AS t1_r24, "categories"."email_in_allow_strangers" AS t1_r25, "categories"."topics_day" AS t1_r26, "categories"."posts_day" AS t1_r27, "categories"."allow_badges" AS t1_r28, "categories"."name_lower" AS t1_r29, "categories"."auto_close_based_on_last_post" AS t1_r30, "categories"."topic_template" AS t1_r31, "categories"."contains_messages" AS t1_r32, "categories"."sort_order" AS t1_r33, "categories"."sort_ascending" AS t1_r34, "categories"."uploaded_logo_id" AS t1_r35, "categories"."uploaded_background_id" AS t1_r36, "categories"."topic_featured_link_allowed" AS t1_r37, "categories"."all_topics_wiki" AS t1_r38, "categories"."show_subcategory_list" AS t1_r39, "categories"."num_featured_topics" AS t1_r40, "categories"."default_view" AS t1_r41, "categories"."subcategory_list_style" AS t1_r42, "categories"."default_top_period" AS t1_r43, "categories"."mailinglist_mirror" AS t1_r44, "categories"."minimum_required_tags" AS t1_r45, "categories"."navigate_to_first_post_after_read" AS t1_r46, "categories"."search_priority" AS t1_r47, "categories"."allow_global_tags" AS t1_r48, "categories"."reviewable_by_group_id" AS t1_r49, "categories"."read_only_banner" AS t1_r50, "categories"."default_list_filter" AS t1_r51, "categories"."allow_unlimited_owner_edits_on_first_post" AS t1_r52, "categories"."default_slow_mode_seconds" AS t1_r53, "categories"."uploaded_logo_dark_id" AS t1_r54, "tags"."id" AS t2_r0, "tags"."name" AS t2_r1, "tags"."created_at" AS t2_r2, "tags"."updated_at" AS t2_r3, "tags"."pm_topic_count" AS t2_r4, "tags"."target_tag_id" AS t2_r5, "tags"."description" AS t2_r6, "tags"."public_topic_count" AS t2_r7, "tags"."staff_topic_count" AS t2_r8 FROM "topics" LEFT OUTER JOIN "categories" ON "categories"."id" = "topics"."category_id" LEFT OUTER JOIN "topic_tags" ON "topic_tags"."topic_id" = "topics"."id" LEFT OUTER JOIN "tags" ON "tags"."id" = "topic_tags"."tag_id" LEFT OUTER JOIN topic_users AS tu ON (topics.id = tu.topic_id AND tu.user_id = 29) LEFT JOIN category_users ON category_users.category_id = topics.category_id AND category_users.user_id = 29 WHERE "topics"."deleted_at" IS NULL AND (topics.archetype <> 'private_message') AND (COALESCE(categories.topic_id, 0) <> topics.id) AND (COALESCE(tu.notification_level,1) > 0) AND (topics.category_id = -1 OR (COALESCE(category_users.notification_level, 1) <> 0 AND (topics.category_id IS NULL OR topics.category_id NOT IN(-1))) OR tu.notification_level > 1) AND (pinned_globally AND pinned_at IS NOT NULL AND (topics.pinned_at > tu.cleared_pinned_at OR tu.cleared_pinned_at IS NULL)) AND "topics"."id" = 7 ORDER BY "topics"."pinned_at" DESC SELECT DISTINCT topics.bumped_at AS alias_0, "topics"."id" FROM "topics" LEFT OUTER JOIN "categories" ON "categories"."id" = "topics"."category_id" LEFT OUTER JOIN "topic_tags" ON "topic_tags"."topic_id" = "topics"."id" LEFT OUTER JOIN "tags" ON "tags"."id" = "topic_tags"."tag_id" LEFT OUTER JOIN topic_users AS tu ON (topics.id = tu.topic_id AND tu.user_id = 29) LEFT JOIN category_users ON category_users.category_id = topics.category_id AND category_users.user_id = 29 WHERE "topics"."deleted_at" IS NULL AND (topics.archetype <> 'private_message') AND (COALESCE(categories.topic_id, 0) <> topics.id) AND (COALESCE(tu.notification_level,1) > 0) AND (topics.category_id = -1 OR (COALESCE(category_users.notification_level, 1) <> 0 AND (topics.category_id IS NULL OR topics.category_id NOT IN(-1))) OR tu.notification_level > 1) AND (NOT ( pinned_globally AND pinned_at IS NOT NULL AND (topics.pinned_at > tu.cleared_pinned_at OR tu.cleared_pinned_at IS NULL) )) ORDER BY topics.bumped_at DESC LIMIT 30 SELECT "topics"."id" AS t0_r0, "topics"."title" AS t0_r1, "topics"."last_posted_at" AS t0_r2, "topics"."created_at" AS t0_r3, "topics"."updated_at" AS t0_r4, "topics"."views" AS t0_r5, "topics"."posts_count" AS t0_r6, "topics"."user_id" AS t0_r7, "topics"."last_post_user_id" AS t0_r8, "topics"."reply_count" AS t0_r9, "topics"."featured_user1_id" AS t0_r10, "topics"."featured_user2_id" AS t0_r11, "topics"."featured_user3_id" AS t0_r12, "topics"."deleted_at" AS t0_r13, "topics"."highest_post_number" AS t0_r14, "topics"."like_count" AS t0_r15, "topics"."incoming_link_count" AS t0_r16, "topics"."category_id" AS t0_r17, "topics"."visible" AS t0_r18, "topics"."moderator_posts_count" AS t0_r19, "topics"."closed" AS t0_r20, "topics"."archived" AS t0_r21, "topics"."bumped_at" AS t0_r22, "topics"."has_summary" AS t0_r23, "topics"."archetype" AS t0_r24, "topics"."featured_user4_id" AS t0_r25, "topics"."notify_moderators_count" AS t0_r26, "topics"."spam_count" AS t0_r27, "topics"."pinned_at" AS t0_r28, "topics"."score" AS t0_r29, "topics"."percent_rank" AS t0_r30, "topics"."subtype" AS t0_r31, "topics"."slug" AS t0_r32, "topics"."deleted_by_id" AS t0_r33, "topics"."participant_count" AS t0_r34, "topics"."word_count" AS t0_r35, "topics"."excerpt" AS t0_r36, "topics"."pinned_globally" AS t0_r37, "topics"."pinned_until" AS t0_r38, "topics"."fancy_title" AS t0_r39, "topics"."highest_staff_post_number" AS t0_r40, "topics"."featured_link" AS t0_r41, "topics"."reviewable_score" AS t0_r42, "topics"."image_upload_id" AS t0_r43, "topics"."slow_mode_seconds" AS t0_r44, "topics"."bannered_until" AS t0_r45, "topics"."external_id" AS t0_r46, "categories"."id" AS t1_r0, "categories"."name" AS t1_r1, "categories"."color" AS t1_r2, "categories"."topic_id" AS t1_r3, "categories"."topic_count" AS t1_r4, "categories"."created_at" AS t1_r5, "categories"."updated_at" AS t1_r6, "categories"."user_id" AS t1_r7, "categories"."topics_year" AS t1_r8, "categories"."topics_month" AS t1_r9, "categories"."topics_week" AS t1_r10, "categories"."slug" AS t1_r11, "categories"."description" AS t1_r12, "categories"."text_color" AS t1_r13, "categories"."read_restricted" AS t1_r14, "categories"."auto_close_hours" AS t1_r15, "categories"."post_count" AS t1_r16, "categories"."latest_post_id" AS t1_r17, "categories"."latest_topic_id" AS t1_r18, "categories"."position" AS t1_r19, "categories"."parent_category_id" AS t1_r20, "categories"."posts_year" AS t1_r21, "categories"."posts_month" AS t1_r22, "categories"."posts_week" AS t1_r23, "categories"."email_in" AS t1_r24, "categories"."email_in_allow_strangers" AS t1_r25, "categories"."topics_day" AS t1_r26, "categories"."posts_day" AS t1_r27, "categories"."allow_badges" AS t1_r28, "categories"."name_lower" AS t1_r29, "categories"."auto_close_based_on_last_post" AS t1_r30, "categories"."topic_template" AS t1_r31, "categories"."contains_messages" AS t1_r32, "categories"."sort_order" AS t1_r33, "categories"."sort_ascending" AS t1_r34, "categories"."uploaded_logo_id" AS t1_r35, "categories"."uploaded_background_id" AS t1_r36, "categories"."topic_featured_link_allowed" AS t1_r37, "categories"."all_topics_wiki" AS t1_r38, "categories"."show_subcategory_list" AS t1_r39, "categories"."num_featured_topics" AS t1_r40, "categories"."default_view" AS t1_r41, "categories"."subcategory_list_style" AS t1_r42, "categories"."default_top_period" AS t1_r43, "categories"."mailinglist_mirror" AS t1_r44, "categories"."minimum_required_tags" AS t1_r45, "categories"."navigate_to_first_post_after_read" AS t1_r46, "categories"."search_priority" AS t1_r47, "categories"."allow_global_tags" AS t1_r48, "categories"."reviewable_by_group_id" AS t1_r49, "categories"."read_only_banner" AS t1_r50, "categories"."default_list_filter" AS t1_r51, "categories"."allow_unlimited_owner_edits_on_first_post" AS t1_r52, "categories"."default_slow_mode_seconds" AS t1_r53, "categories"."uploaded_logo_dark_id" AS t1_r54, "tags"."id" AS t2_r0, "tags"."name" AS t2_r1, "tags"."created_at" AS t2_r2, "tags"."updated_at" AS t2_r3, "tags"."pm_topic_count" AS t2_r4, "tags"."target_tag_id" AS t2_r5, "tags"."description" AS t2_r6, "tags"."public_topic_count" AS t2_r7, "tags"."staff_topic_count" AS t2_r8 FROM "topics" LEFT OUTER JOIN "categories" ON "categories"."id" = "topics"."category_id" LEFT OUTER JOIN "topic_tags" ON "topic_tags"."topic_id" = "topics"."id" LEFT OUTER JOIN "tags" ON "tags"."id" = "topic_tags"."tag_id" LEFT OUTER JOIN topic_users AS tu ON (topics.id = tu.topic_id AND tu.user_id = 29) LEFT JOIN category_users ON category_users.category_id = topics.category_id AND category_users.user_id = 29 WHERE "topics"."deleted_at" IS NULL AND (topics.archetype <> 'private_message') AND (COALESCE(categories.topic_id, 0) <> topics.id) AND (COALESCE(tu.notification_level,1) > 0) AND (topics.category_id = -1 OR (COALESCE(category_users.notification_level, 1) <> 0 AND (topics.category_id IS NULL OR topics.category_id NOT IN(-1))) OR tu.notification_level > 1) AND (NOT ( pinned_globally AND pinned_at IS NOT NULL AND (topics.pinned_at > tu.cleared_pinned_at OR tu.cleared_pinned_at IS NULL) )) AND "topics"."id" IN (477, 481, 480, 479, 478, 467, 466, 230, 209, 183, 173, 179, 168, 139, 102, 144, 150, 118, 126, 88, 63, 46, 117, 171, 45, 77, 154, 158, 43, 79) ORDER BY topics.bumped_at DESC ``` Note how there are two extra queries which has to select `DISTINCT topics.pinned_at` and `DISTINCT topics.bumped_at` because of the unnecessary left joins to the `topic_tags` and `tags` table result in duplicated rows in the topic tables. As a result, PG is not able to use our indexes to effectively execute the query. Comparing this to the queries being executed when `preload(:tags)` is used. ``` SELECT "topics"."id" AS t0_r0, "topics"."title" AS t0_r1, "topics"."last_posted_at" AS t0_r2, "topics"."created_at" AS t0_r3, "topics"."updated_at" AS t0_r4, "topics"."views" AS t0_r5, "topics"."posts_count" AS t0_r6, "topics"."user_id" AS t0_r7, "topics"."last_post_user_id" AS t0_r8, "topics"."reply_count" AS t0_r9, "topics"."featured_user1_id" AS t0_r10, "topics"."featured_user2_id" AS t0_r11, "topics"."featured_user3_id" AS t0_r12, "topics"."deleted_at" AS t0_r13, "topics"."highest_post_number" AS t0_r14, "topics"."like_count" AS t0_r15, "topics"."incoming_link_count" AS t0_r16, "topics"."category_id" AS t0_r17, "topics"."visible" AS t0_r18, "topics"."moderator_posts_count" AS t0_r19, "topics"."closed" AS t0_r20, "topics"."archived" AS t0_r21, "topics"."bumped_at" AS t0_r22, "topics"."has_summary" AS t0_r23, "topics"."archetype" AS t0_r24, "topics"."featured_user4_id" AS t0_r25, "topics"."notify_moderators_count" AS t0_r26, "topics"."spam_count" AS t0_r27, "topics"."pinned_at" AS t0_r28, "topics"."score" AS t0_r29, "topics"."percent_rank" AS t0_r30, "topics"."subtype" AS t0_r31, "topics"."slug" AS t0_r32, "topics"."deleted_by_id" AS t0_r33, "topics"."participant_count" AS t0_r34, "topics"."word_count" AS t0_r35, "topics"."excerpt" AS t0_r36, "topics"."pinned_globally" AS t0_r37, "topics"."pinned_until" AS t0_r38, "topics"."fancy_title" AS t0_r39, "topics"."highest_staff_post_number" AS t0_r40, "topics"."featured_link" AS t0_r41, "topics"."reviewable_score" AS t0_r42, "topics"."image_upload_id" AS t0_r43, "topics"."slow_mode_seconds" AS t0_r44, "topics"."bannered_until" AS t0_r45, "topics"."external_id" AS t0_r46, "categories"."id" AS t1_r0, "categories"."name" AS t1_r1, "categories"."color" AS t1_r2, "categories"."topic_id" AS t1_r3, "categories"."topic_count" AS t1_r4, "categories"."created_at" AS t1_r5, "categories"."updated_at" AS t1_r6, "categories"."user_id" AS t1_r7, "categories"."topics_year" AS t1_r8, "categories"."topics_month" AS t1_r9, "categories"."topics_week" AS t1_r10, "categories"."slug" AS t1_r11, "categories"."description" AS t1_r12, "categories"."text_color" AS t1_r13, "categories"."read_restricted" AS t1_r14, "categories"."auto_close_hours" AS t1_r15, "categories"."post_count" AS t1_r16, "categories"."latest_post_id" AS t1_r17, "categories"."latest_topic_id" AS t1_r18, "categories"."position" AS t1_r19, "categories"."parent_category_id" AS t1_r20, "categories"."posts_year" AS t1_r21, "categories"."posts_month" AS t1_r22, "categories"."posts_week" AS t1_r23, "categories"."email_in" AS t1_r24, "categories"."email_in_allow_strangers" AS t1_r25, "categories"."topics_day" AS t1_r26, "categories"."posts_day" AS t1_r27, "categories"."allow_badges" AS t1_r28, "categories"."name_lower" AS t1_r29, "categories"."auto_close_based_on_last_post" AS t1_r30, "categories"."topic_template" AS t1_r31, "categories"."contains_messages" AS t1_r32, "categories"."sort_order" AS t1_r33, "categories"."sort_ascending" AS t1_r34, "categories"."uploaded_logo_id" AS t1_r35, "categories"."uploaded_background_id" AS t1_r36, "categories"."topic_featured_link_allowed" AS t1_r37, "categories"."all_topics_wiki" AS t1_r38, "categories"."show_subcategory_list" AS t1_r39, "categories"."num_featured_topics" AS t1_r40, "categories"."default_view" AS t1_r41, "categories"."subcategory_list_style" AS t1_r42, "categories"."default_top_period" AS t1_r43, "categories"."mailinglist_mirror" AS t1_r44, "categories"."minimum_required_tags" AS t1_r45, "categories"."navigate_to_first_post_after_read" AS t1_r46, "categories"."search_priority" AS t1_r47, "categories"."allow_global_tags" AS t1_r48, "categories"."reviewable_by_group_id" AS t1_r49, "categories"."read_only_banner" AS t1_r50, "categories"."default_list_filter" AS t1_r51, "categories"."allow_unlimited_owner_edits_on_first_post" AS t1_r52, "categories"."default_slow_mode_seconds" AS t1_r53, "categories"."uploaded_logo_dark_id" AS t1_r54 FROM "topics" LEFT OUTER JOIN "categories" ON "categories"."id" = "topics"."category_id" LEFT OUTER JOIN topic_users AS tu ON (topics.id = tu.topic_id AND tu.user_id = 29) LEFT JOIN category_users ON category_users.category_id = topics.category_id AND category_users.user_id = 29 WHERE "topics"."deleted_at" IS NULL AND (topics.archetype <> 'private_message') AND (COALESCE(categories.topic_id, 0) <> topics.id) AND (COALESCE(tu.notification_level,1) > 0) AND (topics.category_id = -1 OR (COALESCE(category_users.notification_level, 1) <> 0 AND (topics.category_id IS NULL OR topics.category_id NOT IN(-1))) OR tu.notification_level > 1) AND (pinned_globally AND pinned_at IS NOT NULL AND (topics.pinned_at > tu.cleared_pinned_at OR tu.cleared_pinned_at IS NULL)) ORDER BY "topics"."pinned_at" DESC LIMIT 30 SELECT "topic_tags".* FROM "topic_tags" WHERE "topic_tags"."topic_id" = 7 SELECT "topics"."id" AS t0_r0, "topics"."title" AS t0_r1, "topics"."last_posted_at" AS t0_r2, "topics"."created_at" AS t0_r3, "topics"."updated_at" AS t0_r4, "topics"."views" AS t0_r5, "topics"."posts_count" AS t0_r6, "topics"."user_id" AS t0_r7, "topics"."last_post_user_id" AS t0_r8, "topics"."reply_count" AS t0_r9, "topics"."featured_user1_id" AS t0_r10, "topics"."featured_user2_id" AS t0_r11, "topics"."featured_user3_id" AS t0_r12, "topics"."deleted_at" AS t0_r13, "topics"."highest_post_number" AS t0_r14, "topics"."like_count" AS t0_r15, "topics"."incoming_link_count" AS t0_r16, "topics"."category_id" AS t0_r17, "topics"."visible" AS t0_r18, "topics"."moderator_posts_count" AS t0_r19, "topics"."closed" AS t0_r20, "topics"."archived" AS t0_r21, "topics"."bumped_at" AS t0_r22, "topics"."has_summary" AS t0_r23, "topics"."archetype" AS t0_r24, "topics"."featured_user4_id" AS t0_r25, "topics"."notify_moderators_count" AS t0_r26, "topics"."spam_count" AS t0_r27, "topics"."pinned_at" AS t0_r28, "topics"."score" AS t0_r29, "topics"."percent_rank" AS t0_r30, "topics"."subtype" AS t0_r31, "topics"."slug" AS t0_r32, "topics"."deleted_by_id" AS t0_r33, "topics"."participant_count" AS t0_r34, "topics"."word_count" AS t0_r35, "topics"."excerpt" AS t0_r36, "topics"."pinned_globally" AS t0_r37, "topics"."pinned_until" AS t0_r38, "topics"."fancy_title" AS t0_r39, "topics"."highest_staff_post_number" AS t0_r40, "topics"."featured_link" AS t0_r41, "topics"."reviewable_score" AS t0_r42, "topics"."image_upload_id" AS t0_r43, "topics"."slow_mode_seconds" AS t0_r44, "topics"."bannered_until" AS t0_r45, "topics"."external_id" AS t0_r46, "categories"."id" AS t1_r0, "categories"."name" AS t1_r1, "categories"."color" AS t1_r2, "categories"."topic_id" AS t1_r3, "categories"."topic_count" AS t1_r4, "categories"."created_at" AS t1_r5, "categories"."updated_at" AS t1_r6, "categories"."user_id" AS t1_r7, "categories"."topics_year" AS t1_r8, "categories"."topics_month" AS t1_r9, "categories"."topics_week" AS t1_r10, "categories"."slug" AS t1_r11, "categories"."description" AS t1_r12, "categories"."text_color" AS t1_r13, "categories"."read_restricted" AS t1_r14, "categories"."auto_close_hours" AS t1_r15, "categories"."post_count" AS t1_r16, "categories"."latest_post_id" AS t1_r17, "categories"."latest_topic_id" AS t1_r18, "categories"."position" AS t1_r19, "categories"."parent_category_id" AS t1_r20, "categories"."posts_year" AS t1_r21, "categories"."posts_month" AS t1_r22, "categories"."posts_week" AS t1_r23, "categories"."email_in" AS t1_r24, "categories"."email_in_allow_strangers" AS t1_r25, "categories"."topics_day" AS t1_r26, "categories"."posts_day" AS t1_r27, "categories"."allow_badges" AS t1_r28, "categories"."name_lower" AS t1_r29, "categories"."auto_close_based_on_last_post" AS t1_r30, "categories"."topic_template" AS t1_r31, "categories"."contains_messages" AS t1_r32, "categories"."sort_order" AS t1_r33, "categories"."sort_ascending" AS t1_r34, "categories"."uploaded_logo_id" AS t1_r35, "categories"."uploaded_background_id" AS t1_r36, "categories"."topic_featured_link_allowed" AS t1_r37, "categories"."all_topics_wiki" AS t1_r38, "categories"."show_subcategory_list" AS t1_r39, "categories"."num_featured_topics" AS t1_r40, "categories"."default_view" AS t1_r41, "categories"."subcategory_list_style" AS t1_r42, "categories"."default_top_period" AS t1_r43, "categories"."mailinglist_mirror" AS t1_r44, "categories"."minimum_required_tags" AS t1_r45, "categories"."navigate_to_first_post_after_read" AS t1_r46, "categories"."search_priority" AS t1_r47, "categories"."allow_global_tags" AS t1_r48, "categories"."reviewable_by_group_id" AS t1_r49, "categories"."read_only_banner" AS t1_r50, "categories"."default_list_filter" AS t1_r51, "categories"."allow_unlimited_owner_edits_on_first_post" AS t1_r52, "categories"."default_slow_mode_seconds" AS t1_r53, "categories"."uploaded_logo_dark_id" AS t1_r54 FROM "topics" LEFT OUTER JOIN "categories" ON "categories"."id" = "topics"."category_id" LEFT OUTER JOIN topic_users AS tu ON (topics.id = tu.topic_id AND tu.user_id = 29) LEFT JOIN category_users ON category_users.category_id = topics.category_id AND category_users.user_id = 29 WHERE "topics"."deleted_at" IS NULL AND (topics.archetype <> 'private_message') AND (COALESCE(categories.topic_id, 0) <> topics.id) AND (COALESCE(tu.notification_level,1) > 0) AND (topics.category_id = -1 OR (COALESCE(category_users.notification_level, 1) <> 0 AND (topics.category_id IS NULL OR topics.category_id NOT IN(-1))) OR tu.notification_level > 1) AND (NOT ( pinned_globally AND pinned_at IS NOT NULL AND (topics.pinned_at > tu.cleared_pinned_at OR tu.cleared_pinned_at IS NULL) )) ORDER BY topics.bumped_at DESC LIMIT 30 SELECT "topic_tags".* FROM "topic_tags" WHERE "topic_tags"."topic_id" IN (477, 481, 480, 479, 478, 467, 466, 230, 209, 183, 173, 179, 168, 139, 102, 144, 150, 118, 126, 88, 63, 46, 117, 171, 45, 77, 154, 158, 43, 79) SELECT "tags"."id", "tags"."name", "tags"."created_at", "tags"."updated_at", "tags"."pm_topic_count", "tags"."target_tag_id", "tags"."description", "tags"."public_topic_count", "tags"."staff_topic_count" FROM "tags" WHERE "tags"."id" IN (10, 20, 26, 7, 27, 28, 30, 19, 9, 4, 15, 29, 14, 18, 11, 25, 1, 21, 8, 22, 5, 32) ``` We end up with queries that are much more efficient as those queries can effectively use the indexes. --- lib/topic_query.rb | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/lib/topic_query.rb b/lib/topic_query.rb index 3409f754586..4db4b8d090b 100644 --- a/lib/topic_query.rb +++ b/lib/topic_query.rb @@ -750,7 +750,9 @@ class TopicQuery end if SiteSetting.tagging_enabled - result = result.includes(:tags) + # Use `preload` here instead since `includes` can end up calling `eager_load` which can unnecessarily lead to + # joins on the `topic_tags` and `tags` table leading to a much slower query. + result = result.preload(:tags) result = filter_by_tags(result) end