denormalize item sats, comment sats, last comment time, and num comments

prisma/migrations/20220831205352_item_and_comment_stats/migration.sql

@@ -0,0 +1,86 @@
+-- AlterTable
+ALTER TABLE "Item"
+ADD COLUMN IF NOT EXISTS    "commentSats" INTEGER NOT NULL DEFAULT 0,
+ADD COLUMN IF NOT EXISTS    "lastCommentAt" TIMESTAMP(3),
+ADD COLUMN IF NOT EXISTS    "ncomments" INTEGER NOT NULL DEFAULT 0,
+ADD COLUMN IF NOT EXISTS    "sats" INTEGER NOT NULL DEFAULT 0;
+
+-- denormalize all existing comments
+-- for every item, compute the lastest comment time and number of comments
+UPDATE "Item"
+SET "lastCommentAt" = subquery."lastCommentAt", ncomments = subquery.ncomments
+FROM (
+    SELECT a.id, MAX(b.created_at) AS "lastCommentAt", COUNT(b.id) AS ncomments
+    FROM "Item" a
+    LEFT JOIN "Item" b ON b.path <@ a.path AND a.id <> b.id
+    GROUP BY a.id) subquery
+WHERE "Item".id = subquery.id;
+
+-- on comment denormalize comment count and time
+CREATE OR REPLACE FUNCTION ncomments_after_comment() RETURNS TRIGGER AS $$
+DECLARE
+BEGIN
+    UPDATE "Item"
+    SET "lastCommentAt" = now_utc(), "ncomments" = "ncomments" + 1
+    WHERE id <> NEW.id and path @> NEW.path;
+
+    RETURN NEW;
+END;
+$$ LANGUAGE plpgsql;
+
+DROP TRIGGER IF EXISTS ncomments_after_comment_trigger ON "Item";
+CREATE TRIGGER ncomments_after_comment_trigger
+    AFTER INSERT ON "Item"
+    FOR EACH ROW
+    EXECUTE PROCEDURE ncomments_after_comment();
+
+-- denormalize all existing sats
+-- for every item, compute the total sats it has earned
+UPDATE "Item"
+SET sats = subquery.sats
+FROM (
+    SELECT a.id, SUM(c.sats) AS sats
+    FROM "Item" a
+    JOIN "ItemAct" c ON c."itemId" = a.id AND c."userId" <> a."userId"
+    WHERE c.act IN ('VOTE', 'TIP')
+    GROUP BY a.id) subquery
+WHERE "Item".id = subquery.id;
+
+-- denormalize comment sats
+UPDATE "Item"
+SET "commentSats" = subquery."commentSats"
+FROM (
+    SELECT a.id, SUM(b.sats) AS "commentSats"
+    FROM "Item" a
+    JOIN "Item" b ON b.path <@ a.path AND a.id <> b.id
+    GROUP BY a.id) subquery
+WHERE "Item".id = subquery.id;
+
+-- on item act denormalize sats and comment sats
+CREATE OR REPLACE FUNCTION sats_after_act() RETURNS TRIGGER AS $$
+DECLARE
+    item "Item";
+BEGIN
+    SELECT * FROM "Item" WHERE id = NEW."itemId" INTO item;
+    IF item."userId" = NEW."userId" THEN
+        RETURN NEW;
+    END IF;
+
+    UPDATE "Item"
+    SET "sats" = "sats" + NEW.sats
+    WHERE id = item.id;
+
+    UPDATE "Item"
+    SET "commentSats" = "commentSats" + NEW.sats
+    WHERE id <> item.id and path @> item.path;
+
+    RETURN NEW;
+END;
+$$ LANGUAGE plpgsql;
+
+DROP TRIGGER IF EXISTS sats_after_act_trigger ON "ItemAct";
+CREATE TRIGGER sats_after_act_trigger
+    AFTER INSERT ON "ItemAct"
+    FOR EACH ROW
+    WHEN (NEW.act = 'VOTE' or NEW.act = 'TIP')
+    EXECUTE PROCEDURE sats_after_act();

prisma/schema.prisma

@@ -165,12 +165,20 @@ model Item {
   path        Unsupported("LTREE")?
   pin         Pin?                  @relation(fields: [pinId], references: [id])
   pinId       Int?
-  weightedVotes Float                 @default(0)
   boost       Int                   @default(0)
   uploadId    Int?
   upload      Upload?
   paidImgLink Boolean               @default(false)
 
+  // denormalized self stats
+  weightedVotes Float @default(0)
+  sats          Int   @default(0)
+
+  // denormalized comment stats
+  ncomments     Int       @default(0)
+  commentSats   Int       @default(0)
+  lastCommentAt DateTime?
+
   // if sub is null, this is the main sub
   sub     Sub?    @relation(fields: [subName], references: [name])
   subName String? @db.Citext