From faa128400f1dd2ff4a8348433c6b7620074e89e9 Mon Sep 17 00:00:00 2001
From: Bel LaPointe <153096461+breel-render@users.noreply.github.com>
Date: Wed, 10 Dec 2025 12:29:32 -0700
Subject: [PATCH] my example was not good tbh

---
 cmd/pg-pubsub-demo/README.md |   1 +
 cmd/pg-pubsub-demo/main.go   | 162 +++++++++++++++++++++++++++++++++++
 2 files changed, 163 insertions(+)
 create mode 100644 cmd/pg-pubsub-demo/README.md
 create mode 100644 cmd/pg-pubsub-demo/main.go

diff --git a/cmd/pg-pubsub-demo/README.md b/cmd/pg-pubsub-demo/README.md
new file mode 100644
index 0000000..d434b6a
--- /dev/null
+++ b/cmd/pg-pubsub-demo/README.md
@@ -0,0 +1 @@
+https://topicpartition.io/blog/postgres-pubsub-queue-benchmarks
\ No newline at end of file
diff --git a/cmd/pg-pubsub-demo/main.go b/cmd/pg-pubsub-demo/main.go
new file mode 100644
index 0000000..d1782a8
--- /dev/null
+++ b/cmd/pg-pubsub-demo/main.go
@@ -0,0 +1,162 @@
+package main
+
+import (
+	"context"
+	"database/sql"
+	"encoding/json"
+	"flag"
+	"fmt"
+	"log"
+	"math/rand"
+	"os"
+	"strconv"
+	"time"
+
+	"pg/src/with"
+
+	_ "github.com/lib/pq"
+)
+
+func main() {
+	if err := with.Context(run); err != nil {
+		panic(err)
+	}
+}
+
+func run(ctx context.Context) error {
+	fs := flag.NewFlagSet(os.Args[0], flag.ContinueOnError)
+	c := fs.String("c", "postgresql://pulsegres:pulsegres@localhost:15432", "conn string")
+	if err := fs.Parse(os.Args[1:]); err != nil {
+		panic(err)
+	}
+
+	return with.PSQL(ctx, *c, func(pg *sql.DB) error {
+		log.Println("creating tables...")
+		for _, sql := range []string{
+			`CREATE SCHEMA IF NOT EXISTS "pubsub"`,
+
+			`CREATE TABLE IF NOT EXISTS "pubsub"."topic_a" (
+				partition INT PRIMARY KEY,
+				partition_offset BIGINT NOT NULL DEFAULT 0
+			)`,
+			`CREATE TABLE IF NOT EXISTS "pubsub"."topic_a_partition_0" (
+				id UUID NOT NULL DEFAULT GEN_RANDOM_UUID() PRIMARY KEY,
+				partition_offset BIGINT UNIQUE NOT NULL,
+				payload BYTEA NOT NULL,
+				created_at TIMESTAMP NOT NULL DEFAULT NOW()
+			)`,
+			`CREATE TABLE IF NOT EXISTS "pubsub"."topic_a_partition_1" (
+				id UUID NOT NULL DEFAULT GEN_RANDOM_UUID() PRIMARY KEY,
+				partition_offset BIGINT UNIQUE NOT NULL,
+				payload BYTEA NOT NULL,
+				created_at TIMESTAMP NOT NULL DEFAULT NOW()
+			)`,
+
+			`INSERT INTO "pubsub"."topic_a" (partition, partition_offset) VALUES (0, 0) ON CONFLICT DO NOTHING`,
+			`INSERT INTO "pubsub"."topic_a" (partition, partition_offset) VALUES (1, 0) ON CONFLICT DO NOTHING`,
+
+			`CREATE TABLE IF NOT EXISTS "pubsub"."consumer_partition_offset" (
+				consumer_group TEXT NOT NULL,
+				partition INT REFERENCES "pubsub"."topic_a"("partition"),
+				partition_offset BIGINT NOT NULL DEFAULT 0,
+				PRIMARY KEY (consumer_group, partition)
+			)`,
+		} {
+			if _, err := pg.ExecContext(ctx, sql); err != nil {
+				return fmt.Errorf("failed setup sql %s: %w", sql, err)
+			}
+		}
+
+		pub := func(a any) error {
+			b, _ := json.Marshal(a)
+			partition := rand.Int() % 2
+			partitionS := strconv.Itoa(partition)
+			_, err := pg.ExecContext(ctx, `
+				WITH reserve AS (
+					UPDATE "pubsub"."topic_a"
+					SET partition_offset=partition_offset+1
+					WHERE partition=`+partitionS+`
+					RETURNING (partition_offset-1) AS offset
+				)
+				INSERT INTO "pubsub"."topic_a_partition_`+partitionS+`" (partition_offset, payload)
+				SELECT reserve.offset, $1 FROM reserve
+			`, b)
+			return err
+		}
+		sub := func(group string) (any, error) {
+			partition := rand.Int() % 2
+			partitionS := strconv.Itoa(partition)
+
+			if _, err := pg.ExecContext(ctx, `
+				INSERT INTO
+				"pubsub"."consumer_partition_offset"
+				(consumer_group, partition)
+				VALUES
+				($1, $2)
+				ON CONFLICT DO NOTHING
+			`, group, partition); err != nil {
+				return nil, err
+			}
+
+			row := pg.QueryRowContext(ctx, `
+				WITH tip AS (
+					SELECT partition_offset-1
+					FROM "pubsub"."topic_a"
+					WHERE partition=`+partitionS+`
+				)
+				, to_claim AS (
+					SELECT partition_offset
+					FROM "pubsub"."consumer_partition_offset"
+					WHERE consumer_group=$1 AND partition=$2
+					FOR UPDATE SKIP LOCKED
+				)
+				, claimed AS (
+					UPDATE "pubsub"."consumer_partition_offset" consumer_partition_offset
+					SET consumer_partition_offset.partition_offset=to_claim.partition_offset+1
+					FROM to_claim
+					WHERE consumer_partition_offset.consumer_group=$1 AND consumer_partition_offset.partition=$2
+					RETURNING consumer_partition_offset.partition_offset
+				)
+				SELECT partition_offset FROM claimed
+			`, group, partition)
+			if err := row.Err(); err != nil {
+				return nil, err
+			}
+
+			var result any
+			if err := row.Scan(&result); err != nil {
+				return nil, err
+			}
+
+			return result, row.Err()
+		}
+
+		go with.Every(ctx, time.Second, func() {
+			for i := 0; i < 2; i++ {
+				if err := pub(1); err != nil {
+					log.Printf("failed pub: %v", err)
+				} else {
+					log.Printf("pubbed")
+				}
+			}
+		})
+
+		with.Every(ctx, time.Second, func() {
+			if err := func() error {
+				for i := 0; i < 2; i++ {
+					group := fmt.Sprintf("group_%d", i)
+					if v, err := sub(group); err != nil {
+						return err
+					} else {
+						log.Printf("%s => %v", group, v)
+					}
+				}
+				return nil
+			}(); err != nil {
+				log.Printf("failed subs: %v", err)
+			}
+		})
+
+		return ctx.Err()
+	})
+}