Fix bug with mq_latest_message where the wrong message may be returned

if multiple messages have the exact same creation date.

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "sqlxmq"
-version = "0.3.1"
+version = "0.3.2"
 authors = ["Diggory Blake <[email protected]>"]
 edition = "2018"
 license = "MIT OR Apache-2.0"
@@ -23,7 +23,7 @@ uuid = { version = "0.8.2", features = ["v4"] }
 log = "0.4.14"
 serde_json = "1.0.64"
 serde = "1.0.124"
-sqlxmq_macros = { version = "0.3.1", path = "sqlxmq_macros" }
+sqlxmq_macros = { version = "0.3.2", path = "sqlxmq_macros" }
 anymap2 = "0.13.0"
 
 [features]

migrations/20211013151757_fix_mq_latest_message.down.sql

@@ -0,0 +1,15 @@
+CREATE OR REPLACE FUNCTION mq_latest_message(from_channel_name TEXT, from_channel_args TEXT)
+RETURNS UUID AS $$
+    SELECT COALESCE(
+        (
+            SELECT id FROM mq_msgs
+            WHERE channel_name = from_channel_name
+            AND channel_args = from_channel_args
+            AND after_message_id IS NOT NULL
+            AND id != uuid_nil()
+            ORDER BY created_at DESC, id DESC
+            LIMIT 1
+        ),
+        uuid_nil()
+    )
+$$ LANGUAGE SQL STABLE;

migrations/20211013151757_fix_mq_latest_message.up.sql

@@ -0,0 +1,19 @@
+CREATE OR REPLACE FUNCTION mq_latest_message(from_channel_name TEXT, from_channel_args TEXT)
+RETURNS UUID AS $$
+    SELECT COALESCE(
+        (
+            SELECT id FROM mq_msgs
+            WHERE channel_name = from_channel_name
+            AND channel_args = from_channel_args
+            AND after_message_id IS NOT NULL
+            AND id != uuid_nil()
+            AND NOT EXISTS(
+                SELECT * FROM mq_msgs AS mq_msgs2
+                WHERE mq_msgs2.after_message_id = mq_msgs.id
+            )
+            ORDER BY created_at DESC
+            LIMIT 1
+        ),
+        uuid_nil()
+    )
+$$ LANGUAGE SQL STABLE;

sqlxmq_macros/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "sqlxmq_macros"
-version = "0.3.1"
+version = "0.3.2"
 authors = ["Diggory Blake <[email protected]>"]
 edition = "2018"
 license = "MIT OR Apache-2.0"

sqlxmq_stress/migrations/20211013151757_fix_mq_latest_message.down.sql

@@ -0,0 +1,15 @@
+CREATE OR REPLACE FUNCTION mq_latest_message(from_channel_name TEXT, from_channel_args TEXT)
+RETURNS UUID AS $$
+    SELECT COALESCE(
+        (
+            SELECT id FROM mq_msgs
+            WHERE channel_name = from_channel_name
+            AND channel_args = from_channel_args
+            AND after_message_id IS NOT NULL
+            AND id != uuid_nil()
+            ORDER BY created_at DESC, id DESC
+            LIMIT 1
+        ),
+        uuid_nil()
+    )
+$$ LANGUAGE SQL STABLE;

sqlxmq_stress/migrations/20211013151757_fix_mq_latest_message.up.sql

@@ -0,0 +1,19 @@
+CREATE OR REPLACE FUNCTION mq_latest_message(from_channel_name TEXT, from_channel_args TEXT)
+RETURNS UUID AS $$
+    SELECT COALESCE(
+        (
+            SELECT id FROM mq_msgs
+            WHERE channel_name = from_channel_name
+            AND channel_args = from_channel_args
+            AND after_message_id IS NOT NULL
+            AND id != uuid_nil()
+            AND NOT EXISTS(
+                SELECT * FROM mq_msgs AS mq_msgs2
+                WHERE mq_msgs2.after_message_id = mq_msgs.id
+            )
+            ORDER BY created_at DESC
+            LIMIT 1
+        ),
+        uuid_nil()
+    )
+$$ LANGUAGE SQL STABLE;