feat(cli): setup live-queries by Tobbe · Pull Request #1208 · cedarjs/cedar

Tobbe · 2026-02-16T07:33:31Z

Adds CLI command yarn cedar setup live-queries to configure Postgres LISTEN/NOTIFY-based live query invalidation. Creates database triggers that send notifications on table changes, and a Node.js listener that invalidates live query cache keys.

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greptile-apps · 2026-02-16T07:42:51Z

Greptile Summary

Adds CLI command yarn cedar setup live-queries to configure Postgres LISTEN/NOTIFY-based live query invalidation. Creates database triggers that send notifications on table changes, and a Node.js listener that invalidates live query cache keys.

Key improvements in templates:

Migration template sends only recordId instead of full row data to avoid 8KB payload limit
Listener template uses connectionGeneration pattern to prevent reconnect loops
Event trigger automatically attaches to new tables created after migration

Issues found:

Test project files (test-project/api/src/lib/liveQueriesListener.ts and test-project/api/db/migrations/20260215112230_live_queries_notifications/migration.sql) don't match the improved templates
Test migration sends full row_to_json(NEW/OLD) which can hit payload limits
Test listener lacks reconnect loop prevention and expects record object instead of recordId
Test migration missing event trigger for future tables

Confidence Score: 3/5

Safe to merge but test-project files need updates to match improved templates
The CLI templates are well-designed with fixes for known issues (reconnect loops, payload limits, future table support). However, the test-project implementation files still have the old versions with these issues, creating an inconsistency that will confuse users and doesn't properly demonstrate the feature
Update test-project/api/src/lib/liveQueriesListener.ts and test-project/api/db/migrations/20260215112230_live_queries_notifications/migration.sql to match the improved templates

Important Files Changed

Filename	Overview
packages/cli/src/commands/setup/live-queries/liveQueriesHandler.js	CLI handler for setting up live queries - creates migration, listener file, and wires into GraphQL handler. Well-structured with proper validation and error handling.
packages/cli/src/commands/setup/live-queries/templates/liveQueriesListener.ts.template	Template for Postgres listener with `connectionGeneration` pattern to prevent reconnect loops. Sends only `recordId` for efficient notifications.
packages/cli/src/commands/setup/live-queries/templates/migration.sql.template	Improved template sends only `recordId` instead of full row, includes event trigger to automatically attach triggers to new tables.
test-project/api/src/lib/liveQueriesListener.ts	Test project listener has reconnect loop issue - lacks `connectionGeneration` pattern and expects full `record` object from notifications.
test-project/api/db/migrations/20260215112230_live_queries_notifications/migration.sql	Test project migration still uses `row_to_json` with full record data (can exceed 8000 byte limit), and missing event trigger for new tables.

Sequence Diagram

sequenceDiagram
    participant App as GraphQL Server
    participant Listener as liveQueriesListener
    participant PG as PostgreSQL
    participant Cache as liveQueryStore
    participant Client as GraphQL Client

    App->>Listener: startLiveQueryListener()
    Listener->>PG: LISTEN table_change
    
    Note over Client,App: Client makes @live query
    Client->>App: query @live { posts }
    App->>Cache: Store query result with key
    App-->>Client: Return data + invalidation key
    
    Note over PG: User mutates data
    App->>PG: INSERT/UPDATE/DELETE on table
    PG->>PG: Trigger fires cedar_notify_table_change()
    PG->>PG: pg_notify('table_change', json_build_object(...))
    
    PG-->>Listener: NOTIFY with table + recordId
    Listener->>Listener: Parse notification payload
    Listener->>Listener: Generate invalidation keys
    Listener->>Cache: invalidate(['Query.posts', 'Post:123'])
    Cache-->>Client: SSE update with new data

_{Last reviewed commit: 90ca6fb}

greptile-apps

_{10 files reviewed, 3 comments}

_{Edit Code Review Agent Settings | Greptile}

greptile-apps · 2026-02-16T07:42:55Z

packages/cli/src/commands/setup/live-queries/templates/liveQueriesListener.ts.template

+async function connect() {
+  try {
+    if (client) {
+      await client.end()
+    }
+
+    client = new Client({
+      connectionString: process.env.DATABASE_URL,
+    })
+
+    client.on('notification', async (msg) => {
+      await onNotification(msg.payload)
+    })
+
+    client.on('error', (error) => {
+      logger.error(
+        { error },
+        'Postgres live query listener encountered an error'
+      )
+      reconnect()
+    })
+
+    client.on('end', () => {
+      logger.warn('Postgres live query listener disconnected')
+      reconnect()
+    })


Reconnect loop from intentional client.end()

When connect() is called while a previous client exists, client.end() on line 82 fires the end event on the old client (line 101-104), which calls reconnect(), scheduling another connect() in 5 seconds. The current connect() continues and successfully establishes a new connection — but after 5 seconds the spurious reconnect fires, tears down the new connection, and the cycle repeats.

To fix this, either remove the event listeners from the old client before ending it, or set a flag to suppress reconnection during an intentional reconnect:

Suggested change

async function connect() {

try {

if (client) {

await client.end()

}

client = new Client({

connectionString: process.env.DATABASE_URL,

})

client.on('notification', async (msg) => {

await onNotification(msg.payload)

})

client.on('error', (error) => {

logger.error(

{ error },

'Postgres live query listener encountered an error'

)

reconnect()

})

client.on('end', () => {

logger.warn('Postgres live query listener disconnected')

reconnect()

})

async function connect() {

try {

if (client) {

client.removeAllListeners()

await client.end().catch(() => {})

}

client = new Client({

connectionString: process.env.DATABASE_URL,

})

client.on('notification', async (msg) => {

await onNotification(msg.payload)

})

client.on('error', (error) => {

logger.error(

{ error },

'Postgres live query listener encountered an error'

)

reconnect()

})

client.on('end', () => {

logger.warn('Postgres live query listener disconnected')

reconnect()

})

greptile-apps · 2026-02-16T07:42:56Z

packages/cli/src/commands/setup/live-queries/templates/migration.sql.template

+  PERFORM pg_notify(
+    'table_change',
+    json_build_object(
+      'schema', TG_TABLE_SCHEMA,
+      'table', TG_TABLE_NAME,
+      'operation', TG_OP,
+      'record', record_data
+    )::text
+  );


pg_notify payload can exceed 8000-byte limit

PostgreSQL's NOTIFY payload is limited to ~8000 bytes. row_to_json(NEW) / row_to_json(OLD) serializes the entire row — for tables with large text columns, many columns, or binary data this will exceed the limit. When that happens, pg_notify raises an exception that rolls back the entire transaction, causing the original INSERT/UPDATE/DELETE to fail.

Consider truncating the payload or only sending the fields needed for invalidation (table name, operation, and primary key):

Suggested change

PERFORM pg_notify(

'table_change',

json_build_object(

'schema', TG_TABLE_SCHEMA,

'table', TG_TABLE_NAME,

'operation', TG_OP,

'record', record_data

)::text

);

PERFORM pg_notify(

'table_change',

left(

json_build_object(

'schema', TG_TABLE_SCHEMA,

'table', TG_TABLE_NAME,

'operation', TG_OP,

'record', record_data

)::text,

7999

)

);

Alternatively, you could only include the id field (or the primary key) in record_data instead of the full row, which would keep payloads small and avoid the truncation issue entirely.

@greptileai How can I make it only include the primary key of the record?

Here's how to send only the primary key instead of the full row:

Suggested change

PERFORM pg_notify(

'table_change',

json_build_object(

'schema', TG_TABLE_SCHEMA,

'table', TG_TABLE_NAME,

'operation', TG_OP,

'record', record_data

)::text

);

IF (TG_OP = 'DELETE') THEN

record_data = json_build_object('id', OLD.id);

ELSE

record_data = json_build_object('id', NEW.id);

END IF;

This assumes your primary key column is named id. If your tables use a different primary key column name, replace id with that column name. For composite primary keys, you'd include multiple fields in the json_build_object call (e.g., 'user_id', NEW.user_id, 'order_id', NEW.order_id).

greptile-apps · 2026-02-16T07:42:57Z

packages/cli/src/commands/setup/live-queries/templates/migration.sql.template

+END;
+$$ LANGUAGE plpgsql;
+
+SELECT cedar_attach_notify_triggers();


Triggers only attached for tables existing at migration time

cedar_attach_notify_triggers() is invoked once during migration. Any tables created after this migration runs (e.g., from future Prisma migrations) will not have the notify trigger. Users would need to manually re-run SELECT cedar_attach_notify_triggers(); or re-run the migration.

Consider calling out in the docs / final CLI message that the function needs to be re-invoked after schema changes, or adding a note about this limitation.

Tobbe · 2026-02-16T18:39:08Z

@greptileai please do a full review and update your existing review summary

greptile-apps

_{21 files reviewed, 5 comments}

_{Edit Code Review Agent Settings | Greptile}

greptile-apps · 2026-02-16T18:42:32Z

test-project/api/db/migrations/20260215112230_live_queries_notifications/migration.sql

+    record_data = row_to_json(OLD);
+  ELSE
+    record_data = row_to_json(NEW);


Test project migration uses row_to_json(OLD/NEW) instead of just the id field like the template does. This is inconsistent with the improved template at packages/cli/src/commands/setup/live-queries/templates/migration.sql.template which sends only recordId.

_{Note: If this suggestion doesn't match your team's coding style, reply to this and let me know. I'll remember it for next time!}

greptile-apps · 2026-02-16T18:42:33Z

test-project/api/db/migrations/20260215112230_live_queries_notifications/migration.sql

+END;
+$$ LANGUAGE plpgsql;
+
+SELECT cedar_attach_notify_triggers();


Test project migration is missing the event trigger (cedar_event_on_table_create) that automatically attaches triggers to future tables. The template includes this at line 55-98.

greptile-apps · 2026-02-16T18:42:34Z

test-project/api/src/lib/liveQueriesListener.ts

+async function connect() {
+  try {
+    if (client) {
+      await client.end()
+    }
+
+    client = new Client({
+      connectionString: process.env.DATABASE_URL,
+    })
+
+    client.on('notification', async (msg) => {
+      await onNotification(msg.payload)
+    })
+
+    client.on('error', (error) => {
+      logger.error(
+        { error },
+        'Postgres live query listener encountered an error'
+      )
+      reconnect()
+    })
+
+    client.on('end', () => {
+      logger.warn('Postgres live query listener disconnected')
+      reconnect()
+    })
+
+    await client.connect()
+    await client.query(`LISTEN ${LIVE_QUERY_CHANNEL}`)
+
+    logger.info('Postgres live query listener connected')
+  } catch (error) {
+    logger.error({ error }, 'Failed to connect Postgres live query listener')
+    reconnect()


Test project listener lacks the connectionGeneration pattern that prevents reconnect loops. When client.end() is called on line 82, it triggers the end event handler (line 101-104) which calls reconnect(), creating a loop. The template fixes this with a generation counter (see template lines 75-127).

greptile-apps · 2026-02-16T18:42:36Z

test-project/api/src/lib/liveQueriesListener.ts

+interface GetKeysToInvalidateArgs {
+  table: string
+  record: unknown


Interface expects record: unknown but the improved migration template sends recordId: string. This mismatch means the listener won't work correctly with the improved migration template.

greptile-apps · 2026-02-16T18:42:37Z

test-project/api/src/lib/liveQueriesListener.ts

+function getKeysToInvalidate({ table, record }: GetKeysToInvalidateArgs) {
+  const keys = [`Query.${table}`, `Query.${table.toLocaleLowerCase()}`]
+
+  if (isRecordWithId(record)) {
+    keys.push(`${table}:${String(record.id)}`)
+  }
+
+  return keys


Function extracts id from record object, but the improved migration template sends recordId directly as a string. Should accept recordId parameter instead (see template line 15-27).

github-actions · 2026-02-20T03:35:47Z

The changes in this PR are now available in 3.0.0-canary.13430

Adds CLI command `yarn cedar setup live-queries` to configure Postgres LISTEN/NOTIFY-based live query invalidation. Creates database triggers that send notifications on table changes, and a Node.js listener that invalidates live query cache keys.

Tobbe added 8 commits February 13, 2026 15:51

feat(cli): setup live-queries

e966b7b

test-project: Set up realtime

6669219

handler code style

cab11cb

Use getMigrationsPath

2067dc2

handler code style

3abe6af

Update listener template

eacd2bd

lowercase key

d271991

Assert postgres

2745d65

github-actions bot added this to the next-release milestone Feb 16, 2026

greptile-apps bot reviewed Feb 16, 2026

View reviewed changes

Tobbe added 4 commits February 16, 2026 10:20

test-project updates

32c5731

More robust listener

3e95e76

only include id in notification payload

68cd410

Attach event listeners also to future tables

90ca6fb

greptile-apps bot reviewed Feb 16, 2026

View reviewed changes

Tobbe added 5 commits February 16, 2026 12:45

revert test-project changes

002ea19

Merge branch 'main' into tobbe-reat-live-query-setup

da59454

Fix review comments

24f2c31

update --force handling

85c19e4

Merge branch 'main' into tobbe-reat-live-query-setup

8ef80a5

Tobbe enabled auto-merge (squash) February 20, 2026 03:19

Tobbe merged commit d5786d9 into main Feb 20, 2026
42 checks passed

Tobbe deleted the tobbe-reat-live-query-setup branch February 20, 2026 03:27

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Greptile Summary

Confidence Score: 3/5

Important Files Changed

Sequence Diagram

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