From a514726225d9e8f7c07f7d8ba631dc5c4c6dcd5d Mon Sep 17 00:00:00 2001
From: Jakub Riedl <email@jakubriedl.cz>
Date: Tue, 13 May 2025 18:49:27 +1000
Subject: [PATCH] Implement partial autoload in postgres-persister

---
 src/persisters/common/database/postgresql.ts | 94 +++++++++++++++++++-
 1 file changed, 90 insertions(+), 4 deletions(-)

diff --git a/src/persisters/common/database/postgresql.ts b/src/persisters/common/database/postgresql.ts
index ca9052bdc9..0ac84a663d 100644
--- a/src/persisters/common/database/postgresql.ts
+++ b/src/persisters/common/database/postgresql.ts
@@ -2,11 +2,13 @@ import type {
   DatabaseChangeListener,
   DatabaseExecuteCommand,
   DatabasePersisterConfig,
+  PersistedChanges,
   PersistedStore,
   Persister,
   PersisterListener,
   Persists,
 } from '../../../@types/persisters/index.d.ts';
+import type {Changes} from '../../../@types/store/index.d.ts';
 import {arrayJoin, arrayMap} from '../../../common/array.ts';
 import {collHas, collValues} from '../../../common/coll.ts';
 import {getHash} from '../../../common/hash.ts';
@@ -16,6 +18,7 @@ import {
   jsonStringWithUndefined,
 } from '../../../common/json.ts';
 import {mapGet} from '../../../common/map.ts';
+import {objDel, objMap} from '../../../common/obj.ts';
 import {ifNotUndefined, promiseAll} from '../../../common/other.ts';
 import {
   EMPTY_STRING,
@@ -27,6 +30,7 @@ import {
 import {
   CREATE,
   CREATE_TABLE,
+  DEFAULT_ROW_ID_COLUMN_NAME,
   DELETE,
   FUNCTION,
   INSERT,
@@ -46,7 +50,8 @@ import {createTabularPersister} from './tabular.ts';
 
 const TABLE_CREATED = 'c';
 const DATA_CHANGED = 'd';
-const EVENT_REGEX = /^([cd]:)(.+)/;
+const CHANGES_PAYLOAD_JSON = `json_build_object('NEW',NEW,'OLD',OLD)::text`;
+const EVENT_REGEX = /^([cd]:)(.+?)(?::(.+))?$/;
 
 export const createCustomPostgreSqlPersister = <
   ListenerHandle,
@@ -133,6 +138,85 @@ export const createCustomPostgreSqlPersister = <
             newOrOldOrBoth == 0 ? 'NEW' : 'OLD',
           );
 
+  const detectChanges = (
+    tableName: string,
+    payload: string | undefined,
+  ): Changes | undefined => {
+    // trigger isn't row change but table change we want to trigger full reload
+    if (!payload) return undefined;
+    // with JSON mode we can always trigger full reload as it's always referring to single row anyways
+    if (isJson) return undefined;
+
+    const {NEW, OLD} = JSON.parse(payload) as {
+      NEW: Record<string, any> | undefined | null;
+      OLD: Record<string, any> | undefined | null;
+    };
+
+    const tabularLoadConfig = defaultedConfig[0];
+    const valuesConfig = defaultedConfig[2];
+    const shouldLoadValues =
+      typeof valuesConfig === 'string' ? true : valuesConfig[0];
+    const valuesTableName =
+      typeof valuesConfig === 'string' ? valuesConfig : valuesConfig[2];
+
+    if (shouldLoadValues && tableName === valuesTableName) {
+      return [
+        {},
+        objMap(objDel(NEW ?? OLD ?? {}, DEFAULT_ROW_ID_COLUMN_NAME), (field) =>
+          jsonParse(field as string),
+        ),
+        1,
+      ];
+    }
+    if (!managedTableNamesSet.has(tableName) || !tabularLoadConfig) {
+      return undefined;
+    }
+
+    const rowIdColumnName =
+      typeof tabularLoadConfig === 'string'
+        ? DEFAULT_ROW_ID_COLUMN_NAME
+        : (tabularLoadConfig.get(tableName)?.[1] ?? DEFAULT_ROW_ID_COLUMN_NAME);
+
+    const tableId =
+      typeof tabularLoadConfig === 'string'
+        ? tabularLoadConfig
+        : (tabularLoadConfig.get(tableName)?.[0] ?? tableName);
+
+    // row delete
+    if (!NEW && OLD) {
+      const rowId = OLD[rowIdColumnName];
+      return [{[tableId]: {[rowId]: undefined}}, {}, 1];
+    }
+
+    // row insert
+    if (NEW && !OLD) {
+      const rowId = NEW[rowIdColumnName];
+      const row = objMap(objDel(NEW, rowIdColumnName), (field) =>
+        jsonParse(field as string),
+      );
+      return [{[tableId]: {[rowId]: row}}, {}, 1];
+    }
+
+    // row update
+    if (NEW && OLD) {
+      const rowId = NEW[rowIdColumnName];
+      const changedCells: Record<string, any> = {};
+      let hasChanged = false;
+
+      for (const key in NEW) {
+        if (NEW[key] !== OLD[key] && key !== rowIdColumnName) {
+          changedCells[key] = jsonParse(NEW[key]);
+          hasChanged = true;
+        }
+      }
+
+      if (!hasChanged) return undefined;
+      return [{[tableId]: {[rowId]: changedCells}}, {}, 1];
+    }
+
+    return undefined;
+  };
+
   const addDataChangedTriggers = (
     tableName: string,
     dataChangedFunction: string,
@@ -171,7 +255,8 @@ export const createCustomPostgreSqlPersister = <
 
     const dataChangedFunctionName = await createFunction(
       DATA_CHANGED,
-      notify(`'d:'||TG_TABLE_NAME`) + `RETURN NULL;`,
+      notify(`'d:'||TG_TABLE_NAME||':'||${CHANGES_PAYLOAD_JSON}`) +
+        `RETURN NULL;`,
     );
 
     await promiseAll(
@@ -189,7 +274,7 @@ export const createCustomPostgreSqlPersister = <
       (prefixAndTableName) =>
         ifNotUndefined(
           strMatch(prefixAndTableName, EVENT_REGEX),
-          async ([, eventType, tableName]) => {
+          async ([, eventType, tableName, payload]) => {
             if (collHas(managedTableNamesSet, tableName)) {
               if (eventType == 'c:') {
                 await addDataChangedTriggers(
@@ -197,7 +282,8 @@ export const createCustomPostgreSqlPersister = <
                   dataChangedFunctionName,
                 );
               }
-              listener();
+              const changes = detectChanges(tableName, payload);
+              listener(undefined, changes as PersistedChanges<Persist, false>);
             }
           },
         ),