Fix for count being very slow on large Parse Classes' collections (Postgres) (#5330)

* Changed count to be approximate. Should help with postgres slowness

* refactored last commit to only fall back to estimate if no complex query

* handlign variables correctly

* Trying again because it was casting to lowercase table names which doesnt work for us/

* syntax error

* Adding quotations to pg query

* hopefully final pg fix

* Postgres will now use an approximate count unless there is a more complex query specified

* handling edge case

* Fix for count being very slow on large Parse Classes' collections in Postgres. Replicating fix for Mongo in issue 5264

* Fixed silly spelling error resulting from copying over notes

* Lint fixes

* limiting results to 1 on approximation

* suppress test that we can no longer run for postgres

* removed tests from Postgres that no longer apply

* made changes requested by dplewis

* fixed count errors

* updated package.json

* removed test exclude for pg

* removed object types from method

* test disabled for postgres

* returned type

* add estimate count test

* fix mongo test

spec/InstallationsRouter.spec.js

@@ -160,7 +160,7 @@ describe('InstallationsRouter', () => {
       });
   });
 
-  it('query installations with count = 1', done => {
+  it_exclude_dbs(['postgres'])('query installations with count = 1', done => {
     const config = Config.get('test');
     const androidDeviceRequest = {
       installationId: '12345678-abcd-abcd-abcd-123456789abc',
@@ -209,7 +209,7 @@ describe('InstallationsRouter', () => {
       });
   });
 
-  it('query installations with limit = 0 and count = 1', done => {
+  it_only_db('postgres')('query installations with count = 1', async () => {
     const config = Config.get('test');
     const androidDeviceRequest = {
       installationId: '12345678-abcd-abcd-abcd-123456789abc',
@@ -224,40 +224,90 @@ describe('InstallationsRouter', () => {
       auth: auth.master(config),
       body: {},
       query: {
-        limit: 0,
         count: 1,
       },
       info: {},
     };
 
     const router = new InstallationsRouter();
-    rest
-      .create(
-        config,
-        auth.nobody(config),
-        '_Installation',
-        androidDeviceRequest
-      )
-      .then(() => {
-        return rest.create(
+    await rest.create(
+      config,
+      auth.nobody(config),
+      '_Installation',
+      androidDeviceRequest
+    );
+    await rest.create(
+      config,
+      auth.nobody(config),
+      '_Installation',
+      iosDeviceRequest
+    );
+    let res = await router.handleFind(request);
+    let response = res.response;
+    expect(response.results.length).toEqual(2);
+    expect(response.count).toEqual(0); // estimate count is zero
+
+    const pgAdapter = config.database.adapter;
+    await pgAdapter.updateEstimatedCount('_Installation');
+
+    res = await router.handleFind(request);
+    response = res.response;
+    expect(response.results.length).toEqual(2);
+    expect(response.count).toEqual(2);
+  });
+
+  it_exclude_dbs(['postgres'])(
+    'query installations with limit = 0 and count = 1',
+    done => {
+      const config = Config.get('test');
+      const androidDeviceRequest = {
+        installationId: '12345678-abcd-abcd-abcd-123456789abc',
+        deviceType: 'android',
+      };
+      const iosDeviceRequest = {
+        installationId: '12345678-abcd-abcd-abcd-123456789abd',
+        deviceType: 'ios',
+      };
+      const request = {
+        config: config,
+        auth: auth.master(config),
+        body: {},
+        query: {
+          limit: 0,
+          count: 1,
+        },
+        info: {},
+      };
+
+      const router = new InstallationsRouter();
+      rest
+        .create(
           config,
           auth.nobody(config),
           '_Installation',
-          iosDeviceRequest
-        );
-      })
-      .then(() => {
-        return router.handleFind(request);
-      })
-      .then(res => {
-        const response = res.response;
-        expect(response.results.length).toEqual(0);
-        expect(response.count).toEqual(2);
-        done();
-      })
-      .catch(err => {
-        fail(JSON.stringify(err));
-        done();
-      });
-  });
+          androidDeviceRequest
+        )
+        .then(() => {
+          return rest.create(
+            config,
+            auth.nobody(config),
+            '_Installation',
+            iosDeviceRequest
+          );
+        })
+        .then(() => {
+          return router.handleFind(request);
+        })
+        .then(res => {
+          const response = res.response;
+          expect(response.results.length).toEqual(0);
+          expect(response.count).toEqual(2);
+          done();
+        })
+        .catch(err => {
+          fail(JSON.stringify(err));
+          done();
+        });
+    }
+  );
 });