Add an index and revise a select related to deleting all shots (#3629)

* Remove two seq scans and a sort from a select query. (#3568)
* Add index to column that's used in a WHERE.
* Update db schema.
* Up the DB level.
* Use acct id to get device ids; del img data for all device ids.
* Use device id when there's no account id to delete shots.

server/db-patches/patch-20-21.sql

@@ -0,0 +1 @@
+CREATE INDEX images_shotid_idx ON images (shotid);

server/db-patches/patch-21-20.sql

@@ -0,0 +1 @@
+DROP INDEX images_shotid_idx;

server/schema.sql

@@ -72,6 +72,7 @@ ALTER TABLE ONLY states
     ADD CONSTRAINT states_pkey PRIMARY KEY (state);
 CREATE INDEX data_deviceid_idx ON data USING btree (deviceid);
 CREATE INDEX devices_accountid_idx ON devices USING btree (accountid);
+CREATE INDEX images_shotid_idx ON images USING btree (shotid);
 CREATE INDEX searchable_text_idx ON data USING gin (searchable_text);
 CREATE INDEX states_deviceid_idx ON states USING btree (deviceid);
 ALTER TABLE ONLY data

server/src/dbschema.js

@@ -6,7 +6,7 @@ const mozlog = require("./logging").mozlog("dbschema");
 
 // When updating the database, please also run ./bin/dumpschema --record
 // This updates schema.sql with the latest full database schema
-const MAX_DB_LEVEL = exports.MAX_DB_LEVEL = 20;
+const MAX_DB_LEVEL = exports.MAX_DB_LEVEL = 21;
 
 exports.forceDbVersion = function(version) {
   mozlog.info("forcing-db-version", {db: db.constr, version});

server/src/pages/leave-screenshots/server.js

@@ -23,7 +23,7 @@ app.post("/leave", function(req, res) {
   if (!req.deviceId) {
     res.status(403).send(req.getText("leavePageErrorAddonRequired"));
   }
-  Shot.deleteEverythingForDevice(req.backend, req.deviceId).then(() => {
+  Shot.deleteEverythingForDevice(req.backend, req.deviceId, req.accountId).then(() => {
     res.redirect("/leave-screenshots/?complete");
   }).catch((e) => {
     mozlog.error("delete-account-error", {msg: "An error occurred trying to delete account", error: e});

server/src/servershot.js

@@ -620,42 +620,50 @@ Shot.deleteShot = function(backend, shotId, deviceId, accountId) {
   })
 };
 
-Shot.deleteEverythingForDevice = function(backend, deviceId) {
-  return db.select(
-    `SELECT images.id
-     FROM images JOIN data
-     ON images.shotid = data.id
-     WHERE data.deviceid = $1`,
-    [deviceId]
-  ).then((rows) => {
-      rows.forEach((row) => del(row.id))
+Shot.deleteEverythingForDevice = function(backend, deviceId, accountId) {
+  let deviceIds;
+
+  const getDeviceIds = () => {
+    if (accountId) {
+      return db.select(
+        `SELECT devices.id
+       FROM devices
+       WHERE devices.accountid = $1`,
+        [accountId]);
+    }
+    return Promise.resolve([{id: deviceId}]);
+  };
+
+  const imageIdsSelect = (deviceIdRows) => {
+    deviceIds = deviceIdRows.map(row => row.id);
+    if (!deviceIds.length) {
+      deviceIds = [deviceId];
     }
-  ).then(() => {
     return db.select(
-      `SELECT DISTINCT devices.id
-       FROM devices, devices AS devices2
-       WHERE devices.id = $1
-             OR (devices.accountid = devices2.accountid
-                 AND devices2.id = $1)
-      `,
-      [deviceId]);
-    }
-  ).then((rows) => {
-    let ids = [];
-    for (let i = 0; i < rows.length; i++) {
-      ids.push(rows[i].id);
-    }
-    if (!ids.length) {
-      ids = [deviceId];
-    }
+      `SELECT images.id
+       FROM images JOIN data
+       ON images.shotid = data.id
+       WHERE data.deviceid IN (${db.markersForArgs(1, deviceIds.length)})`,
+      deviceIds);
+  };
+
+  const deleteImageData = (imageIdRows) => {
+    imageIdRows.forEach(row => del(row.id));
+  };
+
+  const deleteShotRecords = () => {
     let deleteSql = `DELETE FROM data WHERE
-     deviceid IN (${db.markersForArgs(1, ids.length)})`;
+     deviceid IN (${db.markersForArgs(1, deviceIds.length)})`;
     return db.update(
       deleteSql,
-      ids
+      deviceIds
     );
+  }
 
-  });
+  return getDeviceIds()
+    .then(imageIdsSelect)
+    .then(deleteImageData)
+    .then(deleteShotRecords);
 };
 
 ClipRewrites = class ClipRewrites {