SQLite performance when executed first time - ionic4

Question

I am using SQLite with ionic
Ionic:
Ionic CLI : 6.6.0 (C:\Users\ADEEL\AppData\Roaming\npm\node_modules\#ionic\cli)
Ionic Framework : #ionic/angular 5.0.5
#angular-devkit/build-angular : 0.900.7
#angular-devkit/schematics : 9.0.7
#angular/cli : 9.0.7
#ionic/angular-toolkit : 2.2.0
Cordova:
Cordova CLI : 9.0.0 (cordova-lib#9.0.1)
Cordova Platforms : android 8.1.0, browser 6.0.0
Cordova Plugins : cordova-plugin-ionic-webview 4.1.3, (and 9 other plugins)
Utility:
cordova-res (update available: 0.13.0) : 0.6.0
native-run (update available: 1.0.0) : 0.2.8
System:
Android SDK Tools : 26.1.1 (C:\Users\ADEEL\AppData\Local\Android\Sdk)
NodeJS : v12.16.1 (C:\Program Files\nodejs\node.exe)
npm : 6.13.4
OS : Windows 10
I have a table with 16 records in log_book table and 1 record each in department and location. when i run the query first time it will take almost 15 to 20 seconds but after that it runs in milliseconds. Calling function as follow
getLogBooks(): Promise<LogBook[]>{
return this.storage.executeSql(`SELECT l.id, l.log_book_id, IFNULL(l.machine_no, "") machine_no , d.department_name, loc.location_name, l.section, l.area
FROM log_book l
INNER JOIN departments d ON l.department_id = d.id
INNER JOIN locations loc ON l.location_id = loc.id
WHERE l.deleted_at IS NULL`, [])
.then(res => {
const items: LogBook[] = [];
console.log('Log BOOK', res.rows.length)
if (res.rows.length > 0) {
for (let i = 0; i < res.rows.length; i++) {
items.push({
id: res.rows.item(i).id,
LogBookID: res.rows.item(i).log_book_id,
MachineNo: res.rows.item(i).machine_no,
Department: res.rows.item(i).department_name,
Location: res.rows.item(i).location_name,
Section: res.rows.item(i).section,
Area: res.rows.item(i).area
});
}
}
return items;
});
}
Table structure
CREATE TABLE IF NOT EXISTS `log_book` (
`id` integer primary key autoincrement,
`log_book_id` varchar(50) NOT NULL,
`machine_no` varchar(50) DEFAULT NULL,
`department_id` int(11) NOT NULL,
`location_id` int(11) NOT NULL,
`section` varchar(50) NOT NULL,
`area` varchar(50) NOT NULL,
`created_at` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP,
`updated_at` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP,
`created_by` int(11) DEFAULT NULL,
`updated_by` int(11) DEFAULT NULL,
`deleted_at` datetime DEFAULT NULL
);
CREATE TABLE IF NOT EXISTS `departments` (
`id` integer primary key autoincrement,
`department_name` varchar(50) NOT NULL,
`created_at` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP,
`updated_at` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP,
`created_by` int(11) DEFAULT NULL,
`updated_by` int(11) DEFAULT NULL,
`deleted_at` datetime DEFAULT NULL
);
CREATE TABLE IF NOT EXISTS `locations` (
`id` integer primary key autoincrement,
`location_name` varchar(50) NOT NULL,
`created_at` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP,
`updated_at` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP,
`created_by` int(11) DEFAULT NULL,
`updated_by` int(11) DEFAULT NULL,
`deleted_at` datetime DEFAULT NULL
);
What i am doing wrong.
Thanking you in anticipation