당신이 어떤 일을 해낼 수 있는지 누군가가 물어보면 대답해라.

"물론이죠!" 그 다음 어떻게 그 일을 해낼 수 있을지 부지런히 고민하라.

- 시어도어 루스벨트

Is Safari on iOS 6 caching $.ajax results?

$.ajaxPrefilter(function (options, originalOptions, jqXHR) {
    // you can use originalOptions.type || options.type to restrict specific type of requests
    options.data = jQuery.param($.extend(originalOptions.data||{}, { 
      timeStamp: new Date().getTime()
    }));
});

iOS6 Safari orientation change bug?

Safari Overflow Hidden Problem

There may be times when you need to hide the overflow (scrollbars) being visible on a page. You can specify to have all scrollbars hidden or the x and y scroll bars separately. When trying to hide the overflow of a project I was working on I realized that the ‘overflow:hidden’ was not working on the Safari browser. This was very frustrating because it worked on all other browsers except Safari. Well, there is a very simple solution to solve this problem… All you have to do is set that element to have a relative position. For instance, if you were to specify for the body to hide the horizontal scrollbars you would want to have the following css in your stylesheet:

 
body {
	position:relative;
	overflow-x:hidden;
}

iOS 6 Beta 1: HTML5 new APIs, Remote Debugging and native apps integration

Public new features for Safari on iOS 6

File uploads

Finally! We can now select an image from the Photo Library or opening the Camera from a web form. The question is about HTML Media Capture being implemented or not (see later for the answer).

Web Audio API

With the Web Audio API we can enhance HTML5 games and multimedia apps with mixing, filtering and processing operations through JavaScript.

CSS Filters

CSS 3 Filters a set of image operations (filters) that we can apply using CSS functions, such as grayscale, blur, drop-shadow, brightness and other effects. These functions will be applied before the content is rendered on screen. We can use multiple filters using spaces (similar to transforms).

Smart App Banners

It’s a way to connect websites to native applications. When you browse a web that has a related native application, Safari can show a banner inviting the user to install or open the native app. The website can also send parameters to the native app. It’s not clear how this is going to be implemented. My guess is through meta tags. The same behavior is available on Internet Explorer 10 for Windows 8.

Full Screen support on landscape

When you orient your device in landscape mode you can then move to a full-screen mode, including hiding the status bar and the Safari toolbar at the bottom. Transparent buttons are replacing the toolbar. A similar behavior is available on Nokia Browser for Symbian.  It’s not clear at this point if we can use the FullScreen API to request the feature (see later for the answer)

Remote Web Inspector

This is a big feature. Announced as a very small feature in the new APIs for developers. In the keynote there was no other information. As you may know, I’ve developed iWebInspector for iOS 5 because of the lack (or the hiding) of a web inspector tool for debugging web apps. It’s not public if this new Remote Web Inspector through LAN (like BlackBerry Remote Web Inspector) or through USB (like Google Chrome for Android)… the answer, later in this post.

Crossfade CSS Function

This feature was published in the keynote with “font-face: 3px” but I’ve seen it. It’s an image function that will create a crossfade between two images (Spec draft), for example:

Will it work with transitions?

Other announced features and questions

iCloud Tabs

You can synchronize your tabs between all your devices, including Macs, iPhones and iPads. So the same URL will be distributed through all devices. Be careful on your mobile web architecture!

Offline Reading List

when the user adds a page to the reading list it will be also downloaded and precache. Is there any API to know if our page is being executed from the cache?

Maps

Google Maps native app was replaced by a new Maps app (directly from Apple). The question is, is this app still capturing http://maps.google.com URLs? (I hope not) and how to open the native app or driving instructions from a web.

Twitter and Facebook

Both social networks are not integrated in the operating system. It will be good if at some point web apps can also use these credentials.

Questions from the past

WebGL? IndexedDB? getUserMedia (camera access)? Nitro engine on Web Views?

/*+ ALL_ROWS */

  ALL_ROWS는 Full Table Scan을 선호하며 CBO(Cost Based Optimization)는 default로 ALL_ROWS를 선택 합니다.

 
SQL> SELECT /*+ ALL_ROWS */  ename, hiredate 
     FROM emp  
     WHERE ename like '%%%';
       
Execution Plan
----------------------------------------------------------
   0      SELECT STATEMENT Optimizer=HINT: ALL_ROWS (Cost=1 Card=5 Bytes=80)
   1    0   TABLE ACCESS (FULL) OF 'EMP' (Cost=1 Card=5 Bytes=80)
    

/*+ CHOOSE */

  Hint Level의 CHOOSE는 RBO(Rule Based Optimization)인지 CBO(Cost Based Optimization) 인지를 선택 합니다. 만약 주어진 table의 통계 정보가 없다면 Rule Based 접근 방식을 사용 합니다.

/*+ FIRST_ROWS */

  Full Table Scan보다는 index scan을 선호하며 Interactive Application인 경우 best response time을 제공 합니다. 또한 sort merge join보다는 nested loop join을 선호 합니다.

 
SQL> SELECT /*+ FIRST_ROWS */  ename 
     FROM emp 
     WHERE empno=7876;
 
Execution Plan
----------------------------------------------------------
   0      SELECT STATEMENT Optimizer=HINT: FIRST_ROWS (Cost=1 Card=1 Bytes=20)
   1    0   TABLE ACCESS (BY INDEX ROWID) OF 'EMP' (Cost=1 Card=1 Bytes=20)
   2    1     INDEX (RANGE SCAN) OF 'PK_EMP' (UNIQUE) (Cost=1 Card=1)
    

/*+ RULE */

  Rule Based 접근 방식을 사용하도록 지정 합니다.

/*+ CLUSTER(table_name) */

  Cluster Scan을 선택하도록 지정한다. 따라서 clustered object들에만 적용 됩니다.

/*+ FULL(table_name) */

  Table을 Full Scan하길 원할 때 사용 합니다.

/*+ HASH(table) */

  Hash scan을 선택하도록 지정한다. 이 hint는 HASHKEYS parameter를 가지고 만들어진 cluster내에 저장된 table에만 적용이 됩니다.

/*+ INDEX(table_name index_name) */

  지정된 index를 강제적으로 쓰게끔 지정 합니다.

/*+ INDEX_ASC(table_name index_name) */

  지정된 index를 오름차순으로 쓰게끔 지정 합니다. Default로 Index Scan은 오름차순 입니다

/*+ INDEX_DESC(table_name index_name) */

  지정된 index를 내림차순으로 쓰게끔 지정 합니다.

  아래 예제는 제일 큰 것 하나만 조회되므로, max 함수의 기능을 대신할 수 있습니다.

 
SQL> SELECT /*+ index_desc(emp pk_emp) */  empno
     FROM   emp
     WHERE  rownum = 1 ;
    

/*+ INDEX_FFS(table index) */

  Full table scan보다 빠른 Full index scan을 유도 합니다.

/*+ ORDERED */

  From절에 기술된 테이블 순서대로 join이 일어나도록 유도 합니다.

/*+ USE_HASH (table_name) */

  각 테이블간 HASH JOIN이 일어나도록 유도 합니다.

*+ USE_MERGE (table_name) */

  지정된 테이블들의 조인이 SORT-MERGE형식으로 일어나도록 유도 합니다.

/*+ NOPARALLEL(table_name) */

  NOPARALLEL hint를 사용하면, parallel query option을 사용하지 않도록 할 수 있다.

/*+ PARALLEL(table_name, degree) */

  PARALLEL hint를 사용하면 query에 포함된 table의 degree를 설정할 수 있습니다.

  예를 들어, 다음과 같이 hint를 적어 degree 4로 parallel query option을 실행하도록 할 수 있습니다. 이 때 parallel이란 글자와 괄호( '(' )사이에 blank를 넣지 않도록 주의해야 합니다.

 
SQL> SELECT /*+ PARALLEL(emp, 4) */   * 
     FROM emp;
    

DEGREE의 의미 및 결정

  Parallel Query에서 degree란 하나의 operation 수행에 대한 server process의 개수 입니다. 이러한 degree 결정에 영향을 주는 요인들에는 다음과 같은 것들이 있습니다.

• (1) system의 CPU 갯수
• (2) system의 maximum process 갯수
• (3) table이 striping되어 있는 경우, 그 table이 걸쳐있는 disk의 갯수
• (4) data의 위치 (즉, memory에 cache되어 있는지, disk에 있는지)
• (5) query의 형태 (예를 들어 sorts 혹은 full table scan)

  한 사용자만이 parallel query를 사용하는 경우, sorting이 많이 필요한 작업과 같은 CPU-bound 작업의 경우는 CPU 갯수의 1 ~ 2배의 degree가 적당하며, sorting보다는 table scan과 같은 I/O bound 작업의 경우는 disk drive 갯수의 1 ~ 2배가 적당합니다.

  동시에 수행되는 parallel query가 많은 경우에는 위의 각 사용자의 degree를 줄이거나 동시에 사용하는 사용자 수를 줄여야 합니다.