Making GET_LOCK behavior more predictable cross version with query rewrite

MySQL has supported the GET_LOCK() function for a large part of its history. As the manual notes, GET_LOCK() can be used to implement application locks or to simulate record locks.

Changes in MySQL 5.7

In MySQL 5.7 we improved GET_LOCK() to be based on our internal meta-data locking system (MDL). This allowed us to lift the restriction that each subsequent call to GET_LOCK()would release all previous locks.

However, there is a chance that some applications depended on the previous behaviour of locks being released. For this subset of users, it is not always easy to inspect an application to see when this behaviour is required. This creates challenges in upgrading:

MySQL 5.6 Behavior

MySQL 5.7 Behavior

An additional incompatibility between the previous behaviour and new, is that lock names are now restricted to 64 characters in length.

Creating an upgrade path

The easiest way to be able to upgrade, is to make MySQL 5.7 behave more like MySQL 5.6 (at least initially). For new functionality, or over time as code has been inspected, the MySQL 5.7 behavior can be slowly introduced.

Using version-specific syntax it is possible to modify application code to use an implementation of GET_LOCK() that does exactly this:

(The /*!50700 means “only run this code in 5.7+”)

The second behavior change can be overcome by running the lock name through a hashing function. For example:

Previous Usage Backwards Compatible Usage
GET_LOCK(‘abc’, 10) GET_LOCK(sha1(‘abc’), 10)
RELEASE_LOCK(‘abc’) RELEASE_LOCK(sha1(‘abc’))
IS_FREE_LOCK(‘abc’) IS_FREE_LOCK(sha1(‘abc’))
IS_USED_LOCK(‘abc’) IS_USED_LOCK(sha1(‘abc’))

To combine both, the usage for GET_LOCK() would become:

Using Query Rewrite

MySQL 5.7 also supports a feature called Query rewrite (manual). With this feature it is possible to also make legacy application preserve the old get_lock behavior without needing to make any code changes. Here is a very simple example:

With this query rewrite rule installed I can repeat the original test-case as in MySQL 5.6. I have enabled warnings to be printed to assist in readability of when rewrites are happening:

Conclusion

I expect that this behavior change will affect only a small percentage of applications, as in most cases the previous behavior was not something that was useful to rely upon. None the less, it was a feature that had not changed in perhaps 10+ years, so it is good to be able to have a safe upgrade path.

[Source:- Mysqlserverteam]

MySQL creator says 14,000 against Oracle-Sun deal

Michael Widenius, the creator of the MySQL database and a vocal opponent of Oracle Corp’s USD 7 billion takeover of Sun Microsystems Inc, has handed 14,000 signatures opposing the deal to regulators in Europe, China and Russia. Widenius, one of the most respected developers of open-source software, left Sun last year to set up database firm Monty Program Ab, which competes directly with MySQL. The European Commission initially objected to Oracle’s acquisition of Sun, saying it was concerned Oracle’s takeover of the MySQL database could hurt competition in that market. But the Commission signaled in mid-December that it would likely clear the deal after some of Oracle’s largest customers said they believed the takeover would not hurt competition. Since then, Oracle has said it expects to win unconditional EU clearance to close the deal by the end of January. Widenius, who delivered the signatures on Monday, said he would continue to gather signatures until the commission makes a final ruling, which is due by Jan. 27. “Our signatories don’t have faith that Oracle could be a good steward of MySQL,” Widenius said in a statement. Still, Beau Buffier, a partner in the anti-trust practice of law firm Shearman & Sterling, said signature drives carry little weight with the commission. He said regulators generally want each person who weighs in on pending cases to provide specifics on how an acquisition might affect their particular business. “What you would need is detailed statements from significant developers,” he said. More than 5,000 signatures are from self-employed developers and more than 3,000 from employees of companies and other organizations using MySQL, according to Widenius. He did not disclose the names of the people who signed the petition. The signatures were gathered during the first week of the campaign and were delivered to the European Commission and other European institutions, including the European Parliament and the competition authorities of the 27 member states, as well as to the Chinese Ministry of Commerce and the Russian Federal Antimonopoly Service. Officials with Oracle, the world’s No. 3 software maker, and Sun, the No. 4 server maker, declined comment. The acquisition will transform Oracle from a maker of software into a technology powerhouse that sells computers and storage equipment preloaded with its programs. Oracle Chief Executive Larry Ellison is betting the combination will give his company an edge over rivals such as IBM Corp, Hewlett-Packard Co, Microsoft Corp and EMC Corp. Sun bought MySQL for USD 1 billion in 2008.

[Source:- Moneycontrol]

Apple recruits secure messaging app developer for summer internship

Developer behind encrypted app Signal working on Apple’s CoreOS Security team

[Source:- Macnn]

Digital transformation and smart city will drive APeJ IT services demand in 2016: IDC

IDC Asia/Pacific expects APeJ IT Services to be resilient – posting a 6.5% value growth year-on-year (YoY) (in US dollar) in 2016. The IT services market faced difficulties this year due to the depreciation of Asian currencies against the US dollar and the slowdown in China economy. Despite this, IDC believes APeJ IT services will remain positive next year with digital transformation and smart city initiatives driving demand for IT services.

Representational image: Reuters

Representational image: Reuters

“Demand is primarily being driven by digital transformation initiatives across verticals, particularly banking, retail and public sectors. Enterprises are increasingly leveraging 3rd platform technologies to build a cohesive digital agenda that focuses on achieving business outcomes. Smart City initiatives in countries such as China, India and Singapore have also fueled the demand for cloud, analytics, mobility and security solutions”, said Vidhika Sehgal , Senior Research Manager, Services, and IDC Asia/Pacific.

China, which has the largest IT services spend in APeJ, is expected to close the year with 9.4% YOY value growth in US dollar. Though historically known to have double digit growth, current estimates of 9.4% is still one of the highest growth markets in the region. In 2015, China saw the continued struggle of foreign players in the domestic market due to regulatory policies while local vendors witnessed a tapering in growth due to slower domestic demand.

“While exchange rate volatility can have a large impact on US dollar growth forecast in 2016, it is expected that growth in local currency will pick up in markets such as India and ASEAN, which should also contribute to an overall revival in APeJ IT services growth” adds Sehgal.

Within IT services segments, the market is being driven by growth in IT consulting, systems integration and hosting infrastructure service, mainly because of an increased migration to cloud. These three segments together contribute nearly 30% to APeJ IT services market. Consulting and integration services are in demand as companies look for third party services for identifying and implementing 3rd platform solutions to migrate legacy systems and also complement the existing IT architecture and contribute to business outcomes.

Growth in traditional outsourcing services continue to be adversely impacted by the shift to cloud, especially as deal size, duration and structure moves in favor of a more hybrid IT environment.

 
[Source:- Firstpost]

Apple releases public betas for iOS 9.3 and OS X 10.11.4

Every Apple operating system has a new developer beta available now, and iOS and OS X have new public betas out too.

apple beta software ios osx
It’s a field day for beta testers, as Apple has released new developer betas for all of its operating systems—iOS 9.3, OS X 10.11.4, watchOS2.2, and tvOS 9.2. Participants in the public betas can get their hands on the betas for iOS and OS X.

If you’re enrolled in the developer program, hit up the Developer Center. If you’re not a registered developer, but still want to test drive these new beta features, you can sign up for the Public Beta program. The public betas for iOS and OS X usually trail the developer beta releases by a few days. UPDATE February 23, 11:40 a.m. Pacific: iOS 9.3 and OS X 10.11.4 are now in public beta.

According to 9to5Mac, the official versions of iOS 9.3 and OS X 10.11.14 are expected to launch around Apple’s March 15th event. Here’s a breakdown of all the new feature we got.

iOS 9.3 beta 4

The all-new, system-wide Night Shift mode will automatically adjust the display colors on your iPhone, iPad, or iPod touch. Once the mode is enabled, the colors will shift “to the warmer end of the spectrum” starting at sunset and revert back to normal in the morning. The main reason is get rid of the stark bright blue light that makes it difficult to go sleep at night.

Other features in iOS 9.3 include setting a password or Touch ID to open the Notes app, and you can also set individual notes to be password-protected. ForiPhone 6s and 6s Plus users, iOS 9.3 adds 3D Touch support for a few moreApple apps, including Settings. Deep press on the Settings app icon to launch a Quick Action shortcut to tinker with Battery, Bluetooth, and Wi-Fi. And finally, iOS 9.3 supports Wi-Fi Calling for Verizon customers, following AT&T and T-Mobile.

In addition, iOS 9.3 also brings landscape support in the News app, HealthKit-enabled app suggestions in the Health app, PDF-syncing via iCloud for iBooks, better Apple Music and Maps integrations in CarPlay, as well as a few new education features for managing shared iPads in a classroom setting.

OS X 10.11.14 beta 4

This beta version of OS X El Capitan comes with support of Live Photos, the moving images that can be taken with the new iPhone 6s and 6s Plus. Prior to OS X 10.11.14, you could only view Live Photos on the Mac via the Photos app, and sharing was limited to iCloud Photo Sharing. In this developer beta, you can now view and send Live Photos via the Messages app on your Mac.

Just like in iOS 9.3, OS X 10.11.4 also brings support for making the Notes app password-protected. And you will also be able to import data from other note-taking apps, including Evernote. The official OS X 10.11.14 update will also be accompanied by a new version of iTunes.

watchOS 2.2 developer beta 4

This software update for Apple Watch gives the Maps app new features. With watchOS 2.2, you can launch the Maps app and have it instantly navigate to your given destination. You can also tap to find businesses with a “Nearby” feature powered by Yelp.

Once your iPhone gets updated to iOS 9.3, you will be able to pair multiple AppleWatches. This watchOS update will be able to recognize which Watch is active at any given time and switch between the different devices.

tvOS 9.2 developer beta 4

The software update for the fourth-generation Apple TV incorporates elements of iOS. With tvOS 9.2, you will be able to organize your apps into folders and switch between apps via a redesigned app switcher.

You will also be able to talk to the Siri Remote to dictate into text fields to search for content or even spell out your usernames and passwords. Other features coming to along tvOS 9.2 include support for iCloud Photo Library, Bluetoothkeyboards, and conference room mode.

[Source:- Macworld]

Apple enumerates cooperation with FBI in San Bernadino iPhone 5c case

In a court filing made yesterday, Apple’s head of the global privacy and law enforcement compliance team, spelled out Apple’s responses to the myriad subpoenas that the company received to collect data on the San Bernadino shooters. Manager Lisa Olle declared that in many cases, including just days after the incident, that Apple not only collected multiple data requests from the FBI, but in many cases, acted upon the request and provided compelled data on the same day that the court order arrived in Cupertino.

Olle laid out in the timetable that after an initial phone call early December 5, Apple was served four times for data. The initial request was made on December 5 for three names and nine accounts. December 6 saw requests for three accounts, with same day service. On December 16, the FBI sought information on one name and seven accounts, and Apple delivered that day as well.

The search warrant for the suspect’s iCloud device was served on Friday, January 22, a month and a half after the shooting. All of the information in Apple’s posession was handed over on Tuesday, January 26. The Ex Parte application for Apple to develop the break-in tool for the county-owned iPhone 5c at the center of the case was served on February 16.

Olle, as manager of the law enforcement coordination team, also spelled out what she believes is required of Apple to conform to the application. Above and beyond the engineering effort needed to code the break-in tool, the department head is calling for one or two facilities similar to a US government “Sensitive Compartmented Information Facility,” which would need to be “tightly controlled and monitored around the clock.” Also noted is the difficulty of communicating data, device accountability, and the need for “technical escalations” when dealing with law enforcement officials.

Laying down the groundwork for an “undue burden” defense, Olle also notes that she is expecting more law enforcement agencies to also request the use of the tool the FBI is demanding and Apple “would need to hire people whose sole function would be to assist with processing and effectuating such orders.” These new hires “would have no other necessary business or operations function at Apple” and would include paralegals, engineers, and forensic specialists dedicated to trial work.

 
[Source:- Macnn]

Clicking, scanning, tapping and swiping to new age supply chain management

Conceived decades ago as the way forward for manufacturers who sought to harness technology to better plan business operations, ERP has been used to patch up disparate systems and processes to provide an integrated information flow to an organization. With technological advances and the explosive growth of companies like Amazon – online to offline, e-commerce, real time delivery, and drones – the logistics and supply chain industry of the new era needs entirely new levels of speed, accuracy, efficiency and cohesion from its ERP systems and other solutions that they use for driving business.

The traditional model of patchwork for disparate systems, along with the legacy roots in manufacturing, leaves these logistics and supply chain companies with a software that does not cover their operations comprehensively, creating gaps in vital functions. While a traditional ERP has tried to meet warehousing needs, integrating stacking and racking; companies are now demanding much higher levels of precision, real-time tracking and response systems, to manage the highly dynamic requirements of the modern supply chain business.

Thinkstock

Thinkstock

The nature of modern business, thus, makes it imperative for ERP vendors, and businesses as well, to think of ERP in a totally new context. There needs to be a fundamental shift in the way in which ERP usage is viewed, from a system of records to a system of insights and action. This system must gel with the usage patterns of new generation application users, who are tuned highly into social media. This system must, at the same time, provide high-level automation of routine functions, enabling all levels of user hierarchy manage by exception and ensuring quality time for users, to focus on strategy and innovations.

Logistics and technological advances such as Near-Field Communication (NFC), GPS, QR Codes, RFID tags and sensors have to be utilised and integrated with the ERP applications, in order to automate inventory transactions and maximise warehouse space and inventory. Store transactions getting completed in a jiffy, through a couple of scans of QR Codes have been in the mainstream for some time now. GPS enabled tracking of consignments and the ability to visualize real-time status through Google Maps, has brought tremendous benefits to many businesses, already. By using trend analysis through integrated data analytics, one can efficiently arrange warehouse space, ensuring high-traffic items are placed near loading doors, for quick movement. Additionally, in order to forecast demand and plan inventory effectively, one can leverage multi-agent based technology for real-time scheduling, Route Planning and Load Optimization and Inventory Forecasting. This will in turn increase the processing capacity, drastically, ensuring faster and smarter decisions. Also, Big data analytics using the terra bytes of data made available through Internet of Things is the other huge area both supply chain companies and the ERP vendors must focus together on.

Mobility solutions are now key for any organization. Smartphones are no longer news, they are a necessity. The smartphone penetration is increasing by leaps and bounds, globally. In a business context, there is always a need to be connected to the latest information, in order to make the best decisions. Being able to manage operations via smart devices gives flexibility and places critical information within reach, allowing thorough evaluations during any situation. Overseeing and managing the supply chain by walking around is no longer impossible, it is now mandatory for business success. Any ERP that lets a user carry out his or her day-to-day work through a mobile device – take customer orders, track statuses of an invoice, authorize a document, apply for leave – is bound to have a legion of fans in an organization.

Companies need to gain a competitive edge in today’s market. Ensuring that processes run at optimum levels is not enough. An organization must be able to make accurate, instantaneous changes and decisions. Real-time tracking of warehouse utilisation, supply chain movements and inventory status is now necessary for warehouse workers and top management to make decisions.

All this being said, user-friendliness is still key to determining whether an ERP is properly utilised. If the ordinary logistics worker is unwilling or unable to use the ERP, the system will lack necessary critical information. It is just as important to have an intuitive interface that can be used by everyone from upper management to workers, on the warehouse floor. Building on the new need for analytics, ERP software should also be context-aware. As businesses grow and shrink with the market, their internal functions have to adjust, accordingly. Having this foresight can make the difference between a successful or failed implementation.

As technology advances, and newer business models appear on the horizon, ERP solutions need to not only catch up and stay in tune with the technology trends, but also be agile enough to mould themselves into the ever evolving business models, to fit the needs of the various industries they serve. No longer can traditional ERP platforms shoehorn other business segments into legacy systems. ERP must be redesigned so that it can break away from its legacy manufacturing roots and create a platform to deliver and serve the needs of many.

 

[Source:- Firstpost]

Best USB-C battery pack: We review portable batteries for the latest MacBook and iOS devices

usbc batteries group shot bg focus

USB Type-C (or USB-C) had its coming-out party quite late—at this year’s CES in early January, even though the connection type made its broad debut with Apple’s 12-inch MacBook in April 2015. Since then, more devices have adopted the format, such as the Chrome Pixel C and Nexus 6P. (The new Apple TV has a USB-C port but only as a connection option for debugging and making screen captures with a Mac.) An ocean of USB-C devices is coming that will include more Macs as part of the Thunderbolt 3 update—which relies on that connector style—and possibly some iOS hardware.

I’ve been waiting to test USB portable batteries equipped with USB-C since theMacBook shipped. But as long as Apple relied on the MagSafe connector, you couldn’t get a licensed and certified adapter that would work with a Mac laptop. USB-C changes that altogether. It has bi-drectional power support, allowing energy to flow from a laptop or other controller’s USB-C to charge or power external devices and via USB-C to charge a MacBook or similar device’s internalbattery.

Power packs

In general, USB battery packs used to have limited capacity, offer slow charging of devices and recharge slowly, and cost and weigh a lot relative to the benefit they offer. But they’ve matured very rapidly over the last few years. With the very large-scale manufacture of standard-sized rechargeable lithium-ion battery cells, electronics makers have created affordable, high-capacity USB packs that range from recharging your iPhone 6s by about 50 percent up to the equivalent of a week’s worth of multiple full recharges of a set of iPads and iPhones.

Laptops have typically been in a different category, because they not only have large batteries, but when in use, they draw power faster than previous USB packs typically provide it because of limitation in the previous generation of USB connector and cable standards. In such a case, a Mac laptop pulls juice from the USB-connected battery, but also gradually runs down its internal one.

The iPad Pro suffers from this problem. It ships with a 12-watt power adapter that can’t always keep up with power consumed while you’re using the iPad Pro. While its battery could safely be charged at a much higher wattage (at least twice as “fast” in terms of power flow), the Lightning standard appears to limit its maximum rate.

USB-C breaks through that limit by allowing higher-amperage charging even though USB has a set limit on voltage. (Wattage is the product of amps times volts, representing the total energy transferred.) This higher amperage can allow a USB battery pack to recharge a 12-inch MacBook relatively speedy when put to sleep, although the units I tested still can’t keep up with its power consumption.

OS X requires changes to better recognize the kind of external device providing charge, rather than treating them as a “power adapter” as the MacBook did for all the batteries tested.

USB-C’s higher rate of power flow lets some of the batteries I tested recharge rapidly, although you need to find a high-wattage USB adapter to make that work as well—none ship with such an adapter. (One pack can use Qualcomm’s Quick Charge 2.0 technology, which boosts voltage for faster charger when used with a USB power adapter with the same tech.)

Being able to bring a relatively lightweight battery (half a pound to a pound) that carries a partial or full additional MacBook charge or could partly recharge aMacBook and handle an iPhone and iPad (some charging three devices simultaneously) can make extended travel away from electricity very practical. This can especially include long-haul flights where onboard power isn’t available or that power isn’t enough to charge devices fully. You would no longer have to camp at an outlet or leave hardware in a vulnerable place to charge via AC.

GLENN FLEISHMAN
From top to bottom: Talentcell 10400mAh 38Wh Portable Charger, Monoprice Select Series Portable Cell Phone Charger, Anker PowerCore+ 20100, and RAVPower 20100mAh ExternalBattery Pack.

In this roundup, I look at four USB packs that feature a USB-C port for charging; some can also recharge through the port. These models appeared on the market starting in fourth quarter 2015, and three are from companies with good track records on electronics, cables, or batteries. (The fourth is less known, but itsbattery tested very well.) I tasked them to discharge and recharge on their own, and replenish a USB-C MacBook.

Juice it up

Unlike the fancy design-to-purpose batteries you’ll find inside Apple products, every USB battery pack I’m aware of uses cells purchased from a battery-making firm. Apple and other companies mold or terrace lithium-ion (Li-ion) polymer batteries to fit every nook and cranny. Mass-produced cells, however, are typically round, like normal alkaline and rechargeable consumer batteries, although they are often much larger.

While some small packs use flat arrangement to stay compact—such as Amazon’s super-cheap $6 Micro-USB Portable Power Bank—larger USB packs like the ones I tested rely on standard cylindrical cells and package them with the circuitry, heat dissipation, and connectors needed to move power in and out.

If you’re not familiar with power basics, here are just a few. The simplest way to discuss electrical power is in units of volts (V), amperes or amps (A), and watts (W). These can be compared to water pipes and water flow. Voltage is pressure, or the amount of water in a given space; amperage is pipe diameter, which has an impact on pressure. Low-amperage (a small diameter pipe) requires high voltage (lots of pressure) to move the same amount of power as a high-amperage (big diameter pipe) with low pressure (low voltage). Wattage is the product of amps and volts, describing the power (the “work”) passing through the system.

Now, with batteries and battery packs, we want to describe how much capacitythey have—how much power they can store and then provide to other hardware. That’s measured in milliampere-hours, abbreviated mAh, which you’ve probably seen repeatedly and wondered precisely what it meant. That number can be confusing because it also requires a voltage, something you rarely see listed. The batteries used in power packs typically discharge at about 3.6V or 3.7V and charge at 4.2V. (Lithium-ion cells, used for all the packs I tested, charge best at about that rate.)

So when you see that a battery pack has 10,000 mAh, that’s 10,000 mAh available at 3.6V. USB, however, is 5V, while smartphone batteries used in iOS devices discharge at about 3.8V (and charge around 4.3V or 4.4V). This requires converting voltage to figure out the idealized capacity. Because these voltages are so similar, you can mostly ignore that; it mostly matters with higher-voltage device batteries. (A similar measure, watt-hours (Wh), avoids this conversion, but because it’s not consistently used, it’s harder to find it for comparison.)

As an example, the iPhone 6s battery has 1,715 mAh of capacity. That should mean that a 10,000 mAh USB battery can recharge it about 5.5 times. (For comparison, the iPad Air has a 7,340 mAh and the iPad Pro a 10,307 mAh one.) The single-port MacBook is a trickier case, because its internal battery is 5,263 mAh but at 7.55V. If you do the math, 3.6 divided by 7.55 gets you the factor to multiply against the battery pack’s pack—roughly 50 percent or about 5,000 mAh. So you should be able to charge a MacBook from 0 to 100 percent almost twice with such a pack, right?

But that omits three other factors! Bear with me, as these are easier to explain:

  • Because power has to be converted among voltages to work over USB, both in the source battery and in the destination device, there’s always some loss. This is why you feel heat when batteries charge or discharge, as heat is wasted energy. (Some of the devices I tested seem to get noticeably hotter than others.)
  • Lithium-ion batteries can’t be taken down entirely to zero percent. As a spokesperson at Anker, the maker of many batteries and one best one we tested, conveyed from its engineers, “If the battery power is discharged to zero it will adversely affect the durability of the battery cell.” So even when seemingly exhausting a USB battery pack, its circuitry prevents it from tapping out.
  • Li-ion batteries also degrade over time and have a risk of expansion or even fires if they’re overcharged or charged too close to full too fast. (For reference, see all the Hoverboard fire videos from this last fall.) USB packs can charge rapidly at first, but as batteries approach full, they slow down, and stop short of 100 percent—sometimes far short in my testing.

To sum up? Batteries can’t give up their last ergs of juice, can’t be charged to 100 percent (and you never know quite how close), and lose power in converting over USB and back. This adds up.

In my testing, the best of the two highest-capacity batteries (both over 20,000 mAh) delivered 55 percent of its rated capacity to a MacBook. That was still enough to completely recharge a MacBook battery with some left over, which is magnificent both for performance and by price and weight. But it’s not as much as you’d reckon by using rated numbers alone. I’ll get into this more with individual reviews.

Another factor with power is “speed”—in this case, that’s directly related to amperage. Because USB’s voltage is fixed at around 5V, you have to up the amps to move more power, which equates to moving power “faster.” Devices with larger batteries, like tablets or these large USB battery packs, need high-amperage chargers to refill them in any reasonable amount of time. You also need high amperage to charge a device faster than it’s depleting power if it’s in use while charging.

Originally, most USB packs maxed out with ports that could each pass power at about 1A, fast enough to charge a smartphone at full speed. But an iPad Air 2and iPad Pro can charge at 2.4A (and the Pro even faster with a higher-amperage adapter), and iPhones for years charge fine at 1A, but can bump up to as fast as 2.1A with an iPad charger.

Modern packs typically have ports that can be rated at 2.0A, 2.1A, or 2.4A; all the packs tested have at least one Type-A 2.4A port, and one USB-C 3A port. Modern packs also use USB and other signaling to provide as much power as a device can accept but no more, while mobiles and computers won’t accept more power than they can safely use. (USB packs’ ports default to 1A or lower if they can’t sort this out with an attached device.)

Faster only works to a point: For keeping their lives long, batteries should only be charged between about a 0.50 and 1.00 ratio of amperage to capacity, which is called its C rating. An iPhone with a 1,715 mAh battery charging at 1A has a 0.58C rating, considered “gentle” and which maximizes cycles. Charge it at 2.1A, and you’re well above 1C, but Apple appears to have factored in, as it allows charging at that high a rate. The USB power packs I tested charge at about 0.15C to 0.30C; future packs might work with higher-wattage cables and adapters for faster recharge rates.

Only the Talentcell provided guidance as to the number of cycles it expects for the pack to perform as expected: 500. As with all lithium-ion charging cycles, that typically refers to complete cycles, so depleting to 50 percent and charging to full counts as a half cycle.

Finally (whew!) each battery pack has a maximum combined output across all ports. The internal electrical circuitry divvies up charge by port, but also can’t exceed that total when charging through multiple ports at once, like multiple iPads and iPhones. For example, the Anker PowerCore+ 20100 can output 2.4A on its two Type-A ports and 3A on its USB-C ports. With all three ports in use, however, it maxes out at 6A, with no more than 2.4A to any port.

 

[Source:- Macworld]

Apple board re-elected, proposals rejected at shareholder meeting

Cook tells investors that fight with FBI over privacy ‘doesn’t scare us’

What to do with optimizer hints after an upgrade?

At a recent optimizer webinar, I talked about MySQL introducing a new style for hints, and that MySQL 5.7 also added support for more hints, see Sergey Glukhov’s blog. A question I got at the end of the webinar was what to do with the hints in the application code after an upgrade?

The MySQL optimizer makes decisions on which query plan to choose based on the built-in cost model and statistics from storage engines, in addition to dictionary information. For each release, the optimizer gets smarter and smarter, the cost model becomes more advanced, statistics gets more fine grained, and with the planned histogram support, the optimizer will also get more information on data distribution.

While optimizer improves for each release, query plans a user has specified using hints in the application code remain unchanged. These hints may not be needed after an upgrade, and in the worst case, they can become counterproductive. We advise users to retest hints during upgrade and drop those that are no longer needed. This works fine if you have full control over the application code, but it doesn’t work if you don’t.

In 5.7, MySQL introduced a query rewrite plugin which can be very useful in such a scenario. Instead of adding hints directly into the application code, it allows users to rewrite a query by adding hints through the query rewrite plugin. Martin’s blog shows how to rewrite a query using this new plugin. During an upgrade, users can simply get a list of all rewrite rules from the rewrite_rules table, and then they can easily enable and disable each rewrite rule to verify if the hint is still useful. If not, the rewrite rule can be removed without changing any application code.

 

[Source:- Mysqlserverteam]