Comments on: Guide on GUIDs http://bhavin.directi.com/guide-on-guids/ Tue, 7 Sep 2010 09:45:29 +0000 http://wordpress.org/?v=2.9.1 hourly 1 By: fivefigers shoe http://bhavin.directi.com/guide-on-guids/comment-page-1/#comment-16369 fivefigers shoe Thu, 15 Jul 2010 08:21:46 +0000 http://bhavin.directi.com/?p=261#comment-16369 Although vibram flow walking over gravel in my Vibrams was a little vibram sprint uncomfortable, the rest of the hike was extremely fun and vibram fivefingers kso enjoyable. I am wanting to work out in my vibram 5fingers every day!Most of the vibram shoes sale, the fact that it is indeed more harm than good. The problem is that these shoes in order to “protect” in such a way that they should not be his leg. After the over-built five finger shoes muscles, tendons and ligaments of the lower limb atrophy conclusions. This is because your five fingers shoe do the work, your legs and feet should do.http://www.fivefingeronline.com/ Although vibram flow walking over gravel in my Vibrams was a little vibram sprint uncomfortable, the rest of the hike was extremely fun and vibram fivefingers kso enjoyable. I am wanting to work out in my vibram 5fingers every day!Most of the vibram shoes sale, the fact that it is indeed more harm than good. The problem is that these shoes in order to “protect” in such a way that they should not be his leg. After the over-built five finger shoes muscles, tendons and ligaments of the lower limb atrophy conclusions. This is because your five fingers shoe do the work, your legs and feet should do.http://www.fivefingeronline.com/

]]> By: Bhavin Turakhia http://bhavin.directi.com/guide-on-guids/comment-page-1/#comment-15570 Bhavin Turakhia Thu, 31 Dec 2009 11:02:44 +0000 http://bhavin.directi.com/?p=261#comment-15570 *ramki: except that if you are using them to substitute your regular rdbms auto increment on the server then using MAC / URIs etc will infact increase the collision chance as opposed to reducing it *ramki: except that if you are using them to substitute your regular rdbms auto increment on the server then using MAC / URIs etc will infact increase the collision chance as opposed to reducing it

]]> By: Ramki Gaddipati http://bhavin.directi.com/guide-on-guids/comment-page-1/#comment-15569 Ramki Gaddipati Thu, 31 Dec 2009 10:46:04 +0000 http://bhavin.directi.com/?p=261#comment-15569 An extract from MySQL reference manual, as an example •UUID() Returns a Universal Unique Identifier (UUID) generated according to “DCE 1.1: Remote Procedure Call” (Appendix A) CAE (Common Applications Environment) Specifications published by The Open Group in October 1997 (Document Number C706, http://www.opengroup.org/public/pubs/catalog/c706.htm). A UUID is designed as a number that is globally unique in space and time. Two calls to UUID() are expected to generate two different values, even if these calls are performed on two separate computers that are not connected to each other. A UUID is a 128-bit number represented by a utf8 string of five hexadecimal numbers in aaaaaaaa-bbbb-cccc-dddd-eeeeeeeeeeee format: ■The first three numbers are generated from a timestamp. ■The fourth number preserves temporal uniqueness in case the timestamp value loses monotonicity (for example, due to daylight saving time). ■The fifth number is an IEEE 802 node number that provides spatial uniqueness. A random number is substituted if the latter is not available (for example, because the host computer has no Ethernet card, or we do not know how to find the hardware address of an interface on your operating system). In this case, spatial uniqueness cannot be guaranteed. Nevertheless, a collision should have very low probability. Currently, the MAC address of an interface is taken into account only on FreeBSD and Linux. On other operating systems, MySQL uses a randomly generated 48-bit number. http://dev.mysql.com/doc/refman/5.0/en/miscellaneous-functions.html#function_uuid An extract from MySQL reference manual, as an example

•UUID()

Returns a Universal Unique Identifier (UUID) generated according to “DCE 1.1: Remote Procedure Call” (Appendix A) CAE (Common Applications Environment) Specifications published by The Open Group in October 1997 (Document Number C706, http://www.opengroup.org/public/pubs/catalog/c706.htm).
A UUID is designed as a number that is globally unique in space and time. Two calls to UUID() are expected to generate two different values, even if these calls are performed on two separate computers that are not connected to each other.
A UUID is a 128-bit number represented by a utf8 string of five hexadecimal numbers in aaaaaaaa-bbbb-cccc-dddd-eeeeeeeeeeee format:
■The first three numbers are generated from a timestamp.
■The fourth number preserves temporal uniqueness in case the timestamp value loses monotonicity (for example, due to daylight saving time).
■The fifth number is an IEEE 802 node number that provides spatial uniqueness. A random number is substituted if the latter is not available (for example, because the host computer has no Ethernet card, or we do not know how to find the hardware address of an interface on your operating system). In this case, spatial uniqueness cannot be guaranteed. Nevertheless, a collision should have very low probability.
Currently, the MAC address of an interface is taken into account only on FreeBSD and Linux. On other operating systems, MySQL uses a randomly generated 48-bit number.

http://dev.mysql.com/doc/refman/5.0/en/miscellaneous-functions.html#function_uuid

]]> By: Ramki Gaddipati http://bhavin.directi.com/guide-on-guids/comment-page-1/#comment-15568 Ramki Gaddipati Thu, 31 Dec 2009 10:43:55 +0000 http://bhavin.directi.com/?p=261#comment-15568 The generation of UUIDs is not truly random. Most implementations are based on certain values in the problem/solution domain which are assumed/expected to be unique, to avoid even those small chances of collisions, like MAC, URIs, UserIds so on. http://en.wikipedia.org/wiki/UUID The generation of UUIDs is not truly random. Most implementations are based on certain values in the problem/solution domain which are assumed/expected to be unique, to avoid even those small chances of collisions, like MAC, URIs, UserIds so on.

http://en.wikipedia.org/wiki/UUID

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