{"action":"created","comment":{"url":"https://api.github.com/repos/caskdata/cdap/pulls/comments/23659454","id":23659454,"diff_hunk":"@@ -81,30 +81,51 @@ Here are some rules to follow for Flows, Flowlets, Services, and Procedures:\n Keeping these guidelines in mind will help you write more efficient and faster-performing\n code.\n \n+Levels of Conflict Detection\n+----------------------------\n \n-The Need for Disabling Transactions\n------------------------------------\n Transactions providing ACID (atomicity, consistency, isolation, and durability) guarantees\n are useful in several applications where data accuracy is critical—examples include billing\n applications and computing click-through rates.\n \n-However, some applications—such as trending—might not need it. Applications that do not\n-strictly require accuracy can trade off accuracy against increased throughput by taking\n-advantage of not having to write/read all the data in a transaction.\n-\n-Disabling Transactions\n-----------------------\n-Transactions can be disabled for a Flow by annotating the Flow class with the\n-``@DisableTransaction`` annotation::\n-\n-  @DisableTransaction\n-  class MyExampleFlow implements Flow {\n-    ...\n-  }\n-\n-While this may speed up performance, if—for example—a Flowlet fails, the system would not\n-be able to roll back to its previous state. You will need to judge whether the increase in\n-performance offsets the increased risk of inaccurate data.\n+However, transaction are not for free: The transaction system must track all the writes\n+made by all transactions, and it must check transactions for conflicts before committing them.\n+Also, if conflicts are frequent, then they impact performance, because the failed transactions\n+have to be rolled back and reattempted.\n+\n+In some scenarios, you may want to fine-tune the way that a dataset participates in\n+transactions:\n+\n+- Some applications—such as trending—might not need transactions for all writes, because\n+  small inaccuracies have little effect on trends with great momentum. Applications that\n+  do not strictly require accuracy can trade it for increased throughput by disabling\n+  transactions for some datasets.\n+- Some applications perform concurrent updates to the same row of a table, but typically\n+  those updates do not strictly conflict with each other because they are on different\n+  columns of the row. In this case it can make sense to increase the precision of conflict\n+  detection by tracking changes at the column level instead of the row level.\n+\n+Both of these can be achieved by specifying a conflict detection level when the table is\n+created. Ffor example, in your application's ``configure()`` method::\n+\n+    Tables.createTable(getConfigurer(), \"myTable\", ConflictDetection.COLUMN);\n+\n+You have the following options:","path":"cdap-docs/developers-manual/source/building-blocks/transaction-system.rst","position":52,"original_position":52,"commit_id":"8f9e49e145c1ce0ea2b43940ef55c7999248bc1b","original_commit_id":"8f9e49e145c1ce0ea2b43940ef55c7999248bc1b","user":{"login":"anew","id":483004,"avatar_url":"https://avatars.githubusercontent.com/u/483004?v=3","gravatar_id":"","url":"https://api.github.com/users/anew","html_url":"https://github.com/anew","followers_url":"https://api.github.com/users/anew/followers","following_url":"https://api.github.com/users/anew/following{/other_user}","gists_url":"https://api.github.com/users/anew/gists{/gist_id}","starred_url":"https://api.github.com/users/anew/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/anew/subscriptions","organizations_url":"https://api.github.com/users/anew/orgs","repos_url":"https://api.github.com/users/anew/repos","events_url":"https://api.github.com/users/anew/events{/privacy}","received_events_url":"https://api.github.com/users/anew/received_events","type":"User","site_admin":false},"body":"ok","created_at":"2015-01-28T01:27:49Z","updated_at":"2015-01-28T01:27:49Z","html_url":"https://github.com/caskdata/cdap/pull/1141#discussion_r23659454","pull_request_url":"https://api.github.com/repos/caskdata/cdap/pulls/1141","_links":{"self":{"href":"https://api.github.com/repos/caskdata/cdap/pulls/comments/23659454"},"html":{"href":"https://github.com/caskdata/cdap/pull/1141#discussion_r23659454"},"pull_request":{"href":"https://api.github.com/repos/caskdata/cdap/pulls/1141"}}},"pull_request":{"url":"https://api.github.com/repos/caskdata/cdap/pulls/1141","id":28150293,"html_url":"https://github.com/caskdata/cdap/pull/1141","diff_url":"https://github.com/caskdata/cdap/pull/1141.diff","patch_url":"https://github.com/caskdata/cdap/pull/1141.patch","issue_url":"https://api.github.com/repos/caskdata/cdap/issues/1141","number":1141,"state":"open","locked":false,"title":"[CDAP-1279] remove @DisableTransaction and supporting code","user":{"login":"anew","id":483004,"avatar_url":"https://avatars.githubusercontent.com/u/483004?v=3","gravatar_id":"","url":"https://api.github.com/users/anew","html_url":"https://github.com/anew","followers_url":"https://api.github.com/users/anew/followers","following_url":"https://api.github.com/users/anew/following{/other_user}","gists_url":"https://api.github.com/users/anew/gists{/gist_id}","starred_url":"https://api.github.com/users/anew/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/anew/subscriptions","organizations_url":"https://api.github.com/users/anew/orgs","repos_url":"https://api.github.com/users/anew/repos","events_url":"https://api.github.com/users/anew/events{/privacy}","received_events_url":"https://api.github.com/users/anew/received_events","type":"User","site_admin":false},"body":"This removes the annotation itself, plus the support for it in program runners, data fabric facade, and guice modules. 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