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courses:mapreduce-tutorial:perl-api [2012/01/23 21:20]
straka |
courses:mapreduce-tutorial:perl-api [2012/01/23 21:28]
straka |
| sub cleanup { 1;} | sub cleanup { 1;} |
| </code> | </code> |
| * ''sub reduce($self, $key, $values, $context)'' -- executed for every (key, values) input data. | * ''sub reduce($self, $key, $values, $context)'' -- executed for every ''$key''. The ''$values'' is an iterator with the following methods: |
| * fsa | * ''$values%%->%%value()'' -- returns the current value, undef if there is any. |
| The variable '$content' has following methods: | * ''$values%%->%%next()'' -- advance to next value. Returns true if there is any, false otherwise. |
| | * At the beginning there is no current value, the first value should be obtained by calling 'next'. |
| | * ''sub reduce($self, $key, $values, $context)'' -- the variable '$content' has following methods: |
| * ''$content%%->%%write($key, $value)'' -- output the (''$key'', ''$value'') pair | * ''$content%%->%%write($key, $value)'' -- output the (''$key'', ''$value'') pair |
| * ''$content%%->%%counter($group, $name, $increment)'' -- increases the counter ''$name'' in the group ''$group'' by ''$increment'' | * ''$content%%->%%counter($group, $name, $increment)'' -- increases the counter ''$name'' in the group ''$group'' by ''$increment'' |
| * ''sub setup($self, $context)'' -- executed once before any input (key, values) pairs are processed. The ''$context'' can be used to both produce (key, value) pairs and increment counters. | * ''sub setup($self, $context)'' -- executed once before any input keys are processed. The ''$context'' can be used to both produce (key, value) pairs and increment counters. |
| * ''sub cleanup($self, $context)'' -- executed once after all input (key, values) pairs are processed. The ''$context'' can be used to both produce (key, value) pairs and increment counters. | * ''sub cleanup($self, $context)'' -- executed once after all input keys are processed. The ''$context'' can be used to both produce (key, value) pairs and increment counters. |
