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lookup transformation

原创 Linux操作系统 作者:ashleywzl 时间:2011-05-31 14:41:38 0 删除 编辑
  1. lookup transformation
    “L” denotes Lookup port
    “R” denotes port used as a return value (unconnected Lookup only)There can be only one return port

Usage
Get related values
Verify if records exists or  if data has changed(If a match is found, one or more table values are returned to the Mapping.  If no match is found, NULL is returned)

 

dynamic lookup cache
Update lookup cache with unfound or new lookup values.
Indicates with a numeric value whether the Integration Service inserts or updates the row in the cache, or makes no change to the cache

ignore null perperty
Ignore NULL values from input row and update the cache using only with non-NULL values from input

2.persisten caches
By default, Lookup caches are not persistent
When Session completes, cache is erased
Cache can be made persistent with the Lookup properties
When Session completes, the persistent cache is stored on the machine hard disk files
The next time Session runs, cached data is loaded fully or partially into RAM and reused
Can improve performance, but “stale” data may pose a problem
--how to cancel it

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