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HOLE stage v1.0 |
Pipelines v2.0 |
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Purpose, Operands, Streams used, Usage notes, Examples, See also |
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Syntax |
>>__HOLE_______________________________________________________________________________><
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Purpose |
Use the HOLE stage to read all input records and discard them. HOLE reads records from all of its connected input streams and does not write any records to any output stream. The HOLE stage terminates when all of its input streams have reached end-of-file.
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Operands |
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Streams used |
The following streams are used by the HOLE stage:
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Stream |
Action |
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Primary input stream |
HOLE reads records from all connected input streams.
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Primary output stream |
Although HOLE does not write any records to its primary output
stream, the output stream stays connected until all input streams have
reached end-of-file. |
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Usage notes |
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1) |
Delaying the records does not apply to
HOLE because it does not write any output records. |
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2) |
HOLE pulls
records through a pipeline when an earlier stage would otherwise end because
of receiving an end-of-file on its output stream. |
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3) |
HOLE verifies
that its secondary input and secondary output streams are not connected and
then begins execution. |
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Examples |
The following pipeline collates the two input files; master.txt and detail.txt , producing two output files; missing.txt and new.txt. The HOLE stage discards all its input records and only ends once it receives an end-of-file. This ensures that the COLLATE stage does not end prematurely.
**** Top of file ****01 Address Rxpipe0203 pipe (endchar ?),04 < c:\master.txt, /* Read master input file. */05 | sort, /* COLLATE expects a sorted input. */06 | c: collate, /* Find matches. */07 | hole, /* Discard matching records. */08 ?,09 < c:\detail.txt, /* Read detail input file. */10 | sort, /* COLLATE expects a sorted input. */11 | c:, /* Define secondary streams for COLLATE. */12 | > c:\missing.txt, /* Write missing records. */13 ?,14 c:, /* Define tertiary output for COLLATE. */15 | > c:\new.txt, /* Write new records. */16 ?,17 literal /Wait..collating./, /* Console info message. */18 | cons /* Write it to the console. */1920 Exit 0**** End of file ****