55 lines
1.6 KiB
ReStructuredText
55 lines
1.6 KiB
ReStructuredText
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Concepts
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========
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Things hopefully are straightforward but it's important to get the
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following straight in your head; the rest will come easier if you do.
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Source vs. Target
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-----------------
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Data always flows from source to target, it is the #1 rule.
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Docs and command output will always reflect this, e.g. **CSV →
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Wutta**.
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Source and target can be anything as long as the :term:`import
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handler` and :term:`importer(s) <importer>` implement the desired
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logic. The :term:`app database` is often involved but not always.
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Import vs. Export
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-----------------
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Surprise, there is no difference. After all from target's perspective
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everything is really an import.
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Sometimes it's more helpful to think of it as an export, e.g. **Wutta
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→ CSV** really seems like an export. In such cases the
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:attr:`~wuttasync.importing.handlers.ImportHandler.orientation` may be
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set to reflect the distinction.
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.. _import-handler-vs-importer:
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Import Handler vs. Importer
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---------------------------
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The :term:`import handler` is sort of the "wrapper" around one or more
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:term:`importers <importer>` and the latter contain the table-specific
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sync logic.
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In a DB or similar context, the import handler will make the
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connection, then invoke all requested importers, then commit
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transaction at the end (or rollback if dry-run).
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And each importer will read data from source, and usually also read
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data from target, then compare data sets and finally write data to
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target as needed. But each would usually do this for just one table.
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See also the base classes for each:
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* :class:`~wuttasync.importing.handlers.ImportHandler`
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* :class:`~wuttasync.importing.base.Importer`
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