An adapter that takes in another RowIterator and produces the same rows, just in sorted order.
More...
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| SortingIterator (THD *thd, Filesort *filesort, unique_ptr_destroy_only< RowIterator > source, ha_rows num_rows_estimate, table_map tables_to_get_rowid_for, ha_rows *examined_rows) |
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| ~SortingIterator () override |
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bool | Init () override |
| Initialize or reinitialize the iterator. More...
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int | Read () override |
| Read a single row. More...
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void | SetNullRowFlag (bool is_null_row) override |
| Mark the current row buffer as containing a NULL row or not, so that if you read from it and the flag is true, you'll get only NULLs no matter what is actually in the buffer (typically some old leftover row). More...
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void | UnlockRow () override |
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void | CleanupAfterQuery () |
| Optional (when JOIN::destroy() runs, the iterator and its buffers will be cleaned up anyway); used to clean up the buffers a little bit earlier. More...
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const Filesort * | filesort () const |
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| RowIterator (THD *thd) |
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virtual | ~RowIterator ()=default |
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| RowIterator (const RowIterator &)=delete |
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| RowIterator (RowIterator &&)=default |
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virtual const IteratorProfiler * | GetProfiler () const |
| Get profiling data for this iterator (for 'EXPLAIN ANALYZE'). More...
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virtual void | SetOverrideProfiler ([[maybe_unused]] const IteratorProfiler *profiler) |
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virtual void | StartPSIBatchMode () |
| Start performance schema batch mode, if supported (otherwise ignored). More...
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virtual void | EndPSIBatchModeIfStarted () |
| Ends performance schema batch mode, if started. More...
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virtual RowIterator * | real_iterator () |
| If this iterator is wrapping a different iterator (e.g. More...
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virtual const RowIterator * | real_iterator () const |
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An adapter that takes in another RowIterator and produces the same rows, just in sorted order.
(The actual sort happens in Init().) Unfortunately, it is still bound to working off a TABLE object, which means that you can't use it to e.g. sort the output of a join without materializing into a temporary table first (ignoring that we currently have no Iterators for joins).
The primary reason for this is that we currently have no way of communicating read sets through Iterators, and SortingIterator needs to add fields used in ORDER BY to the read set for the appropriate tables. This could be mitigated by e.g. sending in an unordered_set<Field *>, but we don't currently have such a mechanism.
void SortingIterator::SetNullRowFlag |
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bool |
is_null_row | ) |
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overridevirtual |
Mark the current row buffer as containing a NULL row or not, so that if you read from it and the flag is true, you'll get only NULLs no matter what is actually in the buffer (typically some old leftover row).
This is used for outer joins, when an iterator hasn't produced any rows and we need to produce a NULL-complemented row. Init() or Read() won't necessarily reset this flag, so if you ever set is to true, make sure to also set it to false when needed.
Note that this can be called without Init() having been called first. For example, NestedLoopIterator can hit EOF immediately on the outer iterator, which means the inner iterator doesn't get an Init() call, but will still forward SetNullRowFlag to both inner and outer iterators.
TODO: We shouldn't need this. See the comments on AggregateIterator for a bit more discussion on abstracting out a row interface.
Implements RowIterator.