composite_iterators.h File Reference

A composite row iterator is one that takes in one or more existing iterators and processes their rows in some interesting way. More...

#include <assert.h>
#include <stddef.h>
#include <stdint.h>
#include <sys/types.h>
#include <memory>
#include <string>
#include <utility>
#include <vector>
#include "my_alloc.h"
#include "my_base.h"
#include "my_inttypes.h"
#include "my_table_map.h"
#include "sql/iterators/row_iterator.h"
#include "sql/join_type.h"
#include "sql/mem_root_array.h"
#include "sql/pack_rows.h"
#include "sql/sql_array.h"
#include "sql_string.h"

Go to the source code of this file.

Classes
class	FilterIterator
	An iterator that takes in a stream of rows and passes through only those that meet some criteria (i.e., a condition evaluates to true). More...
class	LimitOffsetIterator
	Handles LIMIT and/or OFFSET; Init() eats the first "offset" rows, and Read() stops as soon as it's seen "limit" rows (including any skipped by offset). More...
class	AggregateIterator
	Handles aggregation (typically used for GROUP BY) for the case where the rows are already properly grouped coming in, ie., all rows that are supposed to be part of the same group are adjacent in the input stream. More...
class	NestedLoopIterator
	A simple nested loop join, taking in two iterators (left/outer and right/inner) and joining them together. More...
class	CacheInvalidatorIterator
	An iterator that helps invalidating caches. More...
struct	materialize_iterator::Operand
	An operand (query block) to be materialized by MaterializeIterator. More...
class	StreamingIterator
	StreamingIterator is a minimal version of MaterializeIterator that does not actually materialize; instead, every Read() just forwards the call to the subquery iterator and does the required copying from one set of fields to another. More...
class	MaterializedTableFunctionIterator
	An iterator that wraps a Table_function (e.g. More...
class	WeedoutIterator
	Like semijoin materialization, weedout works on the basic idea that a semijoin is just like an inner join as we long as we can get rid of the duplicates somehow. More...
class	RemoveDuplicatesIterator
	An iterator that removes consecutive rows that are the same according to a set of items (typically the join key), so-called “loose scan” (not to be confused with “loose index scan”, which is made by the range optimizer). More...
class	RemoveDuplicatesOnIndexIterator
	Much like RemoveDuplicatesIterator, but works on the basis of a given index (or more accurately, its keypart), not an arbitrary list of grouped fields. More...
class	NestedLoopSemiJoinWithDuplicateRemovalIterator
	An iterator that is semantically equivalent to a semijoin NestedLoopIterator immediately followed by a RemoveDuplicatesOnIndexIterator. More...
class	MaterializeInformationSchemaTableIterator
	MaterializeInformationSchemaTableIterator makes sure a given I_S temporary table is materialized (filled out) before we try to scan it. More...
class	AppendIterator
	Takes in two or more iterators and output rows from them sequentially (first all rows from the first one, the all from the second one, etc.). More...

Namespaces
namespace	materialize_iterator
namespace	temptable_aggregate_iterator

Functions
RowIterator *	materialize_iterator::CreateIterator (THD *thd, Mem_root_array< materialize_iterator::Operand > operands, const MaterializePathParameters *path_params, unique_ptr_destroy_only< RowIterator > table_iterator, JOIN *join)
	Create an iterator that materializes a set of row into a temporary table and sets up a (pre-existing) iterator to access that. More...
RowIterator *	temptable_aggregate_iterator::CreateIterator (THD *thd, unique_ptr_destroy_only< RowIterator > subquery_iterator, Temp_table_param *temp_table_param, TABLE *table, unique_ptr_destroy_only< RowIterator > table_iterator, JOIN *join, int ref_slice)
	Create an iterator that aggregates the output rows from another iterator into a temporary table and then sets up a (pre-existing) iterator to access the temporary table. More...

Detailed Description

A composite row iterator is one that takes in one or more existing iterators and processes their rows in some interesting way.

They are usually not bound to a single table or similar, but are the inner (non-leaf) nodes of the iterator execution tree. They consistently own their source iterator, although not its memory (since we never allocate row iterators on the heap–usually on a MEM_ROOT>). This means that in the end, you'll end up with a single root iterator which then owns everything else recursively.

SortingIterator and the two window iterators are also composite iterators, but are defined in their own files.