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:file: This file is part of the pgRouting project.
:copyright: Copyright (c) 2018-2026 pgRouting developers
:license: Creative Commons Attribution-Share Alike 3.0 https://creativecommons.org/licenses/by-sa/3.0
.. index::
single: Traversal Family ; pgr_breadthFirstSearch - Experimental
single: Breadth First Search Category ; pgr_breadthFirstSearch - Experimental
single: breadthFirstSearch - Experimental on v3.0
|
``pgr_breadthFirstSearch`` - Experimental
===============================================================================
``pgr_breadthFirstSearch`` — Returns the traversal order(s) using Breadth First
Search algorithm.
.. include:: experimental.rst
:start-after: warning-begin
:end-before: end-warning
.. rubric:: Availability
.. rubric:: Version 4.0.0:
* Standardizing output columns to |result-spantree|
.. rubric:: Version 3.0.0
* New experimental function.
Description
-------------------------------------------------------------------------------
Provides the Breadth First Search traversal order from a root vertex to a
particular depth.
**The main Characteristics are:**
* The implementation will work on any type of graph.
* Provides the Breadth First Search traversal order from a source node to a
target depth level.
* Running time: :math:`O(E + V)`
|Boost| Boost Graph Inside
Signatures
-------------------------------------------------------------------------------
.. rubric:: Summary
.. admonition:: \ \
:class: signatures
| pgr_breadthFirstSearch(`Edges SQL`_, **root vid**, [**options**])
| pgr_breadthFirstSearch(`Edges SQL`_, **root vids**, [**options**])
| **options:** ``[max_depth, directed]``
| Returns set of |result-spantree|
.. index::
single: breadthFirstSearch - Experimental on v3.0 ; Single vertex - Experimental on v3.0
Single vertex
...............................................................................
.. admonition:: \ \
:class: signatures
| pgr_breadthFirstSearch(`Edges SQL`_, **root vid**, [**options**])
| **options:** ``[max_depth, directed]``
| Returns set of |result-spantree|
:Example: From root vertex :math:`6` on a **directed** graph with edges in
ascending order of ``id``
.. literalinclude:: breadthFirstSearch.queries
:start-after: -- q1
:end-before: -- q2
.. index::
single: breadthFirstSearch - Experimental on v3.0 ; Multiple vertices - Experimental on v3.0
Multiple vertices
...............................................................................
.. admonition:: \ \
:class: signatures
| pgr_breadthFirstSearch(`Edges SQL`_, **root vids**, [**options**])
| **options:** ``[max_depth, directed]``
| Returns set of |result-spantree|
:Example: From root vertices :math:`\{12, 6\}` on an **undirected** graph with
**depth** :math:`<= 2` and edges in ascending order of ``id``
.. literalinclude:: breadthFirstSearch.queries
:start-after: -- q2
:end-before: -- q3
Parameters
-------------------------------------------------------------------------------
.. include:: BFS-category.rst
:start-after: mst-bfs-dfs-params_start
:end-before: mst-bfs-dfs-params_end
Optional parameters
...............................................................................
.. include:: dijkstra-family.rst
:start-after: dijkstra_optionals_start
:end-before: dijkstra_optionals_end
DFS optional parameters
...............................................................................
.. include:: BFS-category.rst
:start-after: max-depth-optional-start
:end-before: max-depth-optional-end
Inner Queries
-------------------------------------------------------------------------------
Edges SQL
...............................................................................
.. include:: pgRouting-concepts.rst
:start-after: basic_edges_sql_start
:end-before: basic_edges_sql_end
Result columns
-------------------------------------------------------------------------------
.. include:: BFS-category.rst
:start-after: mst-bfs-dfs-dd-result-columns-start
:end-before: mst-bfs-dfs-dd-result-columns-end
Additional Examples
-------------------------------------------------------------------------------
:Example: Same as `Single vertex`_ with edges in ascending order of ``id``.
.. literalinclude:: breadthFirstSearch.queries
:start-after: -- q1
:end-before: -- q2
:Example: Same as `Single vertex`_ with edges in descending order of ``id``.
.. literalinclude:: breadthFirstSearch.queries
:start-after: -- q3
:end-before: -- q4
The resulting traversal is different.
The left image shows the result with ascending order of ids and the right image
shows with descending order of the edge identifiers.
|ascending| |descending|
.. |ascending| image:: images/bfs-ascending.png
:scale: 25%
.. |descending| image:: images/bfs-descending.png
:scale: 25%
See Also
-------------------------------------------------------------------------------
* :doc:`BFS-category`
* :doc:`sampledata`
* `Boost: Breadth First Search
<https://www.boost.org/libs/graph/doc/breadth_first_search.html>`__
* `Wikipedia: Breadth First Search algorithm
<https://en.wikipedia.org/wiki/Breadth-first_search>`__
.. rubric:: Indices and tables
* :ref:`genindex`
* :ref:`search`
|
