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Diffstat (limited to 'doc/src/sgml/queries.sgml')
| -rw-r--r-- | doc/src/sgml/queries.sgml | 13 |
1 files changed, 12 insertions, 1 deletions
diff --git a/doc/src/sgml/queries.sgml b/doc/src/sgml/queries.sgml index c53c385365..bd3c3538c3 100644 --- a/doc/src/sgml/queries.sgml +++ b/doc/src/sgml/queries.sgml @@ -1681,6 +1681,15 @@ SELECT * FROM search_graph; </para> </tip> + <tip> + <para> + The recursive query evaluation algorithm produces its output in + breadth-first search order. You can display the results in depth-first + search order by making the outer query <literal>ORDER BY</> a + <quote>path</> column constructed in this way. + </para> + </tip> + <para> A helpful trick for testing queries when you are not certain if they might loop is to place a <literal>LIMIT</> @@ -1699,7 +1708,9 @@ SELECT n FROM t LIMIT 100; This works because <productname>PostgreSQL</productname>'s implementation evaluates only as many rows of a <literal>WITH</> query as are actually fetched by the parent query. Using this trick in production is not - recommended, because other systems might work differently. + recommended, because other systems might work differently. Also, it + usually won't work if you make the outer query sort the recursive query's + results or join them to some other table. </para> <para> |