David Rowley <dgrowleyml@gmail.com>, 15 Tem 2024 Pzt, 14:38 tarihinde şunu yazdı:
On Sat, 13 Jul 2024 at 10:12, Melih Mutlu <m.melihmutlu@gmail.com> wrote: > I updated documentation for path and level columns and also fixed the tests as level starts from 1.
Thanks for updating.
+ The <structfield>path</structfield> column can be useful to build + parent/child relation between memory contexts. For example, the following + query calculates the total number of bytes used by a memory context and its + child contexts:
"a memory context" doesn't quite sound specific enough. Let's say what the query is doing exactly.
Changed "a memory context" with "CacheMemoryContext".
+<programlisting> +WITH memory_contexts AS ( + SELECT * + FROM pg_backend_memory_contexts +) +SELECT SUM(total_bytes) +FROM memory_contexts +WHERE ARRAY[(SELECT path[array_length(path, 1)] FROM memory_contexts WHERE name = 'CacheMemoryContext')] <@ path;
I don't think that example query is the most simple example. Isn't it better to use the most simple form possible to express that?
I think it would be nice to give an example of using "level" as an index into "path"
WITH c AS (SELECT * FROM pg_backend_memory_contexts) SELECT sum(c1.total_bytes) FROM c c1, c c2 WHERE c2.name = 'CacheMemoryContext' AND c1.path[c2.level] = c2.path[c2.level];
I changed the queries in the documentation and regression test to the ones similar to the above query that you shared.
+ /* + * Queue up all the child contexts of this level for the next + * iteration of the outer loop. + */
That outer loop is gone.
Removed that part.
Also, this was due to my hasty writing of the patch. I named the function get_memory_context_name_and_indent. I meant to write "ident". If we did get rid of the "parent" column, I'd not see any need to keep that function. The logic could just be put in PutMemoryContextsStatsTupleStore(). I just did it that way to avoid the repeat.
Fixed the name. Also I needed to cast parameters when calling that function as below to get rid of some warnings.