>From one of my followup posts:
Every scrap of documentation I've found says that GAE queries only
follow a single index (the one exception being zigzag merges, which
don't apply here). This means that to answer my query.filter(foo,
"fooValue1").sort("-bar"), there must be an index that contains the
foo and bar data sorted appropriately, no? Ie:
/Thing/foo:fooValue1/bar:bar9/[thekeyvalue]
/Thing/foo:fooValue1/bar:bar8/[thekeyvalue]
/Thing/foo:fooValue1/bar:bar7/[thekeyvalue]
/Thing/foo:fooValue2/bar:bar8/[thekeyvalue]
/Thing/foo:fooValue2/bar:bar7/[thekeyvalue]
To satisfy this query, GAE should start following this custom index
and that's pretty much it. There's no reason for it to touch the
single-property indexes (foo ASC, foo DESC, bar ASC, and bar DESC).
...and in my test, if I remove the custom index from
datastore-indexes.xml, it doesn't work. But also if I use
setUnindexedProperty, it doesn't work.
It's like setUnindexedProperty is being interpreted as "not only don't
set single-property indexes, but also don't include the property in
any custom indexes". This is counterintuitive - if I wanted the index
not to be built, I can just remove the index.
Jeff
On Thu, Mar 18, 2010 at 9:27 AM, Jeff Schnitzer <[email protected]> wrote:
> For those of you reading this thread on appengine-java, I apologize.
> However, I realized that this is really a general appengine question
> and might get a better response from someone "in the know" here.
> Here's the appengine-java thread:
>
> http://groups.google.com/group/google-appengine-java/browse_thread/thread/efed35cabf60f6ee
>
> ----------
>
> I'm puzzled by the behavior of custom indexes. I have a simple test
> case below, a simple equality filter on one property combined with a
> descending sort on another property. If I set the properties with
> setUnindexedProperty(), the query fails to find the result. If I set
> the properties with setProperty(), it does.
>
> Why? I have a custom index, therefore the query should not need or
> touch the single-property indexes on these fields, right?
>
> With this requirement, adding a single custom index means the
> datastore must now update (at least) five indexes on every put() - the
> single-value ASC and DESC indexes of both properties as well as my
> custom index. That's gotta hurt.
>
> Here's a test case using the low-level API:
>
> /** */
> @Test
> public void lowLevelTest() throws Exception
> {
> DatastoreService service =
> DatastoreServiceFactory.getDatastoreService();
>
> Entity ent = new Entity("Thing");
> ent.setUnindexedProperty("foo", "fooValue");
> ent.setUnindexedProperty("bar", 123L);
> // switching to this works
> //ent.setProperty("foo", "fooValue");
> //ent.setProperty("bar", 123L);
> service.put(ent);
>
> Query query = new Query("Thing");
> query.addFilter("foo", FilterOperator.EQUAL, "fooValue");
> query.addSort("bar", SortDirection.DESCENDING);
>
> PreparedQuery pq = service.prepare(query);
> int count = 0;
> for (Entity fetched: pq.asIterable())
> {
> count++;
> }
>
> assert count == 1;
> }
>
> The last assertion fails. The query doesn't find any results. The
> automatic datastore index seems to be fine:
>
> <!-- Indices written at Mon, 15 Mar 2010 21:49:01 PDT -->
> <datastore-indexes>
> <!-- Used 1 time in query history -->
> <datastore-index kind="Thing" ancestor="false" source="auto">
> <property name="foo" direction="asc"/>
> <property name="bar" direction="desc"/>
> </datastore-index>
> </datastore-indexes>
>
> What's up? Is this just a bug in the dev mode, or is there a real
> requirement that all properties must have single-value indexes in
> order to be part of a custom index?
>
> Thanks,
> Jeff
>
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