LINQ查询多个包含/任何的RavenDB [英] Linq query with multiple Contains/Any for RavenDB

问题描述

我有一个包含标签列表的文档类。是这样的：

I have a document class that contains a list of "tags". Something like:

class Item {
  string Name { get; set; }
  List<string> Tags {get; set;}
}

现在我想创造RavenDB一个查询，递给我所有资料的标签列表过滤。当使用实体框架，我设法通过这样的事情要做到这一点：

Now I would like to create a query for RavenDB that hands me all items filtered by a list of tags. When using Entity Framework I managed to do this by something like this:

var query = GetQueryable();
foreach (var tag in tags)
{
   query = query.Where(i => i.Tags.Contains(tag));
}

然而，这似乎

不RavenDB工作，很可能是因为包含不支持..我也尝试过使用任何重写，（其中（i => i.Tags.Any（T =>吨==标签））），但给了我一个奇怪的异常：

However, this doesn't seem to work with RavenDB, most likely because Contains isn't supported.. I've also tried rewriting it using Any, (Where(i => i.Tags.Any(t=>t == tag))) but that gives me a strange exception:

Unable to cast object of type
'System.Linq.Expressions.PrimitiveParameterExpression`1[System.String]'
to type 'System.Linq.Expressions.MemberExpression

任何伟大的想法？我做这完全错了。

Any great ideas? Am I doing this completely wrong?

推荐答案

包含确实​​尚不支持（或许是应该的，但是这完全是另一回事？ - 我们只有真正增加对各运营商的支持时，它的要求）

Contains is indeed not yet supported (Perhaps it should be, but that's another matter entirely - we only really add support for various operators when its asked for)

至于反对任何多个查询，我假设你正在试图做的动态数据，你想实现像

As for multiple queries against Any, I assume you're trying to do dynamic data and you want to achieve something like

"X OR Y OR Z"

这是一个棘手的，并拥有和，所以你的例子看起来像

That's a tricky one, and the LINQ provider by default will aggregate those multiple WHERE clauses with AND, so your example looks like

"X AND Y AND Z"

这显然会。从来没有出现这种情况。

Which will obviously never be the case.

这一个你最好的选择是下降到了Lucene查询（至少目前如此），做这样的事情：

Your best option for this one is to drop down to the Lucene query (at least for now) and do something like this:

var results = s.Advanced.LuceneQuery<Item>()
                   .Where(string.Format("Tags,:({0})", string.Join(" OR ", tags))); 

请有意义吗？

以上查询看起来像

"Tags,:(X OR Y OR Z)"

的注：标签，通知RavenDB的标签是一个数组的

好吧，！

让你真正的想最简单的方法的是做东西沿着这些路线

The easiest way to get what you actually want is to do something along these lines

                new IndexDefinition<Item, Item>()
                {
                    Map = docs => from doc in docs
                                  select new
                                  {
                                      Tags = doc.Tags
                                  },
                    Indexes = {{ x => x.Tags, FieldIndexing.Analyzed }}
                }.ToIndexDefinition(store.Conventions));

然后查询您的ANDS，你可以做这样的事情：

Then to query for your ands, you can do something like this:

                var results = s.Advanced.LuceneQuery<Item, WhateverYouCalledThatIndex>()
                   .Where(string.Format("Tags:({0})", string.Join(" AND ", tags)));

现在，事情需要注意的

       Tags = doc.Tags

将序列化整个阵列成一个巨大的一滴，因为它只是字符串，将在本例中工作。

Will serialize that entire array into one giant blob, as it's just strings that will work for this example.

我期待在表达这种更好的方法，这是不可能的，我们将拿出这样做，因为它并没有真正跨很好地映射的LINQ十岁上下的方式 - 但它的是的答案，将工作：）

I am looking at better ways of expressing this, it is unlikely that we'll come up with a LINQ-ish way of doing this, as it doesn't really map across very well - but it is an answer that will work :)

我想我会很希望能够至少做

I think I'd quite like to be able to at least do

  Map = docs => from doc in docs
                                  select new
                                  {
                                      Tags = String.Join(" ", doc.Tags)
                                  },

（这将无法工作，所以不要尝试），但它是一个比较明确你想要达到的。

(This won't work so don't try it), but it is a bit more explicit about what you want to achieve.

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