组合查询

组合查询表达式

组合查询是多种查询类型的组合，例如：

您可以使用逻辑查询运算符来组合数字、标签和文本字段的查询表达式。对于向量字段，您可以将 KNN 查询与预过滤器结合使用。

注意：
运算符的解释略有不同，具体取决于所使用的查询方言。默认方言为DIALECT 1;有关如何更改 Dialect 版本的信息，请参阅此文章。本文使用查询方言的第二个版本，DIALECT 2，并使用其他方括号 （(...)） 以帮助阐明示例。更多详细信息可以在 Query syntax documentation 中找到。

本文中的示例使用以下架构：

字段名称 字段类型
description TEXT
condition TAG
price NUMERIC
vector VECTOR

和

二元运算符 （space） 用于使两个或多个表达式的结果相交。 

FT.SEARCH index "(expr1) (expr2)"

如果要根据特定文本字段中的多个值执行交集，则应使用以下简化的概念：

FT.SEARCH index "@text_field:( value1 value2 ... )"

以下示例显示了一个查询，该查询查找处于新状况且价格范围从 500 USD 到 1000 USD 的自行车：

You might also be interested in bicycles for kids. The query below shows you how to combine a full-text search with the criteria from the previous query:

OR

You can use the binary operator | (vertical bar) to perform a union.

FT.SEARCH index "(expr1) | (expr2)"
Note:
The logical AND takes precedence over OR when using dialect version two. The expression expr1 expr2 | expr3 expr4 means (expr1 expr2) | (expr3 expr4). Version one of the query dialect behaves differently. Using parentheses in query strings is advised to ensure the order is clear.

If you want to perform the union based on multiple values within a single tag or text field, then you should use the following simplified notion:

FT.SEARCH index "@text_field:( value1 | value2 | ... )"

FT.SEARCH index "@tag_field:{ value1 | value2 | ... }"

The following query shows you how to find used bicycles that contain either the word 'kids' or 'small':

The previous query searches across all text fields. The following example shows you how to limit the search to the description field:

If you want to extend the search to new bicycles, then the below example shows you how to do that:

NOT

A minus (-) in front of a query expression negates the expression.

FT.SEARCH index "-(expr)"

If you want to exclude new bicycles from the search within the previous price range, you can use this query:

Numeric filter

The FT.SEARCH command allows you to combine any query expression with a numeric filter.

FT.SEARCH index "expr" FILTER numeric_field start end

Please see the range query article to learn more about numeric range queries and such filters.

Pre-filter for a KNN vector query

You can use a simple or more complex query expression with logical operators as a pre-filter in a KNN vector query.

FT.SEARCH index "(filter_expr)=>[KNN num_neighbours @field $vector]" PARAMS 2 vector "binary_data" DIALECT 2

Here is an example:

The vector search article provides further details about vector queries in general.

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