• 连接

警告：此功能处于测试阶段。请谨慎使用。

Manticore Search中的表连接允许您通过匹配相关列将两个表中的文档结合起来。此功能支持更复杂的查询，并增强了跨多个表的数据检索能力。

通用语法

SQL

SELECT
	select_expr [, select_expr] ...
	FROM tbl_name
	{INNER | LEFT} JOIN tbl2_name
	ON join_condition
	[...other select options]

join_condition: {
	left_table.attr = right_table.attr
	| left_table.json_attr.string_id = string(right_table.json_attr.string_id)
	| left_table.json_attr.int_id = int(right_table.json_attr.int_id)
}

有关选择选项的更多信息，请参阅 SELECT 部分。

当通过JSON属性的值进行连接时，您需要使用 int() 或 string() 函数显式指定值的类型。

SELECT ... ON left_table.json_attr.string_id = string(right_table.json_attr.string_id)

SELECT ... ON left_table.json_attr.int_id = int(right_table.json_attr.int_id)

JSON

POST /search
{
  "index": "table_name",
  "query": {
    <optional full-text query against the left table>
  },
  "join": [
    {
      "type": "inner" | "left",
      "table": "joined_table_name",
      "query": {
        <optional full-text query against the right table>
      },
      "on": [
        {
          "left": {
            "table": "left_table_name",
            "field": "field_name",
            "type": "<common field's type when joining using json attributes>"
          },
          "operator": "eq",
          "right": {
            "table": "right_table_name",
            "field": "field_name"
          }
        }
      ]
    }
  ],
  "options": {
    ...
  }
}

on.type: {
	int
	| string
}

请注意，在使用JSON属性连接两个表时，left 操作数部分中有一个 type 字段。允许的值为 string 和 int。

连接类型

Manticore Search 支持两种类型的连接：

1. INNER JOIN：仅返回两个表中都有匹配项的行。例如，该查询在 orders 和 customers 表之间执行一个 INNER JOIN，仅包含具有匹配客户的订单。

SELECT product, customers.email, customers.name, customers.address
FROM orders
INNER JOIN customers
ON customers.id = orders.customer_id
WHERE MATCH('maple', customers)
ORDER BY customers.email ASC;

POST /search
{
  "index": "orders",
  "join": [
    {
      "type": "inner",
      "table": "customers",
      "query": {
        "query_string": "maple"
      },
      "on": [
        {
          "left": {
            "table": "orders",
            "field": "customer_id"
          },
          "operator": "eq",
          "right": {
            "table": "customers",
            "field": "id"
          }
        }
      ]
    }
  ],
  "_source": ["product", "customers.email", "customers.name", "customers.address"],
  "sort": [{"customers.email": "asc"}]
}

+---------+-------------------+----------------+-------------------+
| product | customers.email   | customers.name | customers.address |
+---------+-------------------+----------------+-------------------+
| Laptop  | [e-mail] | Alice Johnson  | 123 Maple St      |
| Tablet  | [e-mail] | Alice Johnson  | 123 Maple St      |
+---------+-------------------+----------------+-------------------+
2 rows in set (0.00 sec)

{
  "took": 0,
  "timed_out": false,
  "hits": {
    "total": 2,
    "total_relation": "eq",
    "hits": [
      {
        "_id": 1,
        "_score": 1,
        "_source": {
          "product": "Laptop",
          "customers.email": "[e-mail]",
          "customers.name": "Alice Johnson",
          "customers.address": "123 Maple St"
        }
      },
      {
        "_id": 3,
        "_score": 1,
        "_source": {
          "product": "Tablet",
          "customers.email": "[e-mail]",
          "customers.name": "Alice Johnson",
          "customers.address": "123 Maple St"
        }
      }
    ]
  }
}

1. LEFT JOIN：返回左表中的所有行以及右表中匹配的行。如果没有匹配项，则右表的列返回 NULL 值。例如，该查询使用 LEFT JOIN 检索所有客户及其对应的订单。如果没有对应的订单，则会显示 NULL 值。结果按照客户的电子邮件进行排序，并且只选择客户的姓名和订单数量。

SELECT
name, orders.quantity
FROM customers
LEFT JOIN orders
ON orders.customer_id = customers.id
ORDER BY email ASC;

POST /search
{
	"index": "customers",
	"_source": ["name", "orders.quantity"],
	"join": [
    {
      "type": "left",
      "table": "orders",
      "on": [
        {
          "left": {
            "table": "orders",
            "field": "customer_id"
          },
          "operator": "eq",
          "right": {
            "table": "customers",
            "field": "id"
          }
        }
      ]
    }
  ],
  "sort": [{"email": "asc"}]
}

+---------------+-----------------+-------------------+
| name          | orders.quantity | @int_attr_email   |
+---------------+-----------------+-------------------+
| Alice Johnson |               1 | [e-mail] |
| Alice Johnson |               1 | [e-mail] |
| Bob Smith     |               2 | [e-mail]   |
| Carol White   |               1 | [e-mail] |
| John Smith    |            NULL | [e-mail]  |
+---------------+-----------------+-------------------+
5 rows in set (0.00 sec)

{
  "took": 0,
  "timed_out": false,
  "hits": {
    "total": 5,
    "total_relation": "eq",
    "hits": [
      {
        "_id": 1,
        "_score": 1,
        "_source": {
          "name": "Alice Johnson",
          "address": "123 Maple St",
          "email": "[e-mail]",
          "orders.id": 3,
          "orders.customer_id": 1,
          "orders.quantity": 1,
          "orders.order_date": "2023-01-03",
          "orders.tags": [
            101,
            104
          ],
          "orders.details": {
            "price": 450,
            "warranty": "1 year"
          },
          "orders.product": "Tablet"
        }
      },
      {
        "_id": 1,
        "_score": 1,
        "_source": {
          "name": "Alice Johnson",
          "address": "123 Maple St",
          "email": "[e-mail]",
          "orders.id": 1,
          "orders.customer_id": 1,
          "orders.quantity": 1,
          "orders.order_date": "2023-01-01",
          "orders.tags": [
            101,
            102
          ],
          "orders.details": {
            "price": 1200,
            "warranty": "2 years"
          },
          "orders.product": "Laptop"
        }
      },
      {
        "_id": 2,
        "_score": 1,
        "_source": {
          "name": "Bob Smith",
          "address": "456 Oak St",
          "email": "[e-mail]",
          "orders.id": 2,
          "orders.customer_id": 2,
          "orders.quantity": 2,
          "orders.order_date": "2023-01-02",
          "orders.tags": [
            103
          ],
          "orders.details": {
            "price": 800,
            "warranty": "1 year"
          },
          "orders.product": "Phone"
        }
      },
      {
        "_id": 3,
        "_score": 1,
        "_source": {
          "name": "Carol White",
          "address": "789 Pine St",
          "email": "[e-mail]",
          "orders.id": 4,
          "orders.customer_id": 3,
          "orders.quantity": 1,
          "orders.order_date": "2023-01-04",
          "orders.tags": [
            105
          ],
          "orders.details": {
            "price": 300,
            "warranty": "1 year"
          },
          "orders.product": "Monitor"
        }
      },
      {
        "_id": 4,
        "_score": 1,
        "_source": {
          "name": "John Smith",
          "address": "15 Barclays St",
          "email": "[e-mail]",
          "orders.id": 0,
          "orders.customer_id": 0,
          "orders.quantity": 0,
          "orders.order_date": "",
          "orders.tags": [],
          "orders.details": null,
          "orders.product": ""
        }
      }
    ]
  }
}

带有分面功能的复杂连接

此查询从 orders 和 customers 表中检索产品、客户姓名、产品价格和产品标签。它执行了一个 LEFT JOIN，确保即使客户没有下订单也会被包含在内。该查询过滤结果，仅包含价格大于 500 的订单，并将产品匹配为“laptop”、“phone”或“monitor”。结果按订单的 id 以升序排列。此外，查询还根据连接的 orders 表的 JSON 属性中的保修详情对结果进行分面处理。

SELECT orders.product, name, orders.details.price, orders.tags
FROM customers
LEFT JOIN orders
ON customers.id = orders.customer_id
WHERE orders.details.price > 500
AND MATCH('laptop|phone|monitor', orders)
ORDER BY orders.id ASC
FACET orders.details.warranty;

POST /search
{
  "index": "customers",
	"_source": ["orders.product", "name", "orders.details", "orders.tags"],
  "sort": [{"orders.id": "asc"}],
  "join": [
    {
      "type": "left",
      "table": "orders",
      "on": [
        {
          "left": {
            "table": "customers",
            "field": "id"
          },
          "operator": "eq",
          "right": {
            "table": "orders",
            "field": "customer_id"
          }
        }
      ],
      "query": {
        "range": {
          "orders.details.price": {
            "gt": 500
          }
        },
        "match": {
          "*": "laptop|phone|monitor"
        }
      }
    }
  ],
	"aggs":	{
		"group_property": {
			"terms": {
				"field": "orders.details.warranty"
			}
		}
	}
}

+----------------+---------------+----------------------+-------------+
| orders.product | name          | orders.details.price | orders.tags |
+----------------+---------------+----------------------+-------------+
| Laptop         | Alice Johnson |                 1200 | 101,102     |
| Phone          | Bob Smith     |                  800 | 103         |
+----------------+---------------+----------------------+-------------+
2 rows in set (0.01 sec)
--- 2 out of 2 results in 0ms ---

+-------------------------+----------+
| orders.details.warranty | count(*) |
+-------------------------+----------+
| 2 years                 |        1 |
| 1 year                  |        1 |
+-------------------------+----------+
2 rows in set (0.01 sec)
--- 2 out of 2 results in 0ms ---

{
  "took": 0,
  "timed_out": false,
  "hits": {
    "total": 2,
    "total_relation": "eq",
    "hits": [
      {
        "_id": 1,
        "_score": 1,
        "_source": {
          "name": "Alice Johnson",
          "orders.tags": [
            101,
            102
          ],
          "orders.details": {
            "price": 1200,
            "warranty": "2 years"
          },
          "orders.product": "Laptop"
        }
      },
      {
        "_id": 2,
        "_score": 1,
        "_source": {
          "name": "Bob Smith",
          "orders.tags": [
            103
          ],
          "orders.details": {
            "price": 800,
            "warranty": "1 year"
          },
          "orders.product": "Phone"
        }
      }
    ]
  },
  "aggregations": {
    "group_property": {
      "buckets": [
        {
          "key": "1 year",
          "doc_count": 1
        },
        {
          "key": "2 years",
          "doc_count": 1
        }
      ]
    }
  }
}

注意事项和最佳实践

在 Manticore Search 中使用 JOIN 时，请注意以下几点：

1. 字段选择：在 JOIN 中从两个表中选择字段时，不要为左表的字段加前缀，但要为右表的字段加前缀。例如：

   SELECT field_name, right_table.field_name FROM ...

2. JOIN 条件：在 JOIN 条件中始终显式指定表名：

   JOIN ON table_name.some_field = another_table_name.some_field

3. 带有 JOIN 的表达式：当使用结合两个连接表字段的表达式时，给表达式的结果起别名：

   SELECT *, (nums2.n + 3) AS x, x * n FROM nums LEFT JOIN nums2 ON nums2.id = nums.num2_id

4. 对别名表达式进行过滤：在 WHERE 子句中，不能对涉及两个表字段的表达式别名进行过滤。

5. 在 MVA 中使用 ANY：在 JOIN 中使用多值属性的 ANY() 函数时，为连接表中的多值属性起别名：

   SELECT *, t2.m AS alias
   FROM t
   LEFT JOIN t2 ON t.id = t2.t_id
   WHERE ANY(alias) IN (3, 5)

通过遵循这些指南，您可以有效地在 Manticore Search 中使用 JOIN 来结合多个索引的数据并执行复杂的查询。