N1ql Join and aggregate with additional values

N1QL
1

I have a single bucket (Couchbase Community edition 6.5) consisting of the following documents:

employees {
    employeeGroupId: string,
    type: "Employee"
}
clocks {
    employeeId: string,
    areaId: string
    date: string,
    type: "Clock"
}

Each employee has multiple corresponding clock items for each day. I need to get the following:

  1. first clock -> clockIn
  2. last clock -> clockOut

I have written the following query which gets the first and last clock items with execution time <100 ms:

SELECT META(employee).id AS employeeId,
       employee.employeeGroupId,
       MIN(clock.date) AS clockIn,
       MAX(clock.date) AS clockOut
FROM `bucket` employee LEFT
    JOIN `bucket` clock ON clock.employeeId = META(employee).id
    AND type = "Clock"
    AND clock.date BETWEEN "2020-06-01T00:00:00.000Z" AND "2020-06-02T00:00:00.000Z"
WHERE employee.type = "Employee"
GROUP BY employee;

The problem is I need to get the corresponding areaId with the matching clock.

I have written the following query that does. I create two separate sub queries that sort all of the clock items for the day first ascending and then descending and select the first item.

CREATE INDEX adv_employeeId_type_date_blockId ON `bucket`(`employeeId`,`type`,`date`,`blockId`)        
CREATE INDEX adv_employeeId_type_date ON `bucket`(`employeeId`,`type`,`date`)
CREATE INDEX adv_type_employeeId_date ON `bucket`(`type`,`employeeId`,`date`)

SELECT META(employee).id AS employeeId,
       employee.employeeGroupId,
       clockIn,
       clockOut
FROM `bucket` employee 
    LEFT JOIN (
    SELECT obj.employeeId,
           obj.date,
           obj.areaId
    FROM `bucket` obj
    WHERE obj.employeeId = META(employee).id
        AND obj.type = "Clock"
        AND obj.date BETWEEN "2020-06-01T00:00:00.000Z" AND "2020-06-02T00:00:00.000Z"
    ORDER BY obj.date
    LIMIT 1) clockIn ON clockIn.employeeId = META(employee).id 
    LEFT JOIN (
    SELECT obj.employeeId,
           obj.date,
           obj.areaId
    FROM `bucket` obj
    WHERE obj.employeeId = META(employee).id
        AND obj.type = "Clock"
        AND obj.date BETWEEN "2020-06-01T00:00:00.000Z" AND "2020-06-02T00:00:00.000Z"
    ORDER BY obj.date DESC
    LIMIT 1) clockOut ON clockOut.employeeId = META(employee).id
WHERE employee.type = "Employee"
GROUP BY employee,
         clockIn,
         clockOut;

The problem is that the above query is inefficient with execution time >10 seconds.

In other words I need to get additional object values from the aggregate MIN() and MAX() functions.

I am sure the second query is not the most efficient method to achieve this, does anyone have any other suggestions?

2 
CREATE INDEX ix1 ON `bucket`(type, `employeeGroupId`) WHERE type = "Employee";
CREATE INDEX ix2 ON `bucket`(`employeeId`, date, areaId) WHERE type = "Clock";

SELECT META(employee).id AS employeeId,
       employee.employeeGroupId,
       MIN([clock.date, {clock.date, clock.areaId}])[1] AS clockIn,
       MAX([clock.date, {clock.date, clock.areaId}])[1] AS clockOut,
FROM `bucket` AS employee LEFT
    JOIN `bucket` AS clock ON clock.employeeId = META(employee).id
    AND type = "Clock"
    AND clock.date BETWEEN "2020-06-01T00:00:00.000Z" AND "2020-06-02T00:00:00.000Z"
WHERE employee.type = "Employee"
GROUP BY employee;

Use MIN/MAX on Array. 0th expression on MIN/MAX. reset of array positions used only on ties (similar like ORDER BY multiple fields). Result will complete ARRAY expression. Choose which positions you want project. This technique allows you project non-group by expressions.

1 Like
3

Perfect! Thank you so much! This is exactly what I was looking for!

For future reference, here is the link to the stack overflow post: