Data Pagination in Pipelines

In this section, we’ll explore how to paginate your data in Pipeline. We’ll use items model for this example.

var schema = {
    id: {
        type: NIMBUSDB_DATA_TYPE.INTEGER,
        const: NIMBUSDB_CONSTRAINT.PRIMARY_KEY
    },
    name: NIMBUSDB_DATA_TYPE.STRING,
    price: {
        type: NIMBUSDB_DATA_TYPE.NUMBER,
        validator: function(data, value) {
            return value >= 0;
        },
        default_value: 0
    },
    is_locked: {
        type: NIMBUSDB_DATA_TYPE.BOOLEAN,
        const: NIMBUSDB_CONSTRAINT.OPTIONAL,
        default_value: false
    }
};

items = new NimbusDBModel("global", "items", schema, [
    { id: 1, name: "Apple", price: 5 },
    { id: 2, name: "Banana", price: 7.2 },
    { id: 3, name: "Cherry", price: 15 },
    { id: 4, name: "Date", price: 12.5 },
    { id: 5, name: "Elderberry", price: 8 },
    { id: 6, name: "Fig", price: 10 },
    { id: 7, name: "Grape", price: 6 },
    { id: 8, name: "Honeydew", price: 9 },
    { id: 9, name: "Kiwi", price: 4 },
    { id: 10, name: "Lemon", price: 3 }
]);

Paginating Data

Limit Array

The limit operation is used to limit the data to the first _count elements. A negative value takes from the end.

// (1) limit to the first 3 elements
var items_pl = items.pipe()         // create an `items` pipeline
    // let's say you have this data in your pipeline:
    // [ 5, 7.2, 15, 12.5, 8, 10, 6, 9, 4, 3 ]
    .limit(3);            // limit to the first 3 elements

// result:
// [ 5, 7.2, 15 ]

// (2) limit to the last 3 elements
var items_pl = items.pipe()         // create an `items` pipeline
    // let's say you have this data in your pipeline:
    // [ 5, 7.2, 15, 12.5, 8, 10, 6, 9, 4, 3 ]
    .limit(-3);           // limit to the last 3 elements

// result:
// [ 3, 4, 9 ]

Offset Array

The offset operation is used to skip the first _count elements. A negative value skips from the end.

// (1) skip the first 3 elements
var items_pl = items.pipe()         // create an `items` pipeline
    // let's say you have this data in your pipeline:
    // [ 5, 7.2, 15, 12.5, 8, 10, 6, 9, 4, 3 ]
    .offset(3);           // skip the first 3 elements

// result:
// [ 12.5, 8, 10, 6, 9, 4, 3 ]

// (2) skip the last 3 elements
var items_pl = items.pipe()         // create an `items` pipeline
    // let's say you have this data in your pipeline:
    // [ 5, 7.2, 15, 12.5, 8, 10, 6, 9, 4, 3 ]
    .offset(-3);          // skip the last 2 elements (because `-1` is the last element)

// result:
// [ 9, 6, 10, 8, 12.5, 15, 7.2, 5 ]

Slice Array

The slice operation is used to extract a slice of the data starting at _start for _length elements.

// (1) extract a slice of the data starting at index 2
var items_pl = items.pipe()         // create an `items` pipeline
    // let's say you have this data in your pipeline:
    // [ 5, 7.2, 15, 12.5, 8, 10, 6, 9, 4, 3 ]
    .slice(2);          // start at index 2 (the third element) and extract remaining elements

// result:
// [ 15, 12.5, 8, 10, 6, 9, 4, 3 ]

// (2) extract a slice of the data starting at index 2 with a length of 2
var items_pl = items.pipe()         // create an `items` pipeline
    // let's say you have this data in your pipeline:
    // [ 5, 7.2, 15, 12.5, 8, 10, 6, 9, 4, 3 ]
    .slice(2, 3);       // start at index 2 (the third element) and extract 3 elements

// result:
// [ 15, 12.5, 8 ]

// (3) extract a slice of the data from the 3 last elements
var items_pl = items.pipe()         // create an `items` pipeline
    // let's say you have this data in your pipeline:
    // [ 5, 7.2, 15, 12.5, 8, 10, 6, 9, 4, 3 ]
    .slice(-3);         // start at the third-last element and extract remaining elements

// result:
// [ 9, 4, 3 ]

// (4) extract a slice of the data from the 3 last elements with a length of 2
var items_pl = items.pipe()         // create an `items` pipeline
    // let's say you have this data in your pipeline:
    // [ 5, 7.2, 15, 12.5, 8, 10, 6, 9, 4, 3 ]
    .slice(-3, 2);      // start at the third-last element and extract 2 elements

// result:
// [ 9, 4 ]

// (5) extract a slice of the data from the 3 last elements with a length of 4 (reversed)
var items_pl = items.pipe()         // create an `items` pipeline
    // let's say you have this data in your pipeline:
    // [ 5, 7.2, 15, 12.5, 8, 10, 6, 9, 4, 3 ]
    .slice(-3, -4);     // start at the third-last element and extract 4 elements (reversed)

// result:
// [ 9, 6, 10, 8 ]

References

Pipeline.limit()

Limits the pipeline data to the first _count elements. A negative value takes from the end.

Signature

class NimbusDBPipeline {
    // ... other methods and properties ...
    static limit(
        _count: int
    ): NimbusDBPipeline;
}

Parameters

`_count`

Type: int
The number of elements to keep. Negative values take from the end.

Returns

Type: NimbusDBPipeline
A new NimbusDBPipeline instance (mutable = false) or the current pipeline instance (mutable = true).

Pipeline.offset()

Skips the first _count elements. A negative value skips from the end.

Signature

class NimbusDBPipeline {
    // ... other methods and properties ...
    static offset(
        _count: int
    ): NimbusDBPipeline;
}

Parameters

`_count`

Type: int
The number of elements to skip.

Returns

Type: NimbusDBPipeline
A new NimbusDBPipeline instance (mutable = false) or the current pipeline instance (mutable = true).

Pipeline.slice()

Extracts a slice of the pipeline data starting at _start for _length elements.

Signature

class NimbusDBPipeline {
    // ... other methods and properties ...
    static slice(
        _start: int,
        _length?: int
    ): NimbusDBPipeline;
}

Parameters

`_start`

Type: int
The starting index (negative = from the end).

`_length`

Type: int
Default: undefined (data.length - start)
The number of elements to include.

Returns

Type: NimbusDBPipeline
A new NimbusDBPipeline instance (mutable = false) or the current pipeline instance (mutable = true).