nexxai / electrodb

A dynamodb library to ease the use of having multiple entities and complex hierarchical relationships in one dynamodb table

ElectroDB

ElectroDB is a dynamodb library to ease the use of having multiple entities and complex heretical relationships in a single dynamodb table.

This library is a work in progress, please submit issues/feedback or reach out on twitter @tinkertamper.

Features

• Attribute Schema Enforcement: Define a schema for your entities with enforced attribute validation, defaults, types, aliases, and more.
• Easily Compose Hierarchical Access Patterns: Plan and design hierarchical keys for your indexes to multiply your possible access patterns.
• Single Table Entity Segregation: Entities created with ElectroDB will not conflict with other entities when using a single table.
• Simple Sort Key Condition Querying: Write efficient sort key queries by easily building compose keys.
• Simple Filter Composition: Easily create complex readable filters for Dynamo queries without worrying about the implementation of ExpressionAttributeNames, ExpressionAttributeValues.

Turn this:

let MallStores  =  new Entity(model,  client);
let mallId  =  "EastPointe";
let stateDate = "2020-04-01";
let endDate = "2020-07-01";
let maxRent = "5000.00";
let minRent = "2000.00";
let promotion = "1000.00";
let stores  =  MallStores.query
	.leases({ mallId })
	.between({ leaseEndDate:  stateDate }, { leaseEndDate:  endDate })
	.filter(({rent, discount}) => `
		${rent.between(minRent, maxRent)} AND ${discount.lte(promotion)}
	`)
	.params();

Into This:

{
  "IndexName": idx2',
  TableName: 'electro',
  ExpressionAttributeNames: {
    '#rent': 'rent',
    '#discount': 'discount',
    '#pk': 'idx2pk',
    '#sk1': 'idx2sk'
  },
  ExpressionAttributeValues: {
    ':rent1': '2000.00',
    ':rent2': '5000.00',
    ':discount1': '1000.00',
    ':pk': '$mallstoredirectory_1#mallid_eastpointe',
    ':sk1': '$mallstore#leaseenddate_2020-04-01#rent_',
    ':sk2': '$mallstore#leaseenddate_2020-07-01#rent_'
  },
  KeyConditionExpression: '#pk = :pk and #sk1 BETWEEN :sk1 AND :sk2',
  FilterExpression: '(#rent between :rent1 and :rent2) AND #discount <= :discount1'
}

Table of Contents

• ElectroDB
  • Features
• Table of Contents
• Installation
• Usage
  • Entities
  • Model
  • Attributes
  • Indexes
  • Facets
    • Facet Arrays
    • Facet Templates
  • Filters
    • Defined on the model
    • Defined via "Filter" method after query operators
    • Multiple Filters
• Building Queries - Sort Key Operations - Using facets to make hierarchical keys - Shopping Mall Stores
  • Query Chains
    • Get Method
    • Delete Method
    • Put Record
    • Update Record
    • Scan Records
    • Query Records
      • Partition Key Facets
  • Execute Query .go() and .params()
    • .params()
    • .go()
  • Query Chain Examples
  • Query Options
• Examples - Shopping Mall Property Management App - Shopping Mall Requirements
  • Access Patterns are accessible on the StoreLocation
    • PUT Record
      • Add a new Store to the Mall:
    • UPDATE Record
      • Change the Store's Lease Date:
    • GET Record
      • Retrieve a specific Store in a Mall
    • DELETE Record
      • Remove a Store location from the Mall
    • Query Records
      • Find Stores that match core access patterns
• Coming Soon:

Installation

Install from NPM

npm install electrodb --save

Usage

Unlike in traditional sql databases, a single DynamoDB table will include multiple entities along side each other. Additionally, DynamoDB utilizes Partition and Sort Keys to query records to allow for hierarchical relationships. ElectroDB allows you to make the most of these concepts with less headaches.

Entities

In ElectroDB an Entity is a single record that represents a single business object. For example, in a simple contact application, one entity could represent a Person and another entity might represent a Contact method for that person (email, phone, etc.).

Require or import Entity from electrodb:

const {Entity} = require("electrodb");

Model

Create an Entity's schema

const  DynamoDB  =  require("aws-sdk/clients/dynamodb");
const {Entity} = require("electrodb");
const client = new DynamoDB.DocumentClient();

let model = {  
	service: "ClientRelationshipApp", 
	entity: "UserContacts", 
	table: "ClientContactTable", 
	version: "1", 
	attributes: {
		clientId: {
			type: "string",
			required: true,
		},            
		userId: {  
			type: "string", 
			required: true,  
		},
		type: { 
			type: ["email", "phone", "social"], 
			required: true,
		},
		value:  {
			type: "string", 
			required: true,
		},
		canContactWeekends: {
			type: "boolean",
			required: false
		},
		maxContactFrequency: {
			type: "number",
			required: true,
			default: 5
		}
	},
	indexes: {
		contact: {
			pk: {
				field: "PK",
				facets: ["value"]
			},
			sk: {
				field: "SK",
				facets: ["clientId", "userId"]
			}
		},
		clientContact: {
			index: "GSI1PK-GSI1SK-Index",
			pk: {
				field: "GSI1PK",
				facets: ["clientId"]
			},
			sk: {
				field: "GSI1SK",
				facets: ["value", "userId"]
			}
		},
		userContact: {
			index: "GSI2PK-GSI2SK-Index",
			pk: {
				field: "GSI2PK",
				facets: ["userId"]
			},
			sk: {
				field: "GSI2SK",
				facets: ["userId", "value"]
			}
		}
	},
	filters: {
		weekendFrequency: (attributes, max, canContact) => {
			let {maxContactFrequency, canContactWeekends} = attributes;
			return ` 
				${maxContactFrequency.lte(max)} AND ${canContactWeekends.eq(canContact)} 
			`
		}
 	}  
};

const UserContacts = new Entity(model, {client});

Property	Description
service	Name of the application using the entity, used to namespace all entities
entity	Name of the entity that the schema represents
table	Name of the dynamodb table in aws
version	(optional) The version number of the schema, used to namespace keys
attributes	An object containing each attribute that makes up the schema
indexes	An object containing table indexes, including the values for the table's default Partition Key and Sort Key
filters	An object containing user defined filter template functions.

Attributes

Attributes define an Entity record. The propertyName represents the value your code will use to represent an attribute.

Pro-Tip: Using the field property, you can map an AttributeName to a different field name in your table. This can be useful to utilize existing tables, existing models, or even to reduce record sizes via shorter field names.

attributes: {
	<AttributeName>: {
		"type": <string|string[]>,
		"required": [boolean],
		"default": [value|() => value]
		"validate": [RegExp|() => boolean]
		"field": [string]
		"readOnly": [boolean]
		"label": [string]
		"cast": ["number"|"string"|"boolean"],
		"get": (attribute, schema) => value,
		"set": (attribute, schema) => value 
	}
}

Property	Type	Required	Description
type	string, string[]	yes	Accepts the values: "string", "number" "boolean", or an array of strings representing a finite list of acceptable values: ["option1", "option2", "option3"].
required	boolean	no	Whether or not the value is required when creating a new record.
default	value, () => value	no	Either the default value itself or a synchronous function that returns the desired value.
validate	RegExp, () => boolean	no	Either regex or a synchronous callback to return a boolean.
field	string	no	The name of the attribute as it exists dynamo, if named differently in the schema attributes. Defaults to the AttributeName as defined in the schema.
readOnly	boolean	no	Prevents update of the property after the record has been created. Attributes used in the composition of the table's primary Partition Key and Sort Key are by read-only by default.
label	string	no	Used in index composition to prefix key facets. By default, the AttributeName is used as the label.
cast	"number", "string", "boolean"	no	Optionally cast attribute values when interacting with DynamoDB. Current options include: "number", "string", and "boolean".
set	(attribute, schema) => value	no	A synchronous callback allowing you apply changes to a value before it is set in params or applied to the database. First value represents the value passed to ElectroDB, second value are the attributes passed on that update/put
get	(attribute, schema) => value	no	A synchronous callback allowing you apply changes to a value after it is retrieved from the database. First value represents the value passed to ElectroDB, second value are the attributes retrieved from the database.

Indexes

The indexes object requires at least the definition of the table's natural Partition Key and (if applicable) Sort Key.

Indexes are defined, and later referenced by their accessPatternName. These defined via a facets array that is made up of attributes names as listed the model.

indexes: {
	<accessPatternName>: {
		"pk": {
			"field": <string>
			"facets": <AttributeName[]>
		},
		"sk": {
			"field": <string>
			"facets": <AttributesName[]>
		},
		"index": [string]
	}
}

Property	Type	Required	Description
pk	object	yes	Configuration for the pk of that index or table
pk.facets	boolean	no	An array that represents the order in which attributes are concatenated to facets the key (see Facets below for more on this functionality).
pk.field	string	yes	The name of the attribute as it exists dynamo, if named differently in the schema attributes.
sk	object	no	Configuration for the sk of that index or table
sk.facets	`array	string`	no
sk.field	string	yes	The name of the attribute as it exists dynamo, if named differently in the schema attributes.
index	string	yes	Used only when the Index defined is a Global Secondary Index; this is left blank for the table's primary index.

Facets

A Facet is a segment of a key based on one of the attributes. Facets are concatenated together from either a Partition Key or an Sort Key key, which define an index.

There are two ways to provide facets:

1. As a Facet Array
2. As a Facet Template

For example, in the following Access Pattern, "locations" is made up of the facets storeId, mallId, buildingId and unitId which map to defined attributes in the schema:

// Input
{
    storeId: "STOREVALUE",
    mallId: "MALLVALUE",
    buildingId: "BUILDINGVALUE",
    unitId: "UNITVALUE"
};

// Output:
{
	pk: '$mallstoredirectory_1#storeId_storevalue',
	sk: '$mallstores#mallid_mallvalue#buildingid_buildingvalue#unitid_unitvalue'
}

For PK values, the service and version values from the model are prefixed onto the key.

For SK values, the entity value from the model is prefixed onto the key.

Facet Arrays

In a Facet Array, each element is the name of the corresponding Attribute defined in the Model. If the Attribute has a label property, that will be used to prefix the facets, otherwise the full Attribute name will be used.

attributes: {
	storeId: {
		type: "string",
		label: "sid",
	},
	mallId: {
		type: "string",
		label: "mid",
	},
	buildingId: {
		type: "string",
		label: "bid",
	},
	unitId: {
		type: "string",
		label: "uid",
	}
},
indexes: {
	locations: {
		pk: {
			field: "pk",
			facets: ["storeId"]
		},
		sk: {
			field: "sk",
			facets: ["mallId", "buildingId", "unitId"]
		}
	}
}
    
// Input
{
    storeId: "STOREVALUE",
    mallId: "MALLVALUE",
    buildingId: "BUILDINGVALUE",
    unitId: "UNITVALUE"
};

// Output:
{
	pk: '$mallstoredirectory_1#sid_storevalue',
	sk: '$mallstores#mid_mallvalue#bid_buildingvalue#uid_unitvalue'
}

Facet Templates

In a Facet Template, you provide a formatted template for ElectroDB to use when making keys.

The syntax to a Facet Template is simple using the following rules: 1. Only alphanumeric, underscore, colons, and hash symbols are valid. the following regex is used to determine validity: /^[A-Z1-9:#_]+$/gi 2. Attributes are identified by a prefixed colon and the attributes name. For example, the syntax :storeId will matches storeId attribute in the model 3. Convention for a composing a key use the # symbol to separate attributes, and for labels to attach with underscore. For example, when composing both the mallId and buildingId would be expressed as mid_:mallId#bid_:buildingId.

attributes: {
	storeId: {
		type: "string"
	},
	mallId: {
		type: "string"
	},
	buildingId: {
		type: "string"
	},
	unitId: {
		type: "string"
	}
},
indexes: {
	locations: {
		pk: {
			field: "pk",
			facets: "sid_:storeId"
		},
		sk: {
			field: "sk",
			facets: "mid_:mallId#bid_:buildingId#uid_:unitId"
		}
	}
}


// Input
{
    storeId: "STOREVALUE",
    mallId: "MALLVALUE",
    buildingId: "BUILDINGVALUE",
    unitId: "UNITVALUE"
};

// Output:
{
	pk: '$mallstoredirectory_1#sid_storevalue',
	sk: '$mallstores#mid_mallvalue#bid_buildingvalue#uid_unitvalue'
}

Filters

Building thoughtful indexes can make queries simple and performant. Sometimes you need to filter results down further. By adding Filters to your model, you can extend your queries with custom filters. Below is the traditional way you would add a filter to Dynamo's DocumentClient directly along side how you would accomplish the same using a Filter function.

{
  IndexName: 'idx2',
  TableName: 'electro',
  ExpressionAttributeNames: {
    '#rent': 'rent',
    '#discount': 'discount',
    '#pk': 'idx2pk',
    '#sk1': 'idx2sk'
  },
  ExpressionAttributeValues: {
    ':rent1': '2000.00',
    ':rent2': '5000.00',
    ':discount1': '1000.00',
    ':pk': '$mallstoredirectory_1#mallid_eastpointe',
    ':sk1': '$mallstore#leaseenddate_2020-04-01#rent_',
    ':sk2': '$mallstore#leaseenddate_2020-07-01#rent_'
  },
  KeyConditionExpression: '#pk = :pk and #sk1 BETWEEN :sk1 AND :sk2',
  FilterExpression: '(#rent between :rent1 and :rent2) AND #discount <= :discount1'
}

Defined on the model

/**
	* Filter by low rent a specific mall or a leaseEnd withing a specific range  
	* @param {Object} attributes - All attributes from the model with methods for each filter operation  
	* @param {...*} values - Values passed when calling the filter in a query chain.
**/
filters: {
	rentPromotions: function(attributes, minRent, maxRent, promotion)  {
		let {rent, discount} = attributes;
		return `
			${rent.between(minRent, maxRent)} AND ${discount.lte(promotion)}
		`
	}
}


let MallStores  =  new Entity(model,  client);
let mallId  =  "EastPointe";
let stateDate = "2020-04-01";
let endDate = "2020-07-01";
let maxRent = "5000.00";
let minRent = "2000.00";
let promotion = "1000.00";
let stores  =  MallStores.query
	.stores({ mallId })
	.between({ leaseEndDate:  stateDate }, { leaseEndDate:  endDate })
	.rentPromotions(minRent, maxRent, promotion)
	.params();

// Results
{
  IndexName: 'idx2',
  TableName: 'electro',
  ExpressionAttributeNames: {
    '#rent': 'rent',
    '#discount': 'discount',
    '#pk': 'idx2pk',
    '#sk1': 'idx2sk'
  },
  ExpressionAttributeValues: {
    ':rent1': '2000.00',
    ':rent2': '5000.00',
    ':discount1': '1000.00',
    ':pk': '$mallstoredirectory_1#mallid_eastpointe',
    ':sk1': '$mallstore#leaseenddate_2020-04-01#rent_',
    ':sk2': '$mallstore#leaseenddate_2020-07-01#rent_'
  },
  KeyConditionExpression: '#pk = :pk and #sk1 BETWEEN :sk1 AND :sk2',
  FilterExpression: '(#rent between :rent1 and :rent2) AND #discount <= :discount1'
}

Defined via "Filter" method after query operators

let MallStores  =  new Entity(model,  client);
let mallId  =  "EastPointe";
let stateDate = "2020-04-01";
let endDate = "2020-07-01";
let maxRent = "5000.00";
let minRent = "2000.00";
let promotion = "1000.00";
let stores  =  MallStores.query
	.leases({ mallId })
	.between({ leaseEndDate:  stateDate }, { leaseEndDate:  endDate })
	.filter(({rent, discount}) => `
		${rent.between(minRent, maxRent)} AND ${discount.lte(promotion)}
	`)
	.params();

// Results
{
  IndexName: 'idx2',
  TableName: 'electro',
  ExpressionAttributeNames: {
    '#rent': 'rent',
    '#discount': 'discount',
    '#pk': 'idx2pk',
    '#sk1': 'idx2sk'
  },
  ExpressionAttributeValues: {
    ':rent1': '2000.00',
    ':rent2': '5000.00',
    ':discount1': '1000.00',
    ':pk': '$mallstoredirectory_1#mallid_eastpointe',
    ':sk1': '$mallstore#leaseenddate_2020-04-01#rent_',
    ':sk2': '$mallstore#leaseenddate_2020-07-01#rent_'
  },
  KeyConditionExpression: '#pk = :pk and #sk1 BETWEEN :sk1 AND :sk2',
  FilterExpression: '(#rent between :rent1 and :rent2) AND #discount <= :discount1'
}

Filter functions allow you to write a FilterExpression without having to worry about the complexities of expression attributes. To accomplish this, ElectroDB injects an object attributes as the first parameter to all Filter Functions. This object contains every Attribute defined in the Entity's Model with the following operators as methods:

operator	example	result
gte	rent.gte(maxRent)	#rent >= :rent1
gt	rent.gt(maxRent)	#rent > :rent1
lte	rent.lte(maxRent)	#rent <= :rent1
lt	rent.lt(maxRent)	#rent < :rent1
eq	rent.eq(maxRent)	#rent = :rent1
begins	rent.begins(maxRent)	begins_with(#rent, :rent1)
exists	rent.exists(maxRent)	exists(#rent = :rent1)
notExists	rent.notExists(maxRent)	not exists(#rent = :rent1)
contains	rent.contains(maxRent)	contains(#rent = :rent1)
notContains	rent.notContains(maxRent)	not contains(#rent = :rent1)
between	rent.between(minRent, maxRent)	(#rent between :rent1 and :rent2)

This functionality allows you to write the remaining logic of your FilterExpression with ease. Add complex nested and/or conditions or other FilterExpression logic while ElectroDB handles the ExpressionAttributeNames and ExpressionAttributeValues.

Multiple Filters

It is possible to include chain multiple filters. The resulting FilterExpressions are concatinated with an implicit AND operator.

let MallStores = new Entity(model, client);
let mallId = "EastPointe";
let stateDate = "2020-04-01";
let endDate = "2020-07-01";
let maxRent = "5000.00";
let minRent = "2000.00";
let promotion = "1000.00";
let stores = MallStores.query
	.leases({ mallId })
	.between({ leaseEndDate: stateDate }, { leaseEndDate: endDate })
	.filter(({ rent, discount }) => `
		${rent.between(minRent, maxRent)} AND ${discount.eq(promotion)}
	`)
	.filter(({ category }) => `
		${category.eq("food/coffee")}
	`)
	.params();

// Results
{
  TableName: 'StoreDirectory',
  ExpressionAttributeNames: {
    '#rent': 'rent',
    '#discount': 'discount',
    '#category': 'category',
    '#pk': 'idx2pk',
    '#sk1': 'idx2sk'
  },
  ExpressionAttributeValues: {
    ':rent1': '2000.00',
    ':rent2': '5000.00',
    ':discount1': '1000.00',
    ':category1': 'food/coffee',
    ':pk': '$mallstoredirectory_1#mallid_eastpointe',
    ':sk1': '$mallstore#leaseenddate_2020-04-01#storeid_',
    ':sk2': '$mallstore#leaseenddate_2020-07-01#storeid_'
  },
  KeyConditionExpression: '#pk = :pk and #sk1 BETWEEN :sk1 AND :sk2',
  IndexName: 'idx2',
  FilterExpression: '(#rent between :rent1 and :rent2) AND (#discount = :discount1 AND #category = :category1)'
}

Building Queries

Forming a composite Partition Key and Sort Key is a critical step in planning Access Patterns in DynamoDB. When planning composite keys, it is critical to consider the order in which they are composed. As of the time of writing this documentation, DynamoDB has the following constraints that should be taken into account when planning your Access Patterns:

1. You must always supply the Partition Key in full for all queries to DynamoDB.
2. You currently only have the following operators available on a Sort Key: begins_with, between, >, >=, <, <=, and Equals.
3. To act on single record, you will need to know the full Partition Key and Sort Key for that record.

Sort Key Operations

operator	use case
begins_with	Keys starting with a particular set of characters.
between	Keys between a specified range.
eq	Keys equal to some value
gt	Keys less than some value
gte	Keys less than or equal to some value
lt	Keys greater than some value
lte	Keys greater than or equal to some value

Using facets to make hierarchical keys

Carefully considering your Facet order will allow *ElectroDB to express hierarchical relationships and unlock more available Access Patterns for your application.

For example, let's say you have a MallStore Entity that represents Store Locations inside Malls:

Shopping Mall Stores

let model = {  
	service: "MallStoreDirectory",  
	entity: "MallStore",  
	table: "StoreDirectory",  
	version: "1",  
	attributes: {  
		mallId: {  
			type: "string",  
			required: true,  
		},  
		storeId: {  
			type: "string",  
			required: true,  
		},  
		buildingId: {  
			type: "string",  
			required: true,  
		},  
		unitId: {  
			type: "string",  
			required: true,
		},  
		category: {  
			type: [
				"spite store",
				"food/coffee", 
				"food/meal", 
				"clothing", 
				"electronics", 
				"department", 
				"misc"
			],  
			required: true  
		},  
		leaseEndDate: {  
			type: "string",  
			required: true  
		},
		rent: {
			type: "string",
			required: true,
			validate: /^(\d+\.\d{2})$/
		},
		discount: {
			type: "string",
			required: false,
			default: "0.00",
			validate: /^(\d+\.\d{2})$/
		}  
	},  
	indexes: {  
	    stores: {  
			pk: {
				field: "pk",
				facets: ["storeId"]
			}, 
			sk: {
				field: "sk",
				facets: ["mallId", "buildingId", "unitId"]
			}  
		},  
		malls: {  
			index: "idx1",  
			pk: {
				field: "idx1pk",
				facets: ["mallId"]
			},  
			sk: {
				field: "idx1sk",
				facets: ["buildingId", "unitId", "storeId"]
			}  
		},
		leases: {
			index: "idx2",
			pk: {
				field: "idx2pk",
				facets: ["mallId"]
			},  
			sk: {
				field: "idx2pk",
				facets: ["leaseEndDate", "storeId", "buildingId", "unitId"]
			}  
		}
	},
	filters: {
		byCategory: ({category}, name) => category.eq(name),
		rentDiscount: (attributes, discount, max, min) => {
			return `${attributes.discount.lte(discount)} AND ${attributes.rent.between(max, min)}`
		}
	}  
};

Each record represents one Store location. All Stores are located in Malls we manage.

To satisfy requirements for searching based on location, you could use the following keys: Each MallStore record would have a Partition Key with the store's storeId. This key alone is not enough to identify a particular store. To solve this, compose a Sort Key for the store's location attribute ordered hierarchically (mall/building/unit): ["mallId", "buildingId", "unitId"].

The MallStore entity above, using just the stores Index alone enables four Access Patterns:

1. All LatteLarrys locations in all Malls
2. All LatteLarrys locations in one Mall
3. All LatteLarrys locations inside a specific Mall
4. A specific LatteLarrys inside of a Mall and Building

Query Chains

Queries in ElectroDB are built around the Access Patterns defined in the Schema and are capable of using partial key Facets to create performant lookups. To accomplish this, ElectroDB offers a predictable chainable API.

Examples in this section using the MallStore schema defined above.

The methods: Get (get), Create (put), Update (update), and Delete (delete) *require all facets described in the Entities' primary PK and SK.

Get Method

Provide all facets in an object to the get method

let storeId = "LatteLarrys";
let mallId = "EastPointe";
let buildingId = "BuildingA1";
let unitId = "B47";
await StoreLocations.get({storeId, mallId, buildingId, unitId}).go();

Delete Method

Provide all facets in an object to the delete method to delete a record.

let storeId = "LatteLarrys";
let mallId = "EastPointe";
let buildingId = "BuildingA1";
let unitId = "B47";
await StoreLocations.delete({storeId, mallId, buildingId, unitId}).go();

Put Record

Provide all required Attributes as defined in the model to create a new record. ElectroDB will enforce any defined validations, defaults, casting, and field aliasing.

let store = {
	storeId: "LatteLarrys",
	mallId: "EastPointe",
	buildingId: "BuildingA1",
	unitId: "B47",
	category: "food/coffee",
	leaseEndDate: "2020-03-22"
}
await StoreLocations.put(store).go();

Update Record

To update a record, pass all facets to the update method and then pass set attributes that need to be updated.

Note: If your update includes changes to an attribute that is also a facet for a global secondary index, you must provide all facets for that index.

let storeId = "LatteLarrys";
let mallId = "EastPointe";
let buildingId = "BuildingA1";
let unitId = "B47";
let category = "food/meal";
await StoreLocations
	.update({storeId, mallId, buildingId, unitId})
	.set({category})
	.go();

Scan Records

When scanning for rows, you can use filters the same as you would any query. For more detial on filters, see the Filters section.

Note: Scan functionality will be scoped to your Entity. This means your results will only include records that match the Entity defined in the model.

await StoreLocations.scan
	.filter(({category}) => `
		${category.eq("food/coffee")} OR ${category.eq("spite store")}  
	`)
	.filter(({leaseEndDate}) => `
		${leaseEndDate.between("2020-03", "2020-04")}
	`)
	.go();

Query Records

Examples in this section using the MallStore schema defined above.

All queries start from the Access Pattern defined in the schema.

const MallStore = new Entity(schema); 
// Each Access Pattern is available on the Entity instance
// MallStore.query.stores()
// MallStore.query.malls()

Partition Key Facets

All queries require (at minimum) the Facets included in its defined Partition Key. They can be supplied in the order they are composed or in a single object when invoking the Access Pattern.

const MallStore = new Entity(schema);
//	stores
//	pk: ["storeId"]
//	sk: ["mallId", "buildingId", "unitId"]

let storeId = "LatteLarrys";
let mallId = "EastPointe";

// Good: As an object
MallStore.query.stores({storeId});

// Bad: Facets missing, will throw
MallStore.query.stores(); // err: Params passed to ENTITY method, must only include storeId

// Bad: Facets not included, will throw
MallStore.query.stores({mallId}); // err: Params passed to ENTITY method, must only include storeId

After invoking the Access Pattern with the required Partition Key Facets, you can now choose what Sort Key Facets are applicable to your query. Examine the table in Sort Key Operations for more information on the available operations on a Sort Key.

Execute Query .go() and .params()

Lastly, all query chains end with either a .go() or a .params() method invocation. These will either execute the query to DynamoDB (.go()) or return formatted parameters for use with the DynamoDB docClient (.params()).

Both .params() and .go() take a query configuration object which is detailed more in the section Query Options.

.params()

The params method ends a query chain, and synchronously formats your query into an object ready for the DynamoDB docClient.

For more information on the options available in the config object, checkout the section Query Options.

let config = {};
let stores = MallStores.query
    .leases({ mallId })
    .between(
      { leaseEndDate:  "2020-06-01" }, 
      { leaseEndDate:  "2020-07-31" })
    .filter(attr) => attr.rent.lte("5000.00"))
    .params(config);

// Results:
{
  IndexName: 'idx2',
  TableName: 'electro',
  ExpressionAttributeNames: { '#rent': 'rent', '#pk': 'idx2pk', '#sk1': 'idx2sk' },
  ExpressionAttributeValues: {
    ':rent1': '5000.00',
    ':pk': '$mallstoredirectory_1#mallid_eastpointe',
    ':sk1': '$mallstore#leaseenddate_2020-06-01#rent_',
    ':sk2': '$mallstore#leaseenddate_2020-07-31#rent_'
  },
  KeyConditionExpression: '#pk = :pk and #sk1 BETWEEN :sk1 AND :sk2',
  FilterExpression: '#rent <= :rent1'
}

.go()

The go method ends a query chain, and asynchronously queries DynamoDB with the client provided in the model.

For more information on the options available in the config object, check out the section Query Options.

let config = {};
let stores  =  MallStores.query
				.leases({ mallId })
				.between(
					{ leaseEndDate:  "2020-06-01" }, 
					{ leaseEndDate:  "2020-07-31" })
				.filter(({rent}) => rent.lte("5000.00"))
				.go(config);

Query Chain Examples

Below are all chain possibilities available, given the MallStore model.

// leases  
// pk: ["mallId"]  
// sk: ["buildingId", "unitId", "storeId"]

let mallId = "EastPointe";

// begins_with
MallStore.query.leases({mallId}).go()
MallStore.query.leases({mallId, leaseEndDate: "2020-03"}}).go();
MallStore.query.leases({mallId, leaseEndDate: "2020-03-22", rent: "2000.00"}).go();

// gt, gte, lt, lte
MallStore.query.leases({mallId}).gt({leaseEndDate}).go();
MallStore.query.leases({mallId}).gte({leaseEndDate}).go();
MallStore.query.leases({mallId}).lt({leaseEndDate}).go();
MallStore.query.leases({mallId}).lte({leaseEndDate}).go();

// between
MallStore.query.leases({mallId}).between({leaseEndDate: "2020-03"}, {leaseEndDate: "2020-04"}).go();

// filters -- applied after any of the sort key operators above 
let june = "2020-06";
let july = "2020-07"; 
let discount = "500.00";
let maxRent = "2000.00";
let minRent = "5000.00";

MallStore.query
  .leases({mallId, leaseEndDate: june})
  .rentDiscount(discount, maxRent, minRent)
  .go();

MallStore.query
  .leases({mallId})
  .between(
    {leaseEndDate: june}, 
    {leaseEndDate: july})
  .byCategory("food/coffee")
  .go();

Query Options

By default ElectroDB enables you to work with records as the names and properties defined in the model. Additionally, it removes the need to deal directly with the docClient parameters which can be complex for a team without as much experience with DynamoDB. The Query Options object can be passed to both the .params() and .go() methods when building you query. Below are the options available:

let options = {
	params: [object],
	raw: [boolean],
	includeKeys: [boolean],
	originalErr: [boolean],
};

Option	Description
params	Properties added to this object will be merged onto the params sent to the document client. Any conflicts with ElectroDB will favor the params specified here.
raw	Returns query results as they were returned by the docClient.
includeKeys	By default, ElectroDB does not return partition, sort, or global keys in its response.
originalErr	By default, ElectroDB alters the stacktrace of any exceptions thrown by the DynamoDB client to give better visibility to the developer. Set this value equal to true to turn off this functionality and return the error unchanged.

Examples

Shopping Mall Property Management App

For an example, lets look at the needs of application used to manage Shopping Mall properties. The application assists employees in the day-to-day operations of multiple Shopping Malls.

Shopping Mall Requirements

1. As a Maintenance Worker I need to know which stores are currently in each Mall down to the Building they are located.
2. As a Helpdesk Employee I need to locate related stores in Mall locations by Store Category.
3. As a Property Manager I need to identify upcoming leases in need of renewal.

Create a new Entity using the MallStore schema defined above

const DynamoDB = require("aws-sdk/clients/dynamodb");
const client = new DynamoDB.DocumentClient();
const MallStore = new Entity(model, {client});

Access Patterns are accessible on the StoreLocation

PUT Record

Add a new Store to the Mall:

await MallStore.create({
	mallId: "EastPointe",
	storeId: "LatteLarrys",
	buildingId: "BuildingA1",
	unitId: "B47",
	category: "spite store",
	leaseEndDate: "2020-02-29",
	rent: "5000.00",
}).go();

Returns the following:

{
	"mallId": "EastPointe",
	"storeId": "LatteLarrys",
	"buildingId": "BuildingA1",
	"unitId": "B47",
	"category": "spite store",
	"leaseEndDate": "2020-02-29",
	"rent": "5000.00",
	"discount": "0.00",
}

---

UPDATE Record

Change the Store's Lease Date:

When updating a record, you must include all Facets associated with the table's primary PK and SK.

let storeId = "LatteLarrys";
let mallId = "EastPointe";
let buildingId = "BuildingA1";
let unitId = "B47";
await StoreLocations.update({storeId, mallId, buildingId, unitId}).set({
	leaseEndDate: "2021-02-28"
}).go();

Returns the following:

{
	"leaseEndDate": "2021-02-28"
}

GET Record

Retrieve a specific Store in a Mall

When retrieving a specific record, you must include all Facets associated with the table's primary PK and SK.

let storeId = "LatteLarrys";
let mallId = "EastPointe";
let buildingId = "BuildingA1";
let unitId = "B47";
await StoreLocations.get({storeId, mallId, buildingId, unitId}).go();

Returns the following:

{
	"mallId": "EastPointe",
	"storeId": "LatteLarrys",
	"buildingId": "BuildingA1",
	"unitId": "B47",
	"category": "spite store",
	"leaseEndDate": "2021-02-28",
	"rent": "5000.00",
	"discount": "0.00"
}

DELETE Record

Remove a Store location from the Mall

When removing a specific record, you must include all Facets associated with the table's primary PK and SK.

let storeId = "LatteLarrys";
let mallId = "EastPointe";
let buildingId = "BuildingA1";
let unitId = "B47";
let storeId = "LatteLarrys";
await StoreLocations.delete({storeId, mallId, buildingId, unitId}).go();

Returns the following:

{}

Query Records

Find Stores that match core access patterns

All Stores in a particular mall (Requirement #1)

let mallId = "EastPointe";
let stores = await StoreLocations.malls({mallId}).query().go();

All Stores in a particular mall building (Requirement #1)

let mallId = "EastPointe";
let buildingId = "BuildingA1";
let stores = await StoreLocations.malls({mallId}).query({buildingId}).go();

What store is located in unit "B47"? (Requirement #1)

let mallId = "EastPointe";
let buildingId = "BuildingA1";
let unitId = "B47";
let stores = await StoreLocations.malls({mallId}).query({buildingId, unitId}).go();

Stores by Category at Mall (Requirement #2)

let mallId = "EastPointe";
let category = "food/coffee";
let stores = await StoreLocations.malls({mallId}).byCategory(category).go();

Stores by upcoming lease (Requirement #3)

let mallId = "EastPointe";
let q2StartDate = "2020-04-01";
let stores = await StoreLocations.leases({mallId}).lt({leaseEndDate: q2StateDate}).go();

Stores will renewals for Q4 (Requirement #3)

let mallId = "EastPointe";
let q4StartDate = "2020-10-01";
let q4EndDate = "2020-12-31";
let stores = await StoreLocations.leases(mallId)
    .between (
      {leaseEndDate: q4StartDate}, 
      {leaseEndDate: q4EndDate})
    .go();

Spite-stores with release renewals this year (Requirement #3)

let mallId = "EastPointe";
let yearStarDate = "2020-01-01";
let yearEndDate = "2020-12-31";
let storeId = "LatteLarrys";
let stores = await StoreLocations.leases(mallId)
    .between (
      {leaseEndDate: yearStarDate}, 
      {leaseEndDate: yearEndDate})
    .filter(attr => attr.category.eq("Spite Store"))
    .go();

All Latte Larry's in a particular mall building (crazy for any store except a coffee shop)

let mallId = "EastPointe";
let buildingId = "BuildingA1";
let unitId = "B47";
let storeId = "LatteLarrys";
let stores = await StoreLocations.malls({mallId}).query({buildingId, storeId}).go();

Coming Soon:

• Collection class for relating and querying across multiple entities, configuring/enforcing relationships
• .page() finish method (like .params() and .go()) to allow for easier pagination of results
• Additional query options like limit, pages, attributes, sort and more for easier querying.
• Default query options defined on the model to give more general control of interactions with the Entity.