Store

TypeScript Support

A read model store has an associated TypeScript type:

• Type Name - ResolveStore
• Package - @resolve-js/readmodel-base

The table below lists functions that you can use to communicate with a read model store through a store object.

Function Name	Description
defineTable	Defines a new table within the store.
find	Searches for data items.
findOne	Searches for a single data item.
count	Returns the number of items that meet a condition.
insert	Inserts an item into a table.
update	Updates data items.
delete	Deletes data items.

defineTable

Defines a new table within the store.

Arguments

Argument Name	Description
tableName	The new table's name.
tableDeclaration	An object that defines the new table's structure.

Example

Init: async store => {
  await store.defineTable('Stories', {
    indexes: { id: 'string', type: 'string' },
    fields: [
      'title',
      'text',
      'link',
      'commentCount',
      'votes',
      'createdAt',
      'createdBy',
      'createdByName'
    ]
  })

find

Searches for data items based on the specified expression.

Arguments

Argument Name	Description
tableName	A table name.
searchCondition	An object that defines a search expression.
projectionCondition	Defines which fields should be included into the resulting data sample.
sortCondition	Defines how to sort the resulting data sample.
skip	A number of data items to skip.
limit	The maximum number of data items to fetch.

Example

const getStories = async (type, store, { first, offset }) => {
  try {
    const search = type && type.constructor === String ? { type } : {}
    const skip = first || 0
    const stories = await store.find(
      'Stories',
      search,
      null,
      { createdAt: -1 },
      skip,
      offset
    )
    return Array.isArray(stories) ? stories : []
  } catch (error) {
    ...
    throw error
  }
}

The projection argument should be an object, in which keys are field names and values are either 1 or 0:

• 1 - specifies that the field should be included into the resulting data sample;
• 0 - specifies that a field should be excluded from the resulting sample.

The first field in a projection object defines how the projection is interpreted:

• If the first field's value is 1, the projection works in inclusive mode. In this mode, you only need to specify included fields. All omitted fields are excluded.
• If the first field's value is 0, the projection works in exclusive mode. In this mode, only excluded fields should be specified explicitly and all omitted fields are included.

Example

const findResult = await store.find(
  'TestTable',
  searchCondition,
  { field1: 1, field2: 1, field3: 1 }, // Return the specified fields
  //{ field1: 0, field2: 0, field3: 0 }, // Return all fields except for the specified fields
  { id: sortOrder },
  skip,
  limit
)

findOne

Searches for a data item based on the specified expression.

Arguments

Argument Name	Description
tableName	A table name.
searchCondition	An object that defines a search expression.
projectionCondition	Defines which fields should be included into the resulting data sample.

Example

[STORY_UPVOTED]: async (store, { aggregateId, payload: { userId } }) => {
  const story = await store.findOne(
    'Stories',
    { id: aggregateId },
    { votes: 1 }
  )
  await store.update(
    'Stories',
    { id: aggregateId },
    { $set: { votes: story.votes.concat(userId) } }
  )
},

count

Returns the number of items that meet the specified condition.

Arguments

Argument Name	Description
tableName	A table name.
searchCondition	An object that defines a search expression.

Example

const getStoryCount = async (type, store) =>
  const count = await store.count('Stories', {})
  return count
}

insert

Inserts an item into the specified table.

Arguments

Argument Name	Description
tableName	A table name.
document	An object that is an item to insert.

Example

[STORY_CREATED]: async (
    store, { aggregateId, timestamp, payload: { title, link, userId, userName, text } }
  ) => {
    const isAsk = link == null || link === ''
    const type = isAsk ? 'ask' : /^(Show HN)/.test(title) ? 'show' : 'story'

    const story = {
      id: aggregateId,
      type,
      title,
      text,
      link: !isAsk ? link : '',
      commentCount: 0,
      votes: [],
      createdAt: timestamp,
      createdBy: userId,
      createdByName: userName
    }

    await store.insert('Stories', story)
  },

update

Searches for data items and updates them based on the specified update expression.

Arguments

Argument Name	Description
tableName	The name of the table to update.
searchCondition	An object that defines a search expression.
updateCondition	An object that defines an update expression.
updateOptions	Specifies additional options for the update operation.

Example

[STORY_UPVOTED]: async (store, { aggregateId, payload: { userId } }) => {
  const story = await store.findOne(
    'Stories',
    { id: aggregateId },
    { votes: 1 }
  )
  await store.update(
    'Stories',
    { id: aggregateId },
    { $set: { votes: story.votes.concat(userId) } }
  )
},

delete

Deletes data items based on the specified search expression.

Arguments

Argument Name	Description
tableName	A table name.
searchCondition	An object that defines a search expression.

Example

[SHOPPING_LIST_REMOVED]: async (store, { aggregateId }) => {
  await store.delete('ShoppingLists', { id: aggregateId })
}

Search Expression Operators

Search expressions use operators to compare values and group expression clauses.

The following operators are supported:

Comparison operators:

Operator	Description
\$eq	Matches values that are equal to the specified value.
\$ne	Matches values that are not equal to the specified value.
\$lt	Matches values that are less than the specified value.
\$lte	Matches values that are less than or equal to the specified values.
\$gt	Matches values that are greater than the specified value.
\$gte	Matches values that are greater than or equal to the specified value.

Logical Operators:

Operator	Description
\$and	Joins two expressions with an AND operation.
\$or	Joins two expressions with an OR operation.
\$not	Applies a NOT operation to invert an expression.

Example

const data = await store.find('Entries', {
  $or: [
    { $and: [{ name: 'Second entry', id: 'id-2' }] },
    { $not: { id: { $gte: 'id-1' } } },
  ],
})