Query Index in NoSQLAdmin Scope

You can query a NoSQL index and retrieve data by identifying the items using the primary keys of the index. Indexing allows you to execute alternate queries on the table data without making use of the primary keys of the main table.

You can configure indexes from the Catalyst console. You can use just the partition key or a combination of the partition key and sort key of the index to retrieve an item.

You can define the key condition that identifies the item by specifying the attributes, their required values, and the supported operator to be used. The supported operators are represented as shown below.

The following example code snippet details the following logic:

• The required query is executed by referring the required items using the index FruitIdentifier’s partition key fruitColor.
• The condition value is specified as “yellow”.
• The query is done using the queryIndex() SDK method.
• Implements consistent_read to indicate if the read operation must be done using the master or a slave cluster.
  • If the value is set as true, it is queried from the master.
  • If the value is set as false, it is queried from the slave.

const { NoSQLMarshall, NoSQLEnum } = require('zcatalyst-sdk-node/lib/no-sql');
const { NoSQLOperator } = NoSQLEnum;
// Query a NoSQL table index to fetch the items identified by the partition key fruitColor with the value "yellow"
const queriedIndexItems = await table.queryIndex('FruitIdentifier', {
  // Define the key condition to query the items with
  key_condition: {
    attribute: 'fruitColor',
    // Define the supported operator to be used
    operator: NoSQLOperator.EQUALS,
    value: NoSQLMarshall.makeString('yellow')
  },
  // Set consistent_read to true to query from master. If set to false, it is queried from slave.
  consistent_read: true,
  // Limit the number of rows to be returned by specifying a value
  limit: 15,
  // Set forward_scan to true to sort the results in ascending order. Otherwise, it is sorted in descending order.
  forward_scan: true
});