Syntax

db.createCollection(<name>,
   {
     timeseries: {
        timeField: <string>
     },
     rowStore: <boolean>
     shardKey: <document>
     sortKey: <document>
     indexes: <array>
     columns: <array>
     preserveJSONKeyOrder: <boolean>
     from: <document>
   }
)

{
  link: <string>
  database: <string>
  collection: <string>
}

The following options are not supported in a createCollection statement:

• capped

• timeseries.metaField

• timeseries.granularity

• clusteredIndex

• changeStreamPreAndPostImages

• size

• max

• storageEngine

• validator

• validationLevel

• validationAction

• indexOptionDefaults

• viewOn

• pipeline

• collation

• writeConcern

Unenforced Unique Keys

SingleStore allows you to create multiple "unenforced" unique indexes on collections created using the Kai API. Unenforced unique keys enable applications that create unique or unsupported indexes on collections to run on SingleStore without any code changes and enhance compatibility with existing MongoDB® applications.

Enable the uniqueUnenforced option to enable unenforced unique keys across the database as follows:

use <database>
db.runCommand({setDefaultCollectionOptions: 1, value: {uniqueUnenforced: true}})

Collections created after this option is enabled do not enforce the unique constraint, i.e. SingleStore does not block creation of multiple unique or unsupported indexes on a collection. Note that existing collections, created before this option is enabled, are not affected.

For example,

use dbTest;
db.createCollection("records",
   { rowStore: false }
);

// Create an index with a unique key, unsupported
db.records.createIndex(
  { unique_id: 1 }, { unique: true }
);

The unique key named: 'unique_id_1($unique_id)' cannot be created because unique keys must contain all columns of the shard key '($_id)'.

The createIndex command returns an error as shown in the output.

Now enable the uniqueUnenforced option, drop the records collection, and run the same commands again:

db.runCommand({setDefaultCollectionOptions: 1, value: {uniqueUnenforced: true}});

db.records.drop();

db.createCollection("records",
   { rowStore: false }
);

db.records.createIndex(
  { unique_id: 1 }, { unique: true }
);

Because unique indexes are now unenforced, this command runs successfully.

Examples

The following examples show how to use the createCollection command:

• Create a collection named exampleC with a field named Code:

  MongoDB

  Copy

  db.createCollection("exampleC", {
    columns: [{ id: "Code", type: "BIGINT NOT NULL" }],
  });

• Create a collection supported by a rowstore table:

  MongoDB

  Copy

  db.createCollection("exCollection", { rowstore: true });

• Replicate a collection dbTest.exampleC from a remote MongoDB® server defined using a link named lnkExample:

  MongoDB

  Copy

  use dbTest;
  db.createCollection("exampleC", { from: { link: "lnkExample" } });

  Refer to Replicate MongoDB® Collections to SingleStore for more information.

• Create a collection with column group enabled:

  MongoDB

  Copy

  db.createCollection("exampleCollection", { columnGroup: true });