IndexedDB is a NoSQL database and requires no schema to pre-define. However to support query, object store must be indexed before querying. This is in fact, similar to defining query-able feed or COLUMN in SQL TABLE. For portability between IndexedDB and WebSQL, we define database schema are in JSON. Additionally the schema can be used to define relationship between stores, of which we discuss in other sections.

Database schema has the following fields:

database_schema = {
    version: 1, // optional, but recommended.
    size: 5 * 1024 * 1024, // 5 MB, optional estimated database size in byte
    stores: [store_schema] // list of store schema as array
}

Store schema is defined as:

store_schema = {
    name: 'store name',
    keyPath: 'id', // optional, can also be dotted path like 'entry.id.$t'
    autoIncrement: true, // optional. use when keyPath is not specified.
    indexes: [index_schema] // optional, list of index schema as array.
}

If keyPath is not defined, it will be automatically generated by the browser in IndexedDB and this wrapper will automatically generated for WebSQL.

Index schema is defined as:

index_schema = {
 name: 'field name',
 type: 'TEXT', // data type of the field, default to 'TEXT'
 unique: true
}