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Delta Sharing Protocol

Overview

Delta Sharing is an open protocol for secure real-time exchange of large datasets, which enables secure data sharing across products for the first time. It is a simple REST protocol that securely shares access to part of a cloud dataset. It leverages modern cloud storage systems, such as S3, ADLS, or GCS, to reliably transfer large datasets.

With Delta Sharing, the user accessing shared data can directly connect to it through Pandas, Tableau, or dozens of other systems that implement the open protocol, without having to deploy a specific platform first. This reduces their access time from months to minutes, and makes life dramatically simpler for data providers who want to reach as many users as possible.

This document is a specification for the Delta Sharing Protocol, which defines the REST APIs and the formats of messages used by any clients and servers to exchange data.

Delta Sharing Specification

Concepts

  • Share: A share is a logical grouping to share with recipients. A share can be shared with one or multiple recipients. A recipient can access all resources in a share. A share may contain multiple schemas.
  • Schema: A schema is a logical grouping of tables. A schema may contain multiple tables.
  • Table: A table is a Delta Lake table or a view on top of a Delta Lake table.
  • Recipient: A principal that has a bearer token to access shared tables.
  • Sharing Server: A server that implements this protocol.

REST APIs

Here are the list of APIs used by Delta Sharing Protocol. All of the REST APIs use bearer tokens for authorization. The {prefix} of each API is configurable, and servers hosted by different providers may pick up different prefixes.

List Shares

This is the API to list shares accessible to a recipient.

HTTP Request Value
Method GET
Header Authorization: Bearer {token}
URL {prefix}/shares
Query Parameters maxResults (type: Int32, optional): The maximum number of results per page that should be returned. If the number of available results is larger than maxResults, the response will provide a nextPageToken that can be used to get the next page of results in subsequent list requests. The server may return fewer than maxResults items even if there are more available. The client should check nextPageToken in the response to determine if there are more available. Must be non-negative. 0 will return no results but nextPageToken may be populated.

pageToken (type: String, optional): Specifies a page token to use. Set pageToken to the nextPageToken returned by a previous list request to get the next page of results. nextPageToken will not be returned in a response if there are no more results available.
200: The shares were successfully returned.
HTTP Response Value
Header

Content-Type: application/json; charset=utf-8
Body 
{
  "items": [
    {
      "name": "string",
      "id": "string"
    }
  ],
  "nextPageToken": "string"
}

Note: the items field may be an empty array or missing when no results are found. The client must handle both cases.

Note: the id field is optional. If id is populated for a share, its value should be unique across the sharing server and stay immutable through the share's lifecycle. The format recommendation of id is UUID.

Note: the nextPageToken field may be an empty string or missing when there are no additional results. The client must handle both cases.
400: The request is malformed.
HTTP Response Value
Header

Content-Type: application/json
Body 
{
  "errorCode": "string",
  "message": "string"
}
401: The request is unauthenticated. The bearer token is missing or incorrect.
HTTP Response Value
Header

Content-Type: application/json
Body 
{
  "errorCode": "string",
  "message": "string"
}
403: The request is forbidden from being fulfilled.
HTTP Response Value
Header

Content-Type: application/json
Body 
{
  "errorCode": "string",
  "message": "string"
}
500: The request is not handled correctly due to a server error.
HTTP Response Value
Header

Content-Type: application/json
Body 
{
  "errorCode": "string",
  "message": "string"
}

Example:

GET {prefix}/shares?maxResults=10&pageToken=...

{
   "items": [
      {
         "name": "vaccine_share",
         "id": "edacc4a7-6600-4fbb-85f3-a62a5ce6761f"   
      },
      {
         "name": "sales_share",
         "id": "3e979c79-6399-4dac-bcf8-54e268f48515"
      }
   ],
   "nextPageToken": "..."
}

Get Share

This is the API to get the metadata of a share.

HTTP Request Value
Method GET
Header Authorization: Bearer {token}
URL {prefix}/shares/{share}
URL Parameters {share}: The share name to query. It's case-insensitive.
200: The share's metadata was successfully returned.
HTTP Response Value
Header

Content-Type: application/json; charset=utf-8
Body 
{
  "share": {
    "name": "string",
    "id": "string"
  }
}

Note: the id field is optional. If id is populated for a share, its value should be unique across the sharing server and stay immutable through the share's lifecycle. The format recommendation of id is UUID.
400: The request is malformed.
HTTP Response Value
Header

Content-Type: application/json
Body 
{
  "errorCode": "string",
  "message": "string"
}
401: The request is unauthenticated. The bearer token is missing or incorrect.
HTTP Response Value
Header

Content-Type: application/json
Body 
{
  "errorCode": "string",
  "message": "string"
}
403: The request is forbidden from being fulfilled.
HTTP Response Value
Header

Content-Type: application/json
Body 
{
  "errorCode": "string",
  "message": "string"
}
404: The requested resource does not exist.
HTTP Response Value
Header

Content-Type: application/json
Body 
{
  "errorCode": "string",
  "message": "string"
}
500: The request is not handled correctly due to a server error.
HTTP Response Value
Header

Content-Type: application/json
Body 
{
  "errorCode": "string",
  "message": "string"
}

Example:

GET {prefix}/shares/vaccine_share

{
  "share": {
    "name": "vaccine_share",
    "id": "edacc4a7-6600-4fbb-85f3-a62a5ce6761f"
  }
}

List Schemas in a Share

This is the API to list schemas in a share.

HTTP Request Value
Method GET
Header Authorization: Bearer {token}
URL {prefix}/shares/{share}/schemas
URL Parameters {share}: The share name to query. It's case-insensitive.
Query Parameters maxResults (type: Int32, optional): The maximum number of results per page that should be returned. If the number of available results is larger than maxResults, the response will provide a nextPageToken that can be used to get the next page of results in subsequent list requests. The server may return fewer than maxResults items even if there are more available. The client should check nextPageToken in the response to determine if there are more available. Must be non-negative. 0 will return no results but nextPageToken may be populated.

pageToken (type: String, optional): Specifies a page token to use. Set pageToken to the nextPageToken returned by a previous list request to get the next page of results. nextPageToken will not be returned in a response if there are no more results available.
200: The schemas were successfully returned.
HTTP Response Value
Header

Content-Type: application/json; charset=utf-8
Body 
{
  "items": [
    {
      "name": "string",
      "share": "string"
    }
  ],
  "nextPageToken": "string"
}

Note: the items field may be an empty array or missing when no results are found. The client must handle both cases.

Note: the nextPageToken field may be an empty string or missing when there are no additional results. The client must handle both cases.
400: The request is malformed.
HTTP Response Value
Header

Content-Type: application/json
Body 
{
  "errorCode": "string",
  "message": "string"
}
401: The request is unauthenticated. The bearer token is missing or incorrect.
HTTP Response Value
Header

Content-Type: application/json
Body 
{
  "errorCode": "string",
  "message": "string"
}
403: The request is forbidden from being fulfilled.
HTTP Response Value
Header

Content-Type: application/json
Body 
{
  "errorCode": "string",
  "message": "string"
}
404: The requested resource does not exist.
HTTP Response Value
Header

Content-Type: application/json
Body 
{
  "errorCode": "string",
  "message": "string"
}
500: The request is not handled correctly due to a server error.
HTTP Response Value
Header

Content-Type: application/json
Body 
{
  "errorCode": "string",
  "message": "string"
}

Example:

GET {prefix}/shares/vaccine_share/schemas?maxResults=10&pageToken=...

{
  "items": [
    {
      "name": "acme_vaccine_data",
      "share": "vaccine_share"
    }
  ],
  "nextPageToken": "..."
}

List Tables in a Schema

This is the API to list tables in a schema.

HTTP Request Value
Method GET
Header Authorization: Bearer {token}
URL {prefix}/shares/{share}/schemas/{schema}/tables
URL Parameters {share}: The share name to query. It's case-insensitive.
{schema}: The schema name to query. It's case-insensitive.
Query Parameters maxResults (type: Int32, optional): The maximum number of results per page that should be returned. If the number of available results is larger than maxResults, the response will provide a nextPageToken that can be used to get the next page of results in subsequent list requests. The server may return fewer than maxResults items even if there are more available. The client should check nextPageToken in the response to determine if there are more available. Must be non-negative. 0 will return no results but nextPageToken may be populated.

pageToken (type: String, optional): Specifies a page token to use. Set pageToken to the nextPageToken returned by a previous list request to get the next page of results. nextPageToken will not be returned in a response if there are no more results available.
200: The tables were successfully returned.
HTTP Response Value
Header

Content-Type: application/json; charset=utf-8
Body 
{
  "items": [
    {
      "name": "string",
      "schema": "string",
      "share": "string",
      "shareId": "string",
      "id": "string"
    }
  ],
  "nextPageToken": "string"
}

Note: the items field may be an empty array or missing when no results are found. The client must handle both cases.

Note: the id field is optional. If id is populated for a table, its value should be unique within the share and stay immutable through the table's lifecycle. The format recommendation of id is UUID.

Note: the shareId field is optional. If shareId is populated for a table, its value should be unique across the sharing server and immutable through the table's lifecycle.

Note: the nextPageToken field may be an empty string or missing when there are no additional results. The client must handle both cases.
400: The request is malformed.
HTTP Response Value
Header

Content-Type: application/json
Body 
{
  "errorCode": "string",
  "message": "string"
}
401: The request is unauthenticated. The bearer token is missing or incorrect.
HTTP Response Value
Header

Content-Type: application/json
Body 
{
  "errorCode": "string",
  "message": "string"
}
403: The request is forbidden from being fulfilled.
HTTP Response Value
Header

Content-Type: application/json
Body 
{
  "errorCode": "string",
  "message": "string"
}
404: The requested resource does not exist.
HTTP Response Value
Header

Content-Type: application/json
Body 
{
  "errorCode": "string",
  "message": "string"
}
500: The request is not handled correctly due to a server error.
HTTP Response Value
Header

Content-Type: application/json
Body 
{
  "errorCode": "string",
  "message": "string"
}

Example:

GET {prefix}/shares/vaccine_share/schemas/acme_vaccine_data/tables?maxResults=10&pageToken=...

{
  "items" : [
    {
      "share" : "vaccine_share",
      "schema" : "acme_vaccine_data",
      "name" : "vaccine_ingredients",
      "shareId": "edacc4a7-6600-4fbb-85f3-a62a5ce6761f",
      "id": "dcb1e680-7da4-4041-9be8-88aff508d001"
    },
    {
      "share" : "vaccine_share",
      "schema" : "acme_vaccine_data",
      "name" : "vaccine_patients",
      "shareId": "edacc4a7-6600-4fbb-85f3-a62a5ce6761f",
      "id": "c48f3e19-2c29-4ea3-b6f7-3899e53338fa"
    }
  ],
  "nextPageToken" : "..."
}

List all Tables in a Share

This is the API to list all the tables under all schemas in a share.

HTTP Request Value
Method GET
Header Authorization: Bearer {token}
URL {prefix}/shares/{share}/all-tables
URL Parameters {share}: The share name to query. It's case-insensitive.
Query Parameters maxResults (type: Int32, optional): The maximum number of results per page that should be returned. If the number of available results is larger than maxResults, the response will provide a nextPageToken that can be used to get the next page of results in subsequent list requests. The server may return fewer than maxResults items even if there are more available. The client should check nextPageToken in the response to determine if there are more available. Must be non-negative. 0 will return no results but nextPageToken may be populated.

pageToken (type: String, optional): Specifies a page token to use. Set pageToken to the nextPageToken returned by a previous list request to get the next page of results. nextPageToken will not be returned in a response if there are no more results available.
200: The tables were successfully returned.
HTTP Response Value
Header

Content-Type: application/json; charset=utf-8
Body 
{
  "items": [
    {
      "name": "string",
      "schema": "string",
      "share": "string",
      "shareId": "string",
      "id": "string"
    }
  ],
  "nextPageToken": "string"
}

Note: the items field may be an empty array or missing when no results are found. The client must handle both cases.

Note: the id field is optional. If id is populated for a table, its value should be unique within the share and stay immutable through the table's lifecycle. The format recommendation of id is UUID.

Note: the shareId field is optional. If shareId is populated for a table, its value should be unique across the sharing server and immutable through the table's lifecycle.

Note: the nextPageToken field may be an empty string or missing when there are no additional results. The client must handle both cases.
400: The request is malformed.
HTTP Response Value
Header

Content-Type: application/json
Body 
{
  "errorCode": "string",
  "message": "string"
}
401: The request is unauthenticated. The bearer token is missing or incorrect.
HTTP Response Value
Header

Content-Type: application/json
Body 
{
  "errorCode": "string",
  "message": "string"
}
403: The request is forbidden from being fulfilled.
HTTP Response Value
Header

Content-Type: application/json
Body 
{
  "errorCode": "string",
  "message": "string"
}
404: The requested resource does not exist.
HTTP Response Value
Header

Content-Type: application/json
Body 
{
  "errorCode": "string",
  "message": "string"
}
500: The request is not handled correctly due to a server error.
HTTP Response Value
Header

Content-Type: application/json
Body 
{
  "errorCode": "string",
  "message": "string"
}

Example:

GET {prefix}/shares/vaccine_share/all-tables

{
  "items" : [
    {
      "share" : "vaccine_share",
      "schema" : "acme_vaccine_ingredient_data",
      "name" : "vaccine_ingredients",
      "shareId": "edacc4a7-6600-4fbb-85f3-a62a5ce6761f",
      "id": "2f9729e9-6fcf-4d34-96df-bf72b26dfbe9"
    },
    {
      "share": "vaccine_share",
      "schema": "acme_vaccine_patient_data",
      "name": "vaccine_patients",
      "shareId": "edacc4a7-6600-4fbb-85f3-a62a5ce6761f",
      "id": "74be6365-0fc8-4a2f-8720-0de125bb5832"
    }
  ],
  "nextPageToken": "..."
}

Query Table Version

This is the API for clients to get a table version without any other extra information. The server usually can implement this API effectively. If a client caches information about a shared table locally, it can store the table version and use this cheap API to quickly check whether their cache is stale and they should re-fetch the data.

Note: This method is migrating from HEAD to GET, and with a /version suffix. Please use the new API as we encourage that the HEAD API be deprecated by 07/01/2023.

HTTP Request Value
Method GET HEAD (deprecated)
HEADER

Authorization: Bearer {token}
URL

{prefix}/shares/{share}/schemas/{schema}/tables/{table}/version

{prefix}/shares/{share}/schemas/{schema}/tables/{table}
URL parameters

{share}: The share name to query. It's case-insensitive.
{schema}: The schema name to query. It's case-insensitive.
{table}: The table name to query. It's case-insensitive.
Query parameters

startingTimestamp (type: String, optional): The startingTimestamp of the query, a string in the Timestamp Format, the server needs to return the earliest table version at or after the provided timestamp, can be earlier than the timestamp of table version 0.

 N/A
200: The table version was successfully returned.
HTTP Response Value
Header

Delta-Table-Version: {version}

{version} is a long value which represents the current table version.
Body

Empty
400: The request is malformed.
HTTP Response Value
Header

Content-Type: application/json
Body 
{
  "errorCode": "string",
  "message": "string"
}
401: The request is unauthenticated. The bearer token is missing or incorrect.
HTTP Response Value
Header

Content-Type: application/json
Body 
{
  "errorCode": "string",
  "message": "string"
}
403: The request is forbidden from being fulfilled.
HTTP Response Value
Header

Content-Type: application/json
Body 
{
  "errorCode": "string",
  "message": "string"
}
404: The requested resource does not exist.
HTTP Response Value
Header

Content-Type: application/json
Body 
{
  "errorCode": "string",
  "message": "string"
}
500: The request is not handled correctly due to a server error.
HTTP Response Value
Header

Content-Type: application/json
Body 
{
  "errorCode": "string",
  "message": "string"
}

Example:

GET {prefix}/shares/vaccine_share/schemas/acme_vaccine_data/tables/vaccine_patients/version

HTTP/2 200 
delta-table-version: 123

Query Table Metadata

This is the API for clients to query the table schema and other metadata.

HTTP Request Value
Method GET
Header Authorization: Bearer {token}
URL {prefix}/shares/{share}/schemas/{schema}/tables/{table}/metadata
URL Parameters {share}: The share name to query. It's case-insensitive.
{schema}: The schema name to query. It's case-insensitive.
{table}: The table name to query. It's case-insensitive.
200: The table metadata was successfully returned.
HTTP Response Value
Headers

Content-Type: application/x-ndjson; charset=utf-8

Delta-Table-Version: {version}

{version} is a long value which represents the current table version.
Body

A sequence of JSON strings delimited by newline. Each line is a JSON object defined in API Response Format.

The response contains two lines:
400: The request is malformed.
HTTP Response Value
Header

Content-Type: application/json
Body 
{
  "errorCode": "string",
  "message": "string"
}
401: The request is unauthenticated. The bearer token is missing or incorrect.
HTTP Response Value
Header

Content-Type: application/json
Body 
{
  "errorCode": "string",
  "message": "string"
}
403: The request is forbidden from being fulfilled.
HTTP Response Value
Header

Content-Type: application/json
Body 
{
  "errorCode": "string",
  "message": "string"
}
404: The requested resource does not exist.
HTTP Response Value
Header

Content-Type: application/json
Body 
{
  "errorCode": "string",
  "message": "string"
}
500: The request is not handled correctly due to a server error.
HTTP Response Value
Header

Content-Type: application/json
Body 
{
  "errorCode": "string",
  "message": "string"
}

Example (See API Response Format for more details about the format):

GET {prefix}/shares/vaccine_share/schemas/acme_vaccine_data/tables/vaccine_patients/metadata

HTTP/2 200 
content-type: application/x-ndjson; charset=utf-8
delta-table-version: 123

{
  "protocol": {
    "minReaderVersion": 1
  }
}
{
  "metaData": {
    "id": "f8d5c169-3d01-4ca3-ad9e-7dc3355aedb2",
    "format": {
      "provider": "parquet"
    },
    "schemaString": "{\"type\":\"struct\",\"fields\":[{\"name\":\"eventTime\",\"type\":\"timestamp\",\"nullable\":true,\"metadata\":{}},{\"name\":\"date\",\"type\":\"date\",\"nullable\":true,\"metadata\":{}}]}",
    "partitionColumns": [
      "date"
    ]
  }
}

Read Data from a Table

This is the API for clients to read data from a table.

HTTP Request Value
Method `POST`
Headers

Authorization: Bearer {token}

Content-Type: application/json; charset=utf-8
URL

{prefix}/shares/{share}/schemas/{schema}/tables/{table}/query
URL Parameters

{share}: The share name to query. It's case-insensitive.

{schema}: The schema name to query. It's case-insensitive.

{table}: The table name to query. It's case-insensitive.
Body (an example) 
{
  "predicateHints": [
    "string"
  ],
  "limitHint": 0,
  "version": 0,
  "jsonPredicateHints": "string"
}

See below for more details.
200: The tables were successfully returned.
HTTP Response Value
Headers

Content-Type: application/x-ndjson; charset=utf-8

Delta-Table-Version: {version}

{version} is a long value:

  • when no time travel parameters are provided in the request, it represents the current table version.
  • otherwise, it represents the starting version of files returned in the response.
Body

A sequence of JSON strings delimited by newline. Each line is a JSON object defined in API Response Format.

The response contains multiple lines:
400: The request is malformed.
HTTP Response Value
Header

Content-Type: application/json
Body 
{
  "errorCode": "string",
  "message": "string"
}
401: The request is unauthenticated. The bearer token is missing or incorrect.
HTTP Response Value
Header

Content-Type: application/json
Body 
{
  "errorCode": "string",
  "message": "string"
}
403: The request is forbidden from being fulfilled.
HTTP Response Value
Header

Content-Type: application/json
Body 
{
  "errorCode": "string",
  "message": "string"
}
404: The requested resource does not exist.
HTTP Response Value
Header

Content-Type: application/json
Body 
{
  "errorCode": "string",
  "message": "string"
}
500: The request is not handled correctly due to a server error.
HTTP Response Value
Header

Content-Type: application/json
Body 
{
  "errorCode": "string",
  "message": "string"
}

Request Body

The request body should be a JSON string containing the following optional fields:

  • predicateHints (type: String, optional): a list of SQL boolean expressions using a restricted subset of SQL, in a JSON array.

    • When it’s present, the server will use the provided predicates as a hint to apply the SQL predicates on the returned files.
      • Filtering files based on the SQL predicates is BEST EFFORT. The server may return files that don’t satisfy the predicates.
      • If the server fails to parse one of the SQL predicates, or fails to evaluate it, the server may skip it.
      • Predicate expressions are conjunctive (AND-ed together).
    • When it’s absent, the server will return all of files in the table.
    • This will be deprecated once all the client and server implementation move to using jsonPredicateHints below.

  • jsonPredicateHints (type: String, optional): query predicates on partition columns specified using a structured JSON format.

    • When it’s present, the server will try to use the predicates to filter table's files, which could boost query performance.
      • As with predicateHints, this filtering is BEST EFFORT. The server may return files that don’t satisfy the predicates.
      • If the server encounters any errors during predicate processing (for example, invalid syntax or non existing columns), it will skip filtering and return all the files.
    • When it’s absent, the server will return all the files in the table.

  • limitHint (type: Int32, optional): an optional limit number. It’s a hint from the client to tell the server how many rows in the table the client plans to read. The server can use this hint to return only some files by using the file stats. For example, when running SELECT * FROM table LIMIT 1000, the client can set limitHint to 1000.

    • Applying limitHint is BEST EFFORT. The server may return files containing more rows than the client requests.

  • version (type: Long, optional): an optional version number. If set, will return files as of the specified version of the table. This is only supported on tables with history sharing enabled.

  • timestamp (type: String, optional): an optional timestamp string in the Timestamp Format,. If set, will return files as of the table version corresponding to the specified timestamp. This is only supported on tables with history sharing enabled.

  • startingVersion (type: Long, optional): an optional version number. If set, will return all data change files since startingVersion, inclusive, including historical metadata if seen in the delta log.

  • endingVersion (type: Long, optional): an optional version number, only used if startingVersion is set. If set, the server can use it as a hint to avoid returning data change files after endingVersion. This is not enforcement. Hence, when sending the endingVersion parameter, the client should still handle the case that it may receive files after endingVersion.

    • The combination of statingVersion and endingVersion can be used as query window for delta sharing streaming rpcs.

When predicateHints and limitHint are both present, the server should apply predicateHints first then limitHint. As these two parameters are hints rather than enforcement, the client must always apply predicateHints and limitHint on the response returned by the server if it wishes to filter and limit the returned data. An empty JSON object ({}) should be provided when these two parameters are missing.

Example (See API Response Format for more details about the format):

POST {prefix}/shares/vaccine_share/schemas/acme_vaccine_data/tables/vaccine_patients/query

{
  "predicateHints": [
    "date >= '2021-01-01'",
    "date <= '2021-01-31'"
  ],
  "limitHint": 1000,
  "version": 123
}
HTTP/2 200 
content-type: application/x-ndjson; charset=utf-8
delta-table-version: 123

{
  "protocol": {
    "minReaderVersion": 1
  }
}
{
  "metaData": {
    "id": "f8d5c169-3d01-4ca3-ad9e-7dc3355aedb2",
    "format": {
      "provider": "parquet"
    },
    "schemaString": "{\"type\":\"struct\",\"fields\":[{\"name\":\"eventTime\",\"type\":\"timestamp\",\"nullable\":true,\"metadata\":{}},{\"name\":\"date\",\"type\":\"date\",\"nullable\":true,\"metadata\":{}}]}",
    "partitionColumns": [
      "date"
    ]
  }
}
{
  "file": {
    "url": "https://<s3-bucket-name>.s3.us-west-2.amazonaws.com/delta-exchange-test/table2/date%3D2021-04-28/part-00000-8b0086f2-7b27-4935-ac5a-8ed6215a6640.c000.snappy.parquet?X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Date=20210501T010516Z&X-Amz-SignedHeaders=host&X-Amz-Expires=900&X-Amz-Credential=AKIAISZRDL4Q4Q7AIONA%2F20210501%2Fus-west-2%2Fs3%2Faws4_request&X-Amz-Signature=97b6762cfd8e4d7e94b9d707eff3faf266974f6e7030095c1d4a66350cfd892e",
    "id": "8b0086f2-7b27-4935-ac5a-8ed6215a6640",
    "partitionValues": {
      "date": "2021-04-28"
    },
    "size":573,
    "stats": "{\"numRecords\":1,\"minValues\":{\"eventTime\":\"2021-04-28T23:33:57.955Z\"},\"maxValues\":{\"eventTime\":\"2021-04-28T23:33:57.955Z\"},\"nullCount\":{\"eventTime\":0}}"
  }
}
{
  "file": {
    "url": "https://<s3-bucket-name>.s3.us-west-2.amazonaws.com/delta-exchange-test/table2/date%3D2021-04-28/part-00000-591723a8-6a27-4240-a90e-57426f4736d2.c000.snappy.parquet?X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Date=20210501T010516Z&X-Amz-SignedHeaders=host&X-Amz-Expires=899&X-Amz-Credential=AKIAISZRDL4Q4Q7AIONA%2F20210501%2Fus-west-2%2Fs3%2Faws4_request&X-Amz-Signature=0f7acecba5df7652457164533a58004936586186c56425d9d53c52db574f6b62",
    "id": "591723a8-6a27-4240-a90e-57426f4736d2",
    "partitionValues": {
      "date": "2021-04-28"
    },
    "size": 573,
    "stats": "{\"numRecords\":1,\"minValues\":{\"eventTime\":\"2021-04-28T23:33:48.719Z\"},\"maxValues\":{\"eventTime\":\"2021-04-28T23:33:48.719Z\"},\"nullCount\":{\"eventTime\":0}}"
  }
}

Read Change Data Feed from a Table

This is the API for clients to read change data feed from a table.

The API supports a start parameter and and an end parameter. The start/end parameter can either be a version or a timestamp. The start parameter must be provided. If the end parameter is not provided, the API will use the latest table version for it. The parameter range is inclusive in the query.

You can specify a version as a Long or a timestamp as a string in the Timestamp Format.

The change data feed represents row-level changes between versions of a Delta table. It records change data for UPDATE, DELETE, and MERGE operations. If you leverage the connectors provided by this library to read change data feed, it results in three metadata columns that identify the type of change event, in addition to the data columns:

  • _change_type (type: String): There are four values: insert, update_preimage, update_postimage, delete. preimage is the value before the udpate, postimage is the value after the update.
  • _commit_version (type: Long): The table version containing the change.
  • _commit_timestamp (type: Long): The unix timestamp associated when the commit of the change was created, in milliseconds.

HTTP Request Value
Method

GET
Header

Authorization: Bearer {token}
URL

{prefix}/shares/{share}/schemas/{schema}/tables/{table}/changes
URL Parameters

{share}: The share name to query. It's case-insensitive.
{schema}: The schema name to query. It's case-insensitive.
{table}: The table name to query. It's case-insensitive.
Query Parameters

startingVersion (type: Long, optional): The starting version of the query, inclusive.
startingTimestamp (type: String, optional): The starting timestamp of the query, a string in the Timestamp Format, which will be converted to a version created greater or equal to this timestamp.
endingVersion (type: Long, optional): The ending version of the query, inclusive.
endingTimestamp (type: String, optional): The ending timestamp of the query, a string in the Timestamp Format, which will be converted to a version created earlier than or at the timestamp.
includeHistoricalMetadata (type: Boolean, optional): If set to true, return the historical metadata if seen in the delta log. This is for the streaming client to check if the table schema is still read compatible.
200: The change data feed was successfully returned.
HTTP Response Value
Headers

Content-Type: application/x-ndjson; charset=utf-8

Delta-Table-Version: {version}

{version} is a long value which represents the starting version of files in the response.
Body

A sequence of JSON strings delimited by newline. Each line is a JSON object defined in API Response Format.

The response contains multiple lines:
400: The request is malformed.
HTTP Response Value
Header

Content-Type: application/json
Body 
{
  "errorCode": "string",
  "message": "string"
}
401: The request is unauthenticated. The bearer token is missing or incorrect.
HTTP Response Value
Header

Content-Type: application/json
Body 
{
  "errorCode": "string",
  "message": "string"
}
403: The request is forbidden from being fulfilled.
HTTP Response Value
Header

Content-Type: application/json
Body 
{
  "errorCode": "string",
  "message": "string"
}
404: The requested resource does not exist.
HTTP Response Value
Header

Content-Type: application/json
Body 
{
  "errorCode": "string",
  "message": "string"
}
500: The request is not handled correctly due to a server error.
HTTP Response Value
Header

Content-Type: application/json
Body 
{
  "errorCode": "string",
  "message": "string"
}

Example (See API Response Format for more details about the format):

GET {prefix}/shares/vaccine_share/schemas/acme_vaccine_data/tables/vaccine_patients/changes?startingVersion=0&endingVersion=2

HTTP/2 200 
content-type: application/x-ndjson; charset=utf-8

{
  "protocol": {
    "minReaderVersion": 1
  }
}
{
  "metaData": {
    "id": "f8d5c169-3d01-4ca3-ad9e-7dc3355aedb2",
    "format": {
      "provider": "parquet"
    },
    "schemaString": "{\"type\":\"struct\",\"fields\":[{\"name\":\"eventTime\",\"type\":\"timestamp\",\"nullable\":true,\"metadata\":{}},{\"name\":\"date\",\"type\":\"date\",\"nullable\":true,\"metadata\":{}}]}",
    "partitionColumns": [
      "date"
    ],
    "configuration": {
      "enableChangeDataFeed": "true"
    }
  }
}
{
  "add": {
    "url": "https://<s3-bucket-name>.s3.us-west-2.amazonaws.com/delta-exchange-test/table_cdf/date%3D2021-04-28/part-00000-8b0086f2-7b27-4935-ac5a-8ed6215a6640.c000.snappy.parquet?X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Date=20210501T010516Z&X-Amz-SignedHeaders=host&X-Amz-Expires=900&X-Amz-Credential=AKIAISZRDL4Q4Q7AIONA%2F20210501%2Fus-west-2%2Fs3%2Faws4_request&X-Amz-Signature=97b6762cfd8e4d7e94b9d707eff3faf266974f6e7030095c1d4a66350cfd892e",
    "id": "8b0086f2-7b27-4935-ac5a-8ed6215a6640",
    "partitionValues": {
      "date": "2021-04-28"
    },
    "size":573,
    "stats": "{\"numRecords\":1,\"minValues\":{\"eventTime\":\"2021-04-28T23:33:57.955Z\"},\"maxValues\":{\"eventTime\":\"2021-04-28T23:33:57.955Z\"},\"nullCount\":{\"eventTime\":0}}",
    "timestamp": 1652140000000,
    "version": 0
  }
}
{
  "cdf": {
    "url": "https://<s3-bucket-name>.s3.us-west-2.amazonaws.com/delta-exchange-test/table_cdf/_change_data/date%3D2021-04-28/part-00000-591723a8-6a27-4240-a90e-57426f4736d2.c000.snappy.parquet?X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Date=20210501T010516Z&X-Amz-SignedHeaders=host&X-Amz-Expires=899&X-Amz-Credential=AKIAISZRDL4Q4Q7AIONA%2F20210501%2Fus-west-2%2Fs3%2Faws4_request&X-Amz-Signature=0f7acecba5df7652457164533a58004936586186c56425d9d53c52db574f6b62",
    "id": "591723a8-6a27-4240-a90e-57426f4736d2",
    "partitionValues": {
      "date": "2021-04-28"
    },
    "size": 689,
    "timestamp": 1652141000000,
    "version": 1
  }
}
{
  "remove": {
    "url": "https://<s3-bucket-name>.s3.us-west-2.amazonaws.com/delta-exchange-test/table_cdf/date%3D2021-04-28/part-00000-8b0086f2-7b27-4935-ac5a-8ed6215a6640.c000.snappy.parquet?X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Date=20210501T010516Z&X-Amz-SignedHeaders=host&X-Amz-Expires=900&X-Amz-Credential=AKIAISZRDL4Q4Q7AIONA%2F20210501%2Fus-west-2%2Fs3%2Faws4_request&X-Amz-Signature=97b6762cfd8e4d7e94b9d707eff3faf266974f6e7030095c1d4a66350cfd892e",
    "id": "8b0086f2-7b27-4935-ac5a-8ed6215a6640",
    "partitionValues": {
      "date": "2021-04-28"
    },
    "size": 573,
    "timestamp": 1652142000000,
    "version": 2
  }
}

Timestamp Format

Accepted timestamp format by a delta sharing server: yyyy-[m]m-[d]d hh:mm:ss[.f...]. The server will use its local time zone to parse the provided timestamp.

API Response Format

This section discusses the API Response Format returned by the server.

JSON Wrapper Object In Each Line

The JSON object in each line is a wrapper object that may contain the following fields:

Field Name Data Type Description Optional/Required
protocol The Protocol JSON object. Defines the versioning information about the API Response Format. Optional
metaData The Metadata JSON object. The table metadata including schema, partitionColumns, etc. Optional
file The File JSON object. An individual data file in the table. Optional

It must contain only ONE of the above fields.

Protocol

Protocol versioning will allow servers to exclude older clients that are missing features required to correctly interpret their response if the Delta Sharing Protocol evolves in the future. The protocol version will be increased whenever non-forward-compatible changes are made to the protocol. When a client is running an unsupported protocol version, it should show an error message instructing the user to upgrade to a newer version of their client.

Since only breaking changes must be accompanied by an increase in the protocol version recorded in a table, clients can assume that any unrecognized fields in a response that supports their reader version are never required in order to correctly interpret the response.

Field Name Data Type Description Optional/Required
minReaderVersion Int32 The minimum version of the protocol that a client must implement in order to correctly read a Delta Lake table. Currently it’s always 1. It will be changed in future when we introduce non-forward-compatible changes that require clients to implement. Required

Example (for illustration purposes; each JSON object must be a single line in the response):

{
  "protocol": {
    "minReaderVersion": 1
  }
}

Metadata

Field Name Data Type Description Optional/Required
id String Unique identifier for this table Required
name String User-provided identifier for this table Optional
description String User-provided description for this table Optional
format Format Object Specification of the encoding for the files stored in the table. Required
schemaString String Schema of the table. This is a serialized JSON string which can be deserialized to a Schema Object. Required
partitionColumns Array An array containing the names of columns by which the data should be partitioned. When a table doesn’t have partition columns, this will be an empty array. Required
configuration Map[String, String] A map containing configuration options for the table
version Long The table version the metadata corresponds to, returned when querying table data with a version or timestamp parameter, or cdf query with includeHistoricalMetadata set to true. Optional
size Long The size of the table in bytes, will be returned if available in the delta log. Optional
numFiles Long The number of files in the table, will be returned if available in the delta log. Optional

Example (for illustration purposes; each JSON object must be a single line in the response):

{
  "metaData": {
    "partitionColumns": [
      "date"
    ],
    "format": {
      "provider": "parquet"
    },
    "schemaString": "{\"type\":\"struct\",\"fields\":[{\"name\":\"eventTime\",\"type\":\"timestamp\",\"nullable\":true,\"metadata\":{}},{\"name\":\"date\",\"type\":\"date\",\"nullable\":true,\"metadata\":{}}]}",
    "id": "f8d5c169-3d01-4ca3-ad9e-7dc3355aedb2",
    "configuration": {
      "enableChangeDataFeed": "true"
    },
    "size": 123456,
    "numFiles": 5
  }
}

File

Field Name Data Type Description Optional/Required
url String An https url that a client can use to read the file directly. The same file in different responses may have different urls. Required
id String A unique string for the file in a table. The same file is guaranteed to have the same id across multiple requests. A client may cache the file content and use this id as a key to decide whether to use the cached file content. Required
partitionValues Map<String, String> A map from partition column to value for this file. See Partition Value Serialization for how to parse the partition values. When the table doesn’t have partition columns, this will be an empty map. Required
size Long The size of this file in bytes. Required
stats String Contains statistics (e.g., count, min/max values for columns) about the data in this file. This field may be missing. A file may or may not have stats. This is a serialized JSON string which can be deserialized to a Statistics Struct. A client can decide whether to use stats or drop it. Optional
version Long The table version of the file, returned when querying a table data with a version or timestamp parameter. Optional
timestamp Long The unix timestamp corresponding to the table version of the file, in milliseconds, returned when querying a table data with a version or timestamp parameter. Optional
expirationTimestamp Long The unix timestamp corresponding to the expiration of the url, in milliseconds, returned when the server supports the feature. Optional

Example (for illustration purposes; each JSON object must be a single line in the response):

{
  "file": {
    "url": "https://<s3-bucket-name>.s3.us-west-2.amazonaws.com/delta-exchange-test/table2/date%3D2021-04-28/part-00000-591723a8-6a27-4240-a90e-57426f4736d2.c000.snappy.parquet?X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Date=20210501T010655Z&X-Amz-SignedHeaders=host&X-Amz-Expires=900&X-Amz-Credential=AKIAISZRDL4Q4Q7AIONA%2F20210501%2Fus-west-2%2Fs3%2Faws4_request&X-Amz-Signature=dd5d3ba1a179dc7e239d257feed046dccc95000d1aa0479ea6ff36d10d90ec94",
    "id": "591723a8-6a27-4240-a90e-57426f4736d2",
    "size": 573,
    "partitionValues": {
      "date": "2021-04-28"
    },
    "stats": "{\"numRecords\":1,\"minValues\":{\"eventTime\":\"2021-04-28T23:33:48.719Z\"},\"maxValues\":{\"eventTime\":\"2021-04-28T23:33:48.719Z\"},\"nullCount\":{\"eventTime\":0}}",
    "expirationTimestamp": 1652140800000
  }
}

Data Change Files

Add File

Field Name Data Type Description Optional/Required
url String An https url that a client can use to read the file directly. The same file in different responses may have different urls. Required
id String A unique string for the file in a table. The same file is guaranteed to have the same id across multiple requests. A client may cache the file content and use this id as a key to decide whether to use the cached file content. Required
partitionValues Map<String, String> A map from partition column to value for this file. See Partition Value Serialization for how to parse the partition values. When the table doesn’t have partition columns, this will be an empty map. Required
size Long The size of this file in bytes. Required
timestamp Long The timestamp of the file in milliseconds from epoch. Required
version Int32 The table version of this file. Required
stats String Contains statistics (e.g., count, min/max values for columns) about the data in this file. This field may be missing. A file may or may not have stats. This is a serialized JSON string which can be deserialized to a Statistics Struct. A client can decide whether to use stats or drop it. Optional
expirationTimestamp Long The unix timestamp corresponding to the expiration of the url, in milliseconds, returned when the server supports the feature. Optional

Example (for illustration purposes; each JSON object must be a single line in the response):

{
  "add": {
    "url": "https://<s3-bucket-name>.s3.us-west-2.amazonaws.com/delta-exchange-test/table_cdf/date%3D2021-04-28/part-00000-591723a8-6a27-4240-a90e-57426f4736d2.c000.snappy.parquet?X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Date=20210501T010655Z&X-Amz-SignedHeaders=host&X-Amz-Expires=900&X-Amz-Credential=AKIAISZRDL4Q4Q7AIONA%2F20210501%2Fus-west-2%2Fs3%2Faws4_request&X-Amz-Signature=dd5d3ba1a179dc7e239d257feed046dccc95000d1aa0479ea6ff36d10d90ec94",
    "id": "591723a8-6a27-4240-a90e-57426f4736d2",
    "size": 573,
    "partitionValues": {
      "date": "2021-04-28"
    },
    "timestamp": 1652140800000,
    "version": 1,
    "stats": "{\"numRecords\":1,\"minValues\":{\"eventTime\":\"2021-04-28T23:33:48.719Z\"},\"maxValues\":{\"eventTime\":\"2021-04-28T23:33:48.719Z\"},\"nullCount\":{\"eventTime\":0}}",
    "expirationTimestamp": 1652144400000
  }
}

CDF File

Field Name Data Type Description Optional/Required
url String An https url that a client can use to read the file directly. The same file in different responses may have different urls. Required
id String A unique string for the file in a table. The same file is guaranteed to have the same id across multiple requests. A client may cache the file content and use this id as a key to decide whether to use the cached file content. Required
partitionValues Map<String, String> A map from partition column to value for this file. See Partition Value Serialization for how to parse the partition values. When the table doesn’t have partition columns, this will be an empty map. Required
size Long The size of this file in bytes. Required
timestamp Long The timestamp of the file in milliseconds from epoch. Required
version Int32 The table version of this file. Required
expirationTimestamp Long The unix timestamp corresponding to the expiration of the url, in milliseconds, returned when the server supports the feature. Optional

Example (for illustration purposes; each JSON object must be a single line in the response):

{
  "cdf": {
    "url": "https://<s3-bucket-name>.s3.us-west-2.amazonaws.com/delta-exchange-test/table_cdf/_change_data/date%3D2021-04-28/part-00000-591723a8-6a27-4240-a90e-57426f4736d2.c000.snappy.parquet?X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Date=20210501T010655Z&X-Amz-SignedHeaders=host&X-Amz-Expires=900&X-Amz-Credential=AKIAISZRDL4Q4Q7AIONA%2F20210501%2Fus-west-2%2Fs3%2Faws4_request&X-Amz-Signature=dd5d3ba1a179dc7e239d257feed046dccc95000d1aa0479ea6ff36d10d90ec94",
    "id": "591723a8-6a27-4240-a90e-57426f4736d2",
    "size": 573,
    "partitionValues": {
      "date": "2021-04-28"
    },
    "timestamp": 1652140800000,
    "version": 1,
    "expirationTimestamp": 1652144400000
  }
}

Remove File

Field Name Data Type Description Optional/Required
url String An https url that a client can use to read the file directly. The same file in different responses may have different urls. Required
id String A unique string for the file in a table. The same file is guaranteed to have the same id across multiple requests. A client may cache the file content and use this id as a key to decide whether to use the cached file content. Required
partitionValues Map<String, String> A map from partition column to value for this file. See Partition Value Serialization for how to parse the partition values. When the table doesn’t have partition columns, this will be an empty map. Required
size Long The size of this file in bytes. Required
timestamp Long The timestamp of the file in milliseconds from epoch. Required
version Int32 The table version of this file. Required
expirationTimestamp Long The unix timestamp corresponding to the expiration of the url, in milliseconds, returned when the server supports the feature. Optional

Example (for illustration purposes; each JSON object must be a single line in the response):

{
  "remove": {
    "url": "https://<s3-bucket-name>.s3.us-west-2.amazonaws.com/delta-exchange-test/table_cdf/date%3D2021-04-28/part-00000-591723a8-6a27-4240-a90e-57426f4736d2.c000.snappy.parquet?X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Date=20210501T010655Z&X-Amz-SignedHeaders=host&X-Amz-Expires=900&X-Amz-Credential=AKIAISZRDL4Q4Q7AIONA%2F20210501%2Fus-west-2%2Fs3%2Faws4_request&X-Amz-Signature=dd5d3ba1a179dc7e239d257feed046dccc95000d1aa0479ea6ff36d10d90ec94",
    "id": "591723a8-6a27-4240-a90e-57426f4736d2",
    "size": 573,
    "partitionValues": {
      "date": "2021-04-28"
    },
    "timestamp": 1652140800000,
    "version": 1,
    "expirationTimestamp": 1652144400000
  }
}

Format

Field Name Data Type Description Optional/Required
provider String Name of the encoding for data files in this table. Currently the only valid value is parquet. This is to enable possible support for other formats in the future. Required

Schema Object

We use a subset of Spark SQL's JSON Schema representation to represent the schema of a table. A reference implementation can be found in the Catalyst package of the Apache Spark repository.

Struct Type

A struct is used to represent both the top-level schema of the table as well as struct columns that contain nested columns. A struct is encoded as a JSON object with the following fields:

Field Name Description
type Always the string struct
fields An array of fields

Struct Field

A struct field represents a top-level or nested column.

Field Name Description
name Name of this (possibly nested) column
type String containing the name of a primitive type, a struct definition, an array definition or a map definition
nullable Boolean denoting whether this field can be null
metadata A JSON map containing information about this column. For example, the comment key means its value is the column comment.

Primitive Types

Field Name Description
string UTF-8 encoded string of characters
long 8-byte signed integer. Range: -9223372036854775808 to 9223372036854775807
integer 4-byte signed integer. Range: -2147483648 to 2147483647
short 2-byte signed integer numbers. Range: -32768 to 32767
byte 1-byte signed integer number. Range: -128 to 127
float 4-byte single-precision floating-point numbers
double 8-byte double-precision floating-point numbers
boolean true or false
binary A sequence of binary data
date A calendar date, represented as a year-month-day triple without a timezone
timestamp Microsecond precision timestamp without a timezone
decimal signed decimal number with fixed precision (maximum number of digits) and scale (number of digits on right side of dot). The precision and scale can be up to 38.

Array Type

An array stores a variable length collection of items of some type.

Field Name Description
type Always the string array
elementType The type of element stored in this array represented as a string containing the name of a primitive type, a struct definition, an array definition or a map definition
containsNull Boolean denoting whether this array can contain one or more null values

Map Type

A map stores an arbitrary length collection of key-value pairs with a single keyType and a single valueType.

Field Name Description
type Always the string map
keyType The type of element used for the key of this map, represented as a string containing the name of a primitive type, a struct definition, an array definition or a map definition
valueType The type of element used for the key of this map, represented as a string containing the name of a primitive type, a struct definition, an array definition or a map definition
valueContainsNull Indicates if map values have null values.

Example

Example Table Schema:

|-- a: integer (nullable = false)
|-- b: struct (nullable = true)
|    |-- d: integer (nullable = false)
|-- c: array (nullable = true)
|    |-- element: integer (containsNull = false)
|-- e: array (nullable = true)
|    |-- element: struct (containsNull = true)
|    |    |-- d: integer (nullable = false)
|-- f: map (nullable = true)
|    |-- key: string
|    |-- value: string (valueContainsNull = true)

JSON Encoded Table Schema:

{
  "type": "struct",
  "fields": [
    {
      "name": "a",
      "type": "integer",
      "nullable": false,
      "metadata": {
        "comment": "this is a comment"
      }
    },
    {
      "name": "b",
      "type": {
        "type": "struct",
        "fields": [
          {
            "name": "d",
            "type": "integer",
            "nullable": false,
            "metadata": {}
          }
        ]
      },
      "nullable": true,
      "metadata": {}
    },
    {
      "name": "c",
      "type": {
        "type": "array",
        "elementType": "integer",
        "containsNull": false
      },
      "nullable": true,
      "metadata": {}
    },
    {
      "name": "e",
      "type": {
        "type": "array",
        "elementType": {
          "type": "struct",
          "fields": [
            {
              "name": "d",
              "type": "integer",
              "nullable": false,
              "metadata": {}
            }
          ]
        },
        "containsNull": true
      },
      "nullable": true,
      "metadata": {}
    },
    {
      "name": "f",
      "type": {
        "type": "map",
        "keyType": "string",
        "valueType": "string",
        "valueContainsNull": true
      },
      "nullable": true,
      "metadata": {}
    }
  ]
}

Partition Value Serialization

Partition values are stored as strings, using the following formats. An empty string for any type translates to a null partition value.

Type Serialization Format
string No translation required
numeric types The string representation of the number
date Encoded as {year}-{month}-{day}. For example, 1970-01-01
timestamp Encoded as {year}-{month}-{day} {hour}:{minute}:{second}. For example: 1970-01-01 00:00:00
boolean Encoded as the string true or false

Per-file Statistics

A File JSON object can optionally contain statistics about the data in the file being added to the table. These statistics can be used for eliminating files based on query predicates or as inputs to query optimization.

Global statistics record information about the entire file. The following global statistic is currently supported:

Name Description
numRecords The number of records in this file.

Per-column statistics record information for each column in the file and they are encoded, mirroring the schema of the actual data. For example, given the following data schema:

|-- a: struct
|    |-- b: struct
|    |    |-- c: long

Statistics could be stored with the following schema:

|-- stats: struct
|    |-- numRecords: long
|    |-- minValues: struct
|    |    |-- a: struct
|    |    |    |-- b: struct
|    |    |    |    |-- c: long
|    |-- maxValues: struct
|    |    |-- a: struct
|    |    |    |-- b: struct
|    |    |    |    |-- c: long

Example 1:

Column Type:

|-- a: long

JSON stats:

{
   "numRecords": 1,
   "maxValues": {
      "a": 123
   },
   "minValues": {
      "a": 123
   },
   "nullCount": {
      "a": 0
   }
}

Example 2:

Column Type:

|-- a: struct
|    |-- b: struct
|    |    |-- c: long

JSON stats:

{
   "minValues": {
      "a": {
         "b": {
            "c": 123
         }
      }
   },
   "maxValues": {
      "a": {
         "b": {
            "c": 123
         }
      }
   },
   "nullCount": {
      "a": {
         "b": {
            "c": 0
         }
      }
   },
   "numRecords": 1
}

The following per-column statistics are currently supported:

Name Description
nullCount The number of null values for this column
minValues A value smaller than all values present in the file for this column
maxValues A value larger than all values present in the file for this column

SQL Expressions for Filtering

The client may send a sequence of predicates to the server as a hint to request fewer files when it only wishes to query a subset of the data (e.g., data where the country field is US). The server may try its best to filter files based on the predicates. This is BEST EFFORT, so the server may return files that don’t satisfy the predicates. For example, if the server fails to parse a SQL expression, the server can skip it. Hence, the client should always apply predicates to filter the data returned by the server.

At the beginning, the server will support the following simple comparison expressions between a column in the table and a constant value.

Expression Example
= col = 123
> col > 'foo'
< 'foo' < col
>= col >= 123
<= 123 <= col
<> col <> 'foo'
IS NULL col IS NULL
IS NOT NULL col IS NOT NULL

More expression support will be added incrementally in future.

JSON predicates for Filtering

The client may send filtering predicates on partition columns using a structured JSON format. This is similar to SQL expressions for Filtering, but uses a simpler JSON tree structure. The partition column predicates are simple to express, and do not need the full expressive power of SQL. Using a structured JSON format to represent these predicates enables easier and safer support for file filtering capabilities in Delta Sharing server implementations.

The server may try its best to filter files based on the predicates in a BEST EFFORT mode. The server may return all the files if validations fail. So clients should apply these predicates to the filter the data returned by the server.

We will deprecate the legacy predicateHints once all the delta sharing client and servers have moved to the json predicate based file filtering.

The JSON format:

Field Name Descrption
op The name of the operation. See the section on supported ops for details.
children The child operations for the op. This allows us to represent a predicate tree. Leaf ops do not have any children. Unary ops such as not have only one child. Binary ops such as equal have two children. Nary ops such as and can have multiple children.
name Specifies the name of a column. This is only applicable to column ops.
value Specifies the value of a literal. This is only applicable to literal ops.
valueType Specifies the value type of a column or a literal op. This is only applicate to column and literal ops.

The supported Ops:

Op Op Type Description
column Leaf Represents a column. A column op has two fields: name and valueType. The column's value will be cast to the specified valueType during comparisons.
literal Leaf Represents a literal or fixed value. A literal op has two fields: value and valueType. The literal's value will be cast to the specified valueType during comparisons.
isNull Unary Represents a null check on a column op. This op should have only one child, the column op.
equal Binary Represents an equality ("=") check. This op should have two children, and both should be leaf ops.
lessThan Binary Represents a less than ("<") check. This op should have two children, and both should be leaf ops.
lessThanOrEqual Binary Represents a less than or equal ("<=") check. This op should have two children, and both should be leaf ops.
greaterThan Binary Represents a greater than (">") check. This op should have two children, and both should be leaf ops.
greaterThanOrEqual Binary Represents a greater than (">=") check. This op should have two children, and both should be leaf ops.
and Nary Represents a logical and operation amongst its children. This op should have at least two children.
or Nary Represents a logical or operation amongst its children. This op should have at least two children.
not Unary Represents a logical not check. This op should have once child.

The supported value types:

ValueType Description
"bool" Represents an Boolean type.
"int" Represents an Integer type.
"long" Represents a Long type.
"string" Represents a String type.
"date" Represents a Date type in "yyyy-mm-dd" format.

Examples

  1. Equal op.
{
  "op": "equal",
  "children": [
    {"op": "column", "name":"hireDate", "valueType":"date"},
    {"op":"literal","value":"2021-04-29","valueType":"date"}
  ]
}
  1. And op.
{
  "op":"and",
  "children":[
    {
      "op":"equal",
      "children":[
        {"op":"column","name":"hireDate","valueType":"date"},
        {"op":"literal","value":"2021-04-29","valueType":"date"}
      ]
    },
    {
      "op":"lessThan","children":[
        {"op":"column","name":"id","valueType":"int"},
        {"op":"literal","value":"25","valueType":"int"}
      ]
    }
  ]
}
  1. Not null check.
{
  "op": "not",
  "children": [
    {
      "op": "isNull",
      "children":[
        {"op":"column","name":"id","valueType":"int"},
      ]
    }
  ]
}

Profile File Format

A profile file is a JSON file that contains the information for a recipient to access shared data on a Delta Sharing server. There are a few fields in this file as listed below.

Field Name Descrption
shareCredentialsVersion The file format version of the profile file. This version will be increased whenever non-forward-compatible changes are made to the profile format. When a client is running an unsupported profile file format version, it should show an error message instructing the user to upgrade to a newer version of their client.
endpoint The url of the sharing server.
bearerToken The bearer token to access the server.
expirationTime The expiration time of the bearer token in ISO 8601 format. This field is optional and if it is not provided, the bearer token can be seen as never expire.

Example:

{
  "shareCredentialsVersion": 1,
  "endpoint": "https://sharing.delta.io/delta-sharing/",
  "bearerToken": "<token>",
  "expirationTime": "2021-11-12T00:12:29.0Z"
}