HDFS Connection Details¶

Introduction¶

Connector Version

This documentation is based on version 23.0.8895 of the connector.

Get Started¶

HDFS Version Support

The connector leverages the HDFS API to enable bidirectional access to HDFS.

Establish a Connection¶

Connect to HDFS¶

In order to connect, set the following connection properties:

• Host: Set this value to the host of your HDFS installation.
• Port: Set this value to the port of your HDFS installation. Default port: 50070
• UseSSL: (Optional) Set this value to 'True', to negotiate TLS/SSL connections to the HDFS server. Default: 'False'.

Authenticate to HDFS¶

There are two authentication methods available for connecting to the HDFS data source, Anonymous Authentication and Negotiate (Kerberos) Authentication.

Anonymous Authentication¶

In some situations, HDFS may be connected to without any authentication connection properties. To do so, set the AuthScheme to None (default).

Kerberos¶

When authentication credentials are required, you can use Kerberos. See Using Kerberos for details on how to authenticate with Kerberos.

Fine-Tuning Data Access¶

Fine Tuning Data Access¶

You can use the following properties to gain more control over the data returned from HDFS:

• DirectoryRetrievalDepth: How many subfolders to be recursively scanned before stopping.
  -1 specifies that all subfolders are scanned. 0 specifies that only the current folder will be scanned for items.
• Path: Limit the subfolders recursively scanned.

Use Kerberos¶

Kerberos¶

To authenticate to HDFS with Kerberos, set AuthScheme to NEGOTIATE.

Authenticating to HDFS via Kerberos requires you to define authentication properties and to choose how Kerberos should retrieve authentication tickets.

Retrieve Kerberos Tickets¶

Kerberos tickets are used to authenticate the requester's identity. The use of tickets instead of formal logins/passwords eliminates the need to store passwords locally or send them over a network. Users are reauthenticated (tickets are refreshed) whenever they log

in at their local computer or enter kinit USER at the command prompt.

The connector provides three ways to retrieve the required Kerberos ticket, depending on whether or not the KRB5CCNAME and/or KerberosKeytabFile variables exist in your environment.

MIT Kerberos Credential Cache File

This option enables you to use the MIT Kerberos Ticket Manager or kinit command to get tickets. With this option there is no need to set the User or Password connection properties.

This option requires that KRB5CCNAME has been created in your system.

To enable ticket retrieval via MIT Cerberos Credential Cache Files:

1. Ensure that the KRB5CCNAME variable is present in your environment.
2. Set KRB5CCNAME to a path that points to your credential cache file. (For example, C:\krb_cache\krb5cc_0 or /tmp/krb5cc_0.) The credential cache file is created when you use the MIT Kerberos Ticket Manager to generate your ticket.

3. To obtain a ticket:

   1. Open the MIT Kerberos Ticket Manager application.
   2. Click Get Ticket.
   3. Enter your principal name and password.
   4. Click OK.

   If the ticket is successfully obtained, the ticket information appears in Kerberos Ticket Manager and is stored in the credential cache file.

The connector uses the cache file to obtain the Kerberos ticket to connect to HDFS.

Keytab File

If your environment lacks the KRB5CCNAME environment variable, you can retrieve a Kerberos ticket using a Keytab File.

To use this method, set the User property to the desired username, and set the KerberosKeytabFile property to a file path pointing to the keytab file associated with the user.

User and Password

If your environment lacks the KRB5CCNAME environment variable and the KerberosKeytabFile property has not been set, you can retrieve a ticket using a user and password combination.

To use this method, set the User and Password properties to the user/password combination that you use to authenticate with HDFS.

Enable Cross-Realm Authentication¶

More complex Kerberos environments can require cross-realm authentication where multiple realms and KDC servers are used. For example, they might use one realm/KDC for user authentication, and another realm/KDC for obtaining the service ticket.

To enable this kind of cross-realm authentication, set the KerberosRealm and KerberosKDC properties to the values required for user authentication. Also, set the KerberosServiceRealm and KerberosServiceKDC properties to the values required to obtain the service ticket.

Important Notes¶

Configuration Files and Their Paths¶

• All references to adding configuration files and their paths refer to files and locations on the Harmony Agent where the connector is installed. These paths are to be adjusted as appropriate depending on the agent and the operating system. If multiple agents are used in an agent group, identical files will be required on each agent.

Advanced Features¶

This section details a selection of advanced features of the HDFS connector.

User Defined Views

The connector allows you to define virtual tables, called user defined views, whose contents are decided by a pre-configured query. These views are useful when you cannot directly control queries being issued to the drivers. See User Defined Views for an overview of creating and configuring custom views.

SSL Configuration

Use SSL Configuration to adjust how connector handles TLS/SSL certificate negotiations. You can choose from various certificate formats; see the SSLServerCert property under "Connection String Options" for more information.

Proxy

To configure the connector using private agent proxy settings, select the Use Proxy Settings checkbox on the connection configuration screen.

Query Processing

The connector offloads as much of the SELECT statement processing as possible to HDFS and then processes the rest of the query in memory (client-side).

See Query Processing for more information.

User Defined Views¶

The HDFS connector allows you to define a virtual table whose contents are decided by a pre-configured query. These are called User Defined Views, which are useful in situations where you cannot directly control the query being issued to the driver, e.g. when using the driver from Jitterbit. The User Defined Views can be used to define predicates that are always applied. If you specify additional predicates in the query to the view, they are combined with the query already defined as part of the view.

There are two ways to create user defined views:

• Create a JSON-formatted configuration file defining the views you want.
• DDL statements.

Define Views Using a Configuration File¶

User Defined Views are defined in a JSON-formatted configuration file called UserDefinedViews.json. The connector automatically detects the views specified in this file.

You can also have multiple view definitions and control them using the UserDefinedViews connection property. When you use this property, only the specified views are seen by the connector.

This User Defined View configuration file is formatted as follows:

• Each root element defines the name of a view.
• Each root element contains a child element, called query, which contains the custom SQL query for the view.

For example:

{
    "MyView": {
        "query": "SELECT * FROM Files WHERE MyColumn = 'value'"
    },
    "MyView2": {
        "query": "SELECT * FROM MyTable WHERE Id IN (1,2,3)"
    }
}

Use the UserDefinedViews connection property to specify the location of your JSON configuration file. For example:

"UserDefinedViews", "C:\Users\yourusername\Desktop\tmp\UserDefinedViews.json"

Define Views Using DDL Statements¶

The connector is also capable of creating and altering the schema via DDL Statements such as CREATE LOCAL VIEW, ALTER LOCAL VIEW, and DROP LOCAL VIEW.

Create a View¶

To create a new view using DDL statements, provide the view name and query as follows:

CREATE LOCAL VIEW [MyViewName] AS SELECT * FROM Customers LIMIT 20;

If no JSON file exists, the above code creates one. The view is then created in the JSON configuration file and is now discoverable. The JSON file location is specified by the UserDefinedViews connection property.

Alter a View¶

To alter an existing view, provide the name of an existing view alongside the new query you would like to use instead:

ALTER LOCAL VIEW [MyViewName] AS SELECT * FROM Customers WHERE TimeModified > '3/1/2020';

The view is then updated in the JSON configuration file.

Drop a View¶

To drop an existing view, provide the name of an existing schema alongside the new query you would like to use instead.

DROP LOCAL VIEW [MyViewName]

This removes the view from the JSON configuration file. It can no longer be queried.

Schema for User Defined Views¶

User Defined Views are exposed in the UserViews schema by default. This is done to avoid the view's name clashing with an actual entity in the data model. You can change the name of the schema used for UserViews by setting the UserViewsSchemaName property.

Work with User Defined Views¶

For example, a SQL statement with a User Defined View called UserViews.RCustomers only lists customers in Raleigh:

SELECT * FROM Customers WHERE City = 'Raleigh';

An example of a query to the driver:

SELECT * FROM UserViews.RCustomers WHERE Status = 'Active';

Resulting in the effective query to the source:

SELECT * FROM Customers WHERE City = 'Raleigh' AND Status = 'Active';

That is a very simple example of a query to a User Defined View that is effectively a combination of the view query and the view definition. It is possible to compose these queries in much more complex patterns. All SQL operations are allowed in both queries and are combined when appropriate.

SSL Configuration¶

Customize the SSL Configuration¶

By default, the connector attempts to negotiate SSL/TLS by checking the server's certificate against the system's trusted certificate store.

To specify another certificate, see the SSLServerCert property for the available formats to do so.

Data Model¶

The HDFS connector models HDFS objects as relational tables and views. HDFS objects have relationships to other objects; in the tables, these relationships are expressed through foreign keys. The following sections show the available API objects and provide more information on executing SQL to HDFS APIs.

Schemas for most database objects are defined in simple, text-based configuration files.

Key Features

• The connector models HDFS entities such as files and permissions as relational views, allowing you to write SQL to query HDFS data.
• Stored procedures allow you to execute operations to HDFS
• Live connectivity to these objects means any changes to your HDFS account are immediately reflected when using the connector.

Views¶

Views are similar to tables in the way that data is represented; however, views are read-only.

Queries can be executed against a view as if it were a normal table.

HDFS Connector Views¶

Files¶

Lists the contents of the supplied path.

Table Specific Information¶

Select¶

This will return a list of all the files and directories in your system. By default all subfolders are recursively scanned to list their children. You can configure the depth of subfolders you want to be recursively scanned with DirectoryRetrievalDepth property. All filters are executed client side within the connector.

Columns¶

Permissions¶

Lists the permissions of the files/file specified in the path.

Table Specific Information¶

Select¶

This will return a list of permissions of all the files and directories in your system. All filters are executed client side within the connector.

Columns¶

Stored Procedures¶

Stored procedures are function-like interfaces that extend the functionality of the connector beyond simple SELECT operations with HDFS.

Stored procedures accept a list of parameters, perform their intended function, and then return any relevant response data from HDFS, along with an indication of whether the procedure succeeded or failed.

HDFS Connector Stored Procedures¶

AppendToFile¶

Create and Write to a File.

Input¶

Result Set Columns¶

Concat¶

Concatenate a group of files to another file.

Input¶

Result Set Columns¶

CreateSnapshot¶

Create a Snapshot of a folder.

Input¶

Result Set Columns¶

CreateSymLink¶

Create a Symbolic Link.

Input¶

Result Set Columns¶

DeleteFile¶

Delete a file or a directory.

Input¶

Result Set Columns¶

DeleteSnapshot¶

Create a Snapshot of a folder.

Input¶

Result Set Columns¶

DownloadFile¶

Open and read a file.

Input¶

Result Set Columns¶

GetContentSummary¶

Get the content summary of a file/folder.

Input¶

Result Set Columns¶

GetFileChecksum¶

Get the checksum of a file.

Input¶

Result Set Columns¶

GetHomeDirectory¶

Get the home directory for the current user.

Result Set Columns¶

GetTrashRoot¶

Get the root directory of Trash for current user when the path specified is deleted.

Input¶

Result Set Columns¶

ListStatus¶

Lists the contents of the supplied path.

Input¶

Result Set Columns¶

MakeDirectory¶

Create a directory in the specified path.

Input¶

Result Set Columns¶

RenameFile¶

Rename a file or a directory.

Input¶

Result Set Columns¶

RenameSnapshot¶

Rename a Snapshot of a folder.

Input¶

Result Set Columns¶

SetOwner¶

Set owner and group of a path.

Input¶

Result Set Columns¶

SetPermission¶

Set permission of a path.

Input¶

Result Set Columns¶

TruncateFile¶

Truncate a file to a new length.

Input¶

Result Set Columns¶

UploadFile¶

Create and Write to a File.

Input¶

Result Set Columns¶

System Tables¶

You can query the system tables described in this section to access schema information, information on data source functionality, and batch operation statistics.

Schema Tables¶

The following tables return database metadata for HDFS:

• sys_catalogs: Lists the available databases.
• sys_schemas: Lists the available schemas.
• sys_tables: Lists the available tables and views.
• sys_tablecolumns: Describes the columns of the available tables and views.
• sys_procedures: Describes the available stored procedures.
• sys_procedureparameters: Describes stored procedure parameters.
• sys_keycolumns: Describes the primary and foreign keys.
• sys_indexes: Describes the available indexes.

Data Source Tables¶

The following tables return information about how to connect to and query the data source:

• sys_connection_props: Returns information on the available connection properties.
• sys_sqlinfo: Describes the SELECT queries that the connector can offload to the data source.

Query Information Tables¶

The following table returns query statistics for data modification queries:

• sys_identity: Returns information about batch operations or single updates.

sys_catalogs¶

Lists the available databases.

The following query retrieves all databases determined by the connection string:

SELECT * FROM sys_catalogs

Columns¶

sys_schemas¶

Lists the available schemas.

The following query retrieves all available schemas:

SELECT * FROM sys_schemas

Columns¶

sys_tables¶

Lists the available tables.

The following query retrieves the available tables and views:

SELECT * FROM sys_tables

Columns¶

sys_tablecolumns¶

Describes the columns of the available tables and views.

The following query returns the columns and data types for the Files table:

SELECT ColumnName, DataTypeName FROM sys_tablecolumns WHERE TableName='Files'

Columns¶

sys_procedures¶

Lists the available stored procedures.

The following query retrieves the available stored procedures:

SELECT * FROM sys_procedures

Columns¶

sys_procedureparameters¶

Describes stored procedure parameters.

The following query returns information about all of the input parameters for the Open stored procedure:

SELECT * FROM sys_procedureparameters WHERE ProcedureName='Open' AND Direction=1 OR Direction=2

Columns¶

sys_keycolumns¶

Describes the primary and foreign keys.

The following query retrieves the primary key for the Files table:

SELECT * FROM sys_keycolumns WHERE IsKey='True' AND TableName='Files'

Columns¶

sys_foreignkeys¶

Describes the foreign keys.

The following query retrieves all foreign keys which refer to other tables:

SELECT * FROM sys_foreignkeys WHERE ForeignKeyType = 'FOREIGNKEY_TYPE_IMPORT'

Columns¶

sys_primarykeys¶

Describes the primary keys.

The following query retrieves the primary keys from all tables and views:

SELECT * FROM sys_primarykeys

Columns¶

sys_indexes¶

Describes the available indexes. By filtering on indexes, you can write more selective queries with faster query response times.

The following query retrieves all indexes that are not primary keys:

SELECT * FROM sys_indexes WHERE IsPrimary='false'

Columns¶

sys_connection_props¶

Returns information on the available connection properties and those set in the connection string.

When querying this table, the config connection string should be used:

jdbc:cdata:hdfs:config:

This connection string enables you to query this table without a valid connection.

The following query retrieves all connection properties that have been set in the connection string or set through a default value:

SELECT * FROM sys_connection_props WHERE Value <> ''

Columns¶

sys_sqlinfo¶

Describes the SELECT query processing that the connector can offload to the data source.

Discovering the Data Source's SELECT Capabilities¶

Below is an example data set of SQL capabilities. Some aspects of SELECT functionality are returned in a comma-separated list if supported; otherwise, the column contains NO.

The following query retrieves the operators that can be used in the WHERE clause:

SELECT * FROM sys_sqlinfo WHERE Name = 'SUPPORTED_OPERATORS'

Note that individual tables may have different limitations or requirements on the WHERE clause; refer to the Data Model section for more information.

Columns¶

sys_identity¶

Returns information about attempted modifications.

The following query retrieves the Ids of the modified rows in a batch operation:

SELECT * FROM sys_identity

Columns¶

sys_information¶

Describes the available system information.

The following query retrieves all columns:

SELECT * FROM sys_information

Columns¶

Advanced Configurations Properties¶

The advanced configurations properties are the various options that can be used to establish a connection. This section provides a complete list of the options you can configure. Click the links for further details.

Authentication

Connection

Kerberos

SSL

Schema

Miscellaneous

Authentication¶

This section provides a complete list of authentication properties you can configure.

AuthScheme¶

The scheme used for authentication. Accepted entries are None, and Negotiate (Kerberos). None is the default.

Possible Values¶

None, Negotiate, Token

Data Type¶

string

Default Value¶

None

Remarks¶

This field is used to authenticate against the server. Use the following options to select your authentication scheme:

• None: Set this to use anonymous authentication and connect to the HDFS data source without specifying the user credentials.
• Negotiate: If AuthScheme is set to Negotiate, the connector will negotiate an authentication mechanism with the server. Set AuthScheme to Negotiate if you want to use Kerberos authentication.
• Token: Set this to authenticate using an AccessToken.

Host¶

This property specifies the host of your HDFS installation.

Data Type¶

string

Default Value¶

""

Remarks¶

This property specifies the host of your HDFS installation.

Port¶

This property specifies the port of your HDFS installation.

Data Type¶

string

Default Value¶

50070

Remarks¶

This property specifies the port of your HDFS installation.

User¶

The user name to login to the HDFS server.

Data Type¶

string

Default Value¶

""

Remarks¶

The user name to login to the HDFS server. If AuthScheme=None, it is used as the authenticated user. If AuthScheme=Negotiate, it is used in the Kerberos Authentication as a client principal.

Password¶

The password used to authenticate to the HDFS server. Only used when Kerberos authentication is selected.

Data Type¶

string

Default Value¶

""

Remarks¶

The password used to authenticate to the HDFS server. Only used when Kerberos authentication is selected.

AccessToken¶

The HDFS Access Token.

Data Type¶

string

Default Value¶

""

Remarks¶

The HDFS Access Token used to authenticate the requests.

UseSSL¶

This field sets whether SSL is enabled.

Data Type¶

bool

Default Value¶

false

Remarks¶

This field sets whether the connector will attempt to negotiate TLS/SSL connections to the server. By default, the connector checks the server's certificate against the system's trusted certificate store. To specify another certificate, set SSLServerCert.

Connection¶

This section provides a complete list of connection properties you can configure.

Path¶

This property specifies the HDFS path which will be used as the working directory.

Data Type¶

string

Default Value¶

""

Remarks¶

This property specifies the HDFS path which will be used as the working directory. Used in views Files and Permissions.

DirectoryRetrievalDepth¶

Limit the subfolders recursively scanned.

Data Type¶

int

Default Value¶

-1

Remarks¶

DirectoryRetrievalDepth specifies how many subfolders will be recursively scanned before stopping. -1 specifies that all subfolders are scanned. 0 specifies that only the current folder will be scanned for items.

Kerberos¶

This section provides a complete list of Kerberos properties you can configure.

KerberosKDC¶

The Kerberos Key Distribution Center (KDC) service used to authenticate the user.

Data Type¶

string

Default Value¶

""

Remarks¶

The Kerberos properties are used when using SPNEGO or Windows Authentication. The connector will request session tickets and temporary session keys from the Kerberos KDC service. The Kerberos KDC service is conventionally colocated with the domain controller.

If Kerberos KDC is not specified, the connector will attempt to detect these properties automatically from the following locations:

• KRB5 Config File (krb5.ini/krb5.conf): If the KRB5_CONFIG environment variable is set and the file exists, the connector will obtain the KDC from the specified file. Otherwise, it will attempt to read from the default MIT location based on the OS: C:\ProgramData\MIT\Kerberos5\krb5.ini (Windows) or /etc/krb5.conf (Linux).
• Java System Properties: Using the system properties java.security.krb5.realm and java.security.krb5.kdc.
• Domain Name and Host: If the Kerberos Realm and Kerberos KDC could not be inferred from another location, the connector will infer them from the configured domain name and host.

KerberosRealm¶

The Kerberos Realm used to authenticate the user.

Data Type¶

string

Default Value¶

""

Remarks¶

The Kerberos properties are used when using SPNEGO or Windows Authentication. The Kerberos Realm is used to authenticate the user with the Kerberos Key Distribution Service (KDC). The Kerberos Realm can be configured by an administrator to be any string, but conventionally it is based on the domain name.

If Kerberos Realm is not specified, the connector will attempt to detect these properties automatically from the following locations:

• KRB5 Config File (krb5.ini/krb5.conf): If the KRB5_CONFIG environment variable is set and the file exists, the connector will obtain the default realm from the specified file. Otherwise, it will attempt to read from the default MIT location based on the OS: C:\ProgramData\MIT\Kerberos5\krb5.ini (Windows) or /etc/krb5.conf (Linux)
• Java System Properties: Using the system properties java.security.krb5.realm and java.security.krb5.kdc.
• Domain Name and Host: If the Kerberos Realm and Kerberos KDC could not be inferred from another location, the connector will infer them from the user-configured domain name and host. This might work in some Windows environments.

KerberosSPN¶

The service principal name (SPN) for the Kerberos Domain Controller.

Data Type¶

string

Default Value¶

""

Remarks¶

If the SPN on the Kerberos Domain Controller is not the same as the URL that you are authenticating to, use this property to set the SPN.

KerberosKeytabFile¶

The Keytab file containing your pairs of Kerberos principals and encrypted keys.

Data Type¶

string

Default Value¶

""

Remarks¶

The Keytab file containing your pairs of Kerberos principals and encrypted keys.

KerberosServiceRealm¶

The Kerberos realm of the service.

Data Type¶

string

Default Value¶

""

Remarks¶

The KerberosServiceRealm is the specify the service Kerberos realm when using cross-realm Kerberos authentication.

In most cases, a single realm and KDC machine are used to perform the Kerberos authentication and this property is not required.

This property is available for complex setups where a different realm and KDC machine are used to obtain an authentication ticket (AS request) and a service ticket (TGS request).

KerberosServiceKDC¶

The Kerberos KDC of the service.

Data Type¶

string

Default Value¶

""

Remarks¶

The KerberosServiceKDC is used to specify the service Kerberos KDC when using cross-realm Kerberos authentication.

In most cases, a single realm and KDC machine are used to perform the Kerberos authentication and this property is not required.

This property is available for complex setups where a different realm and KDC machine are used to obtain an authentication ticket (AS request) and a service ticket (TGS request).

KerberosTicketCache¶

The full file path to an MIT Kerberos credential cache file.

Data Type¶

string

Default Value¶

""

Remarks¶

This property can be set if you wish to use a credential cache file that was created using the MIT Kerberos Ticket Manager or kinit command.

SSL¶

This section provides a complete list of SSL properties you can configure.

SSLServerCert¶

The certificate to be accepted from the server when connecting using TLS/SSL.

Data Type¶

string

Default Value¶

""

Remarks¶

If using a TLS/SSL connection, this property can be used to specify the TLS/SSL certificate to be accepted from the server. Any other certificate that is not trusted by the machine is rejected.

This property can take the following forms:

If not specified, any certificate trusted by the machine is accepted.

Certificates are validated as trusted by the machine based on the System's trust store. The trust store used is the 'javax.net.ssl.trustStore' value specified for the system. If no value is specified for this property, Java's default trust store is used (for example, JAVA_HOME\lib\security\cacerts).

Use '*' to signify to accept all certificates. Note that this is not recommended due to security concerns.

Schema¶

This section provides a complete list of schema properties you can configure.

Location¶

A path to the directory that contains the schema files defining tables, views, and stored procedures.

Data Type¶

string

Default Value¶

%APPDATA%\HDFS Data Provider\Schema

Remarks¶

The path to a directory which contains the schema files for the connector (.rsd files for tables and views, .rsb files for stored procedures). The folder location can be a relative path from the location of the executable. The Location property is only needed if you want to customize definitions (for example, change a column name, ignore a column, and so on) or extend the data model with new tables, views, or stored procedures.

If left unspecified, the default location is "%APPDATA%\HDFS Data Provider\Schema" with %APPDATA% being set to the user's configuration directory:

BrowsableSchemas¶

This property restricts the schemas reported to a subset of the available schemas. For example, BrowsableSchemas=SchemaA,SchemaB,SchemaC.

Data Type¶

string

Default Value¶

""

Remarks¶

Listing the schemas from databases can be expensive. Providing a list of schemas in the connection string improves the performance.

Tables¶

This property restricts the tables reported to a subset of the available tables. For example, Tables=TableA,TableB,TableC.

Data Type¶

string

Default Value¶

""

Remarks¶

Listing the tables from some databases can be expensive. Providing a list of tables in the connection string improves the performance of the connector.

This property can also be used as an alternative to automatically listing views if you already know which ones you want to work with and there would otherwise be too many to work with.

Specify the tables you want in a comma-separated list. Each table should be a valid SQL identifier with any special characters escaped using square brackets, double-quotes or backticks. For example, Tables=TableA,[TableB/WithSlash],WithCatalog.WithSchema.`TableC With Space`.

Note that when connecting to a data source with multiple schemas or catalogs, you will need to provide the fully qualified name of the table in this property, as in the last example here, to avoid ambiguity between tables that exist in multiple catalogs or schemas.

Views¶

Restricts the views reported to a subset of the available tables. For example, Views=ViewA,ViewB,ViewC.

Data Type¶

string

Default Value¶

""

Remarks¶

Listing the views from some databases can be expensive. Providing a list of views in the connection string improves the performance of the connector.

This property can also be used as an alternative to automatically listing views if you already know which ones you want to work with and there would otherwise be too many to work with.

Specify the views you want in a comma-separated list. Each view should be a valid SQL identifier with any special characters escaped using square brackets, double-quotes or backticks. For example, Views=ViewA,[ViewB/WithSlash],WithCatalog.WithSchema.`ViewC With Space`.

Note that when connecting to a data source with multiple schemas or catalogs, you will need to provide the fully qualified name of the table in this property, as in the last example here, to avoid ambiguity between tables that exist in multiple catalogs or schemas.

Miscellaneous¶

This section provides a complete list of miscellaneous properties you can configure.

MaxRows¶

Limits the number of rows returned when no aggregation or GROUP BY is used in the query. This takes precedence over LIMIT clauses.

Data Type¶

int

Default Value¶

-1

Remarks¶

Limits the number of rows returned when no aggregation or GROUP BY is used in the query. This takes precedence over LIMIT clauses.

Other¶

These hidden properties are used only in specific use cases.

Data Type¶

string

Default Value¶

""

Remarks¶

The properties listed below are available for specific use cases. Normal driver use cases and functionality should not require these properties.

Specify multiple properties in a semicolon-separated list.

Integration and Formatting¶

PseudoColumns¶

This property indicates whether or not to include pseudo columns as columns to the table.

Data Type¶

string

Default Value¶

""

Remarks¶

This setting is particularly helpful in Entity Framework, which does not allow you to set a value for a pseudo column unless it is a table column. The value of this connection setting is of the format "Table1=Column1, Table1=Column2, Table2=Column3". You can use the "*" character to include all tables and all columns; for example, "*=*".

Timeout¶

The value in seconds until the timeout error is thrown, canceling the operation.

Data Type¶

int

Default Value¶

60

Remarks¶

If Timeout = 0, operations do not time out. The operations run until they complete successfully or until they encounter an error condition.

If Timeout expires and the operation is not yet complete, the connector throws an exception.

UserDefinedViews¶

A filepath pointing to the JSON configuration file containing your custom views.

Data Type¶

string

Default Value¶

""

Remarks¶

User Defined Views are defined in a JSON-formatted configuration file called UserDefinedViews.json. The connector automatically detects the views specified in this file.

You can also have multiple view definitions and control them using the UserDefinedViews connection property. When you use this property, only the specified views are seen by the connector.

This User Defined View configuration file is formatted as follows:

• Each root element defines the name of a view.
• Each root element contains a child element, called query, which contains the custom SQL query for the view.

For example:

{
    "MyView": {
        "query": "SELECT * FROM Files WHERE MyColumn = 'value'"
    },
    "MyView2": {
        "query": "SELECT * FROM MyTable WHERE Id IN (1,2,3)"
    }
}

Use the UserDefinedViews connection property to specify the location of your JSON configuration file. For example:

"UserDefinedViews", C:\Users\yourusername\Desktop\tmp\UserDefinedViews.json

Note that the specified path is not embedded in quotation marks.