Configuring a Data Source in the Linux OS

Procedure

1. Install unixODBC. (By default, the unixODBC source code package has been obtained during environment preparation.) It does not matter if unixODBC of another version has been installed.
   For example, install unixODBC-2.3.7.

   tar zxvf unixODBC-2.3.7.tar.gz
   cd unixODBC-2.3.7
   
   ./configure --enable-gui=no # To perform compilation on an Arm server, add the configure parameter --build=aarch64-unknown-linux-gnu.
   make
   # The installation may require root permissions.
   make install

   

   • Currently, unixODBC-2.2.1 is not supported.
   • By default, it is installed in the /usr/local directory. The data source file is generated in the /usr/local/etc directory, and the library file is generated in the /usr/local/lib directory.
   • You can compile unixODBC with the --enable-fastvalidate=yes option to achieve higher performance. However, this option may cause an application that passes an invalid handle to the ODBC API to fail instead of returning an SQL_INVALID_HANDLE error.

2. Replace the GaussDB client driver.

   Decompress GaussDB-Kernel_Database version number_OS information_64bit_Odbc.tar.gz. After the decompression, the lib and odbc folders are generated. The odbc folder contains another lib folder. Copy all dynamic libraries in the /lib and /odbc/lib folders to the /usr/local/lib directory.

3. Configure a data source.
   1. Configure the ODBC driver file.

      Add the following content to the /usr/local/etc/odbcinst.ini file:

      [GaussMPP]
      Driver64=/usr/local/lib/psqlodbcw.so
      setup=/usr/local/lib/psqlodbcw.so

      For descriptions of the parameters in the odbcinst.ini file, see Table 1.

      Table 1 odbcinst.ini configuration parameters

      Parameter	Description	Example
      [DriverName]	Driver name, corresponding to the driver in DSN.	[GaussMPP]
      Driver64	Path of the dynamic driver library.	Driver64=/usr/local/lib/psqlodbcw.so
      setup	Driver installation path, which is the same as the dynamic library path in Driver64.	setup=/usr/local/lib/psqlodbcw.so

   2. Configure the data source file.

      Add the following content to the /usr/local/etc/odbc.ini file:

      [gaussdb]
      Driver=GaussMPP
      Servername=127.0.0.1 (database server IP address)
      Database=postgres  (database name)
      Username=omm  (database username)
      Password=  (database user password)
      Port=8000 (database listening port)
      Sslmode=allow

      For descriptions of the parameters in the odbc.ini file, see Table 2.

      Table 2 odbc.ini configuration parameters

      Parameter	Description	Example
      [DSN]	Data source name.	[gaussdb]
      Driver	Driver name, corresponding to DriverName in odbcinst.ini.	Driver=GaussMPP
      Servername	Server IP address. Multiple IP addresses can be configured.	Servername=127.0.0.1
      Database	Name of the database to connect to.	Database = postgres
      Username	Database username.	Username=omm
      Password	Password of the database user. NOTE: After a user establishes a connection, the ODBC driver automatically clears their password stored in memory. However, if this parameter is configured, unixODBC will cache data source files, which may cause the password to be stored in the memory for a long time. When you connect to an application, you are advised to send your password through an API instead of writing it in a data source configuration file. After the connection has been established, immediately clear the memory segment where your password is stored. NOTICE: The password in the configuration file must comply with the following HTTP rules: Characters must comply with the URL encoding specifications. For example, the exclamation mark (!) must be written as %21, and the percent sign (%) must be written as %25. Therefore, pay attention to the characters. A plus sign (+) will be replaced by a space.	Password=********
      Port	Port number of the server. When load balancing is enabled, multiple port numbers can be configured and must correspond to multiple IP addresses. If multiple IP addresses are configured and only one port number is configured when load balancing is enabled, all IP addresses share the same port number by default, that is, the configured port number.	Port=8000
      Sslmode	Specifies whether to enable the SSL connection. NOTE: For details about the values of the Sslmode option, see Table 3.	Sslmode = allow
      Debug	Specifies whether to enable the debugging mode. Value range: 0 to INT_MAX. If this parameter is set to 0, the function is disabled. If this parameter is set to a value greater than 0, the mylog file of the psqlODBC driver will be printed. The directory generated for storing logs is /tmp/. The default value is 0.	Debug = 1
      UseServerSidePrepare	Specifies whether to enable the extended query protocol for the database. Value range: 0 and 1 If this parameter is set to 0, the function is disabled. If this parameter is set to 1, the function is enabled. The default value is 1.	UseServerSidePrepare = 1
      UseBatchProtocol	Specifies whether to enable the batch query protocol. If it is enabled, DML performance can be improved. Value range: 0 and 1 If this parameter is set to 0, the batch query protocol is disabled (mainly for communication with earlier database versions). If this parameter is set to 1 and support_batch_bind is set to on, the batch query protocol is enabled. The default value is 1.	UseBatchProtocol = 1
      ForExtensionConnector	Specifies whether the savepoint is sent. Value range: 0 and 1 If this parameter is set to 0, the savepoint is sent. If this parameter is set to 1, the savepoint is not sent. The default value is 1.	ForExtensionConnector = 1
      ConnectionExtraInfo	Specifies whether to display the driver deployment path and process owner in the GUC parameter connection_info. Value range: 0 and 1 If this parameter is set to 0, the information is not displayed. If this parameter is set to 1, the information is displayed. The default value is 0. NOTE: If this parameter is set to 1, the ODBC driver reports the driver deployment path and process owner to the database and displays the information in the GUC parameter connection_info. In this case, you can query the information from PG_STAT_ACTIVITY or PGXC_STAT_ACTIVITY.	ConnectionExtraInfo = 1
      BoolsAsChar	Specifies whether to process Boolean values as characters. Value range: 0 and 1 If this parameter is set to 0, the Boolean values are mapped to the SQL_BIT type. If this parameter is set to 1, the Boolean values are mapped to the SQL_CHAR type. The default value is 1.	BoolsAsChar = 1
      RowVersioning	Specifies whether to allow the application to check whether a row of data is modified by another user when the row of data is updated. Value range: 0 and 1 If this parameter is set to 0, application detection is not allowed. If this parameter is set to 1, application detection is allowed. The default value is 0.	RowVersioning=1
      ShowSystemTables	Specifies whether to regard the system catalog as a common SQL table by default. Value range: 0 and 1 If this parameter is set to 0, the driver does not regard the system catalog as a common SQL table by default. If this parameter is set to 1, the driver regards the system catalog as a common SQL table by default. The default value is 0.	ShowSystemTables=1
      AutoBalance	Specifies whether to enable ODBC load balancing. Value range: 0 and 1 If the value is 0, load balancing is disabled. If the value is 1, load balancing is enabled. The default value is 0.	AutoBalance=1
      RefreshCNListTime	Time for refreshing the CN list. This parameter can be configured when load balancing is enabled. The value is an integer, in seconds. Value range: 0 to INT_MAX. If the value is 0, this parameter is disabled. If the value is greater than 0, the value is the time for refreshing the CN list. The default value is 10.	RefreshCNListTime=5
      Priority	This parameter can be configured when load balancing is enabled. Value range: 0 and 1 If the value is 0, this parameter is disabled. If the value is 1, this parameter is enabled. The default value is 0. NOTE: When Priority is enabled, all connections initiated by applications are preferentially sent to the CNs configured in the configuration file. If all the configured CNs are unavailable, the connections are sent to the remaining CNs.	Priority=1
      UsingEip	This parameter can be configured when load balancing is enabled. Value range: 0 and 1 If the value is 0, this parameter is disabled. If the value is 1, it is enabled. The default value is 0. NOTE: This value specifies whether to use an elastic IP address for load balancing. If UsingEip is enabled, the elastic IP address is used for load balancing. If UsingEip is disabled, the data IP address is used for load balancing.	UsingEip=1
      MaxCacheQueries	Controls the number of prepared statements cached for each connection. Value range: 0 to 4096 The default value is 0. NOTE: If this parameter is set to 0, the prepared statement cache pool is disabled on the client. If this parameter is set to a value greater than 4096, the value 4096 is used. If the number of executed statements exceeds the upper limit specified by MaxCacheQueries, the least recently used statements are eliminated.	MaxCacheQueries=128
      MaxCacheSizeMiB	Controls the total size of prepared statements cached for each connection. This parameter takes effect when the value of MaxCacheQueries is greater than 0. Value range: 0 to 4096 The default value is 1. NOTE: If the total size of cached statements is greater than the value of MaxCacheSizeMiB, the least recently used statements are eliminated. If this parameter is set to a value greater than 4096, the value 4096 is used. The unit is MB.	MaxCacheSizeMiB=10
      TcpUserTimeout	Specifies the maximum duration for which transmitted data can remain unacknowledged before the TCP connection is forcibly closed on an OS that supports the TCP_USER_TIMEOUT socket option. Value range: 0 to INT_MAX. The default value is 0. NOTE: 0 indicates that the default value is used. Ignore this parameter for UDS connections. The unit is millisecond.	TcpUserTimeout=5000

      Table 3 Sslmode options

      Sslmode	Enable SSL Encryption	Description
      disable	No	SSL connection is not enabled.
      allow	Possible	If the database server requires SSL connection, SSL connection can be enabled. However, authenticity of the database server will not be verified.
      prefer	Possible	If the database supports SSL connection, SSL connection is preferred. However, authenticity of the database server will not be verified.
      require	Yes	SSL connection is required and data is encrypted. However, authenticity of the database server will not be verified.
      verify-ca	Yes	SSL connection is required and whether the database has a trusted certificate will be verified.
      verify-full	Yes	SSL connection is required. In addition to the check scope specified by verify-ca, the system checks whether the name of the host where the database resides is the same as that in the certificate. GaussDB does not support this mode.

      

      When establishing connections to the GaussDB server using ODBC, you can enable SSL connections to encrypt client and server communications. To enable SSL connection, you must have the server certificate, client certificate, and private key files. For details on how to obtain these files, see related documents and commands of OpenSSL.

4. Configure the environment variables on the client.

   vim ~/.bashrc

   Add the following information to the configuration file:

   export LD_LIBRARY_PATH=/usr/local/lib/:$LD_LIBRARY_PATH
   export ODBCSYSINI=/usr/local/etc
   export ODBCINI=/usr/local/etc/odbc.ini

5. Run the following command to validate the addition:

   source ~/.bashrc

6. Test the connection.

   After the installation, the generated binary file is stored in the /usr/bin directory. You can run the isql -v gaussdb command (gaussdb is the data source name).

   • If the following information is displayed, the configuration is correct and the connection succeeds:

     +---------------------------------------+
     | Connected!                            |
     |                                       |
     | sql-statement                         |
     | help [tablename]                      |
     | quit                                  |
     |                                       |
     +---------------------------------------+

   • If error information is displayed, the configuration is incorrect. Check the configuration.
   • In a cluster environment, you need to copy and configure the unixODBC file on all nodes.
   

   When ODBC is used to connect to a database, the kernel parameters are set as follows:

   SET extra_float_digits = 2;
   SET DateStyle = 'ISO';

   These parameters may cause the ODBC and gsql clients to display inconsistent data in aspects such as date data display mode and floating-point precision representation. If the result is not as expected, you are advised to explicitly set these parameters in the ODBC application code.

Troubleshooting

• [UnixODBC][Driver Manager]Can't open lib 'xxx/xxx/psqlodbcw.so':file not found.

  Possible causes:

  • The path configured in the odbcinst.ini file is incorrect.

    Run ls to check the path in the error information, ensuring that the psqlodbcw.so file exists and you have execution permissions on it.

  • The dependent library of psqlodbcw.so does not exist or is not in system environment variables.

    Run the ldd command to check the path in the error information. If the unixODBC library such as libodbc.so.1 is missing, reconfigure unixODBC according to the procedure, ensure that the lib directory in the installation path is added to LD_LIBRARY_PATH. If the problem persists after reinstallation, manually copy the content in the unixodbc/lib directory of the database installation package to the lib directory in the installation path of the unixODBC. If other libraries do not exist, add the lib directory under the ODBC driver package to LD_LIBRARY_PATH. If other standard libraries are missing, install them.

• [UnixODBC]connect to server failed: no such file or directory

  Possible causes:

  • An incorrect or unreachable database IP address or port was configured.

    Check the Servername and Port configuration items in data sources.

  • Server monitoring is improper.

    If Servername and Port are correctly configured, ensure the proper NIC and port are monitored by following the database server configurations in the procedure in this section.

  • Firewall and network gatekeeper settings are improper.

    Check firewall settings, and ensure that the database communication port is trusted.

    Check to ensure that network gatekeeper settings are proper (if any).

• [unixODBC]The password-stored method is not supported.

  Possible causes:

  The Sslmode configuration item is not configured in the data sources.

  Solution:

  Set the configuration item to allow or a higher level. For details, see Table 3.

• Server common name "xxxx" does not match host name "xxxxx"

  Possible causes:

  When verify-full is used for SSL encryption, the driver checks whether the host name in certificates is the same as the actual one.

  Solution:

  To solve this problem, use verify-ca to stop checking host names, or generate a set of server certificates containing the actual host names.

• Driver's SQLAllocHandle on SQL_HANDLE_DBC failed

  Possible causes:

  The executable file (such as the isql tool of unixODBC) and the database driver (psqlodbcw.so) depend on different library versions of ODBC, such as libodbc.so.1 and libodbc.so.2. You can verify this problem by using the following method:

  ldd `which isql` | grep odbc
  ldd psqlodbcw.so | grep odbc

  If the suffix digits of the outputs libodbc.so are different or indicate different physical disk files, this problem exists. Both isql and psqlodbcw.so require libodbc.so to be loaded. If they load different physical files, two sets of function lists with the same name are generated in a visible domain (the libodbc.so.* function export lists of unixODBC are the same). This results in conflicts and the database driver cannot be loaded.

  Solution:

  Uninstall the unnecessary unixODBC, such as libodbc.so.2, and create a soft link with the same name and the .so.2 suffix for the remaining libodbc.so.1 library.

• FATAL: Forbid remote connection with trust method!

  For security reasons, the database CN prevents unauthorized access from other nodes within the cluster.

  To access the CN from inside the cluster, deploy the ODBC program on the host where the CN is located and use 127.0.0.1 as the server address. It is recommended that the service system be deployed outside the cluster. If it is deployed inside, database performance may be affected.

• [unixODBC][Driver Manager]Invalid attribute value

  This problem occurs when you use SQL on other GaussDB. The possible cause is that the unixODBC version is not the recommended one. You are advised to run the odbcinst --version command to check the unixODBC version.

• authentication method 10 not supported.

  If this error occurs on an open-source client, the cause may be:

  The database stores only the SHA-256 hash of the password, but the open-source client supports only MD5 hashes.

  

  • The database stores the hashes of user passwords instead of actual passwords.
  • If a password is updated or a user is created, both types of hashes will be stored, compatible with open-source authentication protocols.
  • An MD5 hash can only be generated using the original password, but the password cannot be obtained by reversing its SHA-256 hash. Passwords in the source version will only have SHA-256 hashes and not support MD5 authentication.
  • MD5 has lower security and poses security risks. Therefore, you are advised to use a more secure cryptographic algorithm.

  To solve this problem, you can update the user password (see ALTER USER) or create a user (see CREATE USER) having the same permissions as the faulty user.

• unsupported frontend protocol 3.51: server supports 1.0 to 3.0

  The database version is too early or the database is an open-source database.

  Use the driver of the required version to connect to the database.

• FATAL: GSS authentication method is not allowed because XXXX user password is not disabled.

  In pg_hba.conf of the target CN, the authentication mode is set to gss for authenticating the IP address of the current client. However, this authentication algorithm cannot authenticate clients. Change the authentication algorithm to sha256 and try again.

• isql: error while loading shared libraries:xxx

  The dynamic library does not exist in the environment. You need to install the corresponding library.