Work with Cassandra Data in FoxPro



Load Cassandra data into a FoxPro database. This article includes full code and a walk-through of the process.

The CData ODBC driver for Cassandra enables you to access Cassandra data using the ODBC standard. You can use the CData ODBC Driver for Cassandra to integrate Cassandra data into your FoxPro project. The procedure below provides a walk-through of the included code sample, which saves Cassandra data into tables in a FoxPro database.

Connect to Cassandra as an ODBC Data Source

If you have not already, first specify connection properties in an ODBC DSN (data source name). This is the last step of the driver installation. You can use the Microsoft ODBC Data Source Administrator to create and configure ODBC DSNs.

NOTE: Set the 'Map To WVarchar' connection property to FALSE (FoxPro uses the ODBC W API and returns the WCHAR for the value type).

Set the Server, Port, and Database connection properties to connect to Cassandra. Additionally, to use internal authentication set the User and Password connection properties.

Connect and Transfer

To get started, add the code sample to a new project. You can execute the following command to save all tables without displaying them:

DO C:\Temp\sqldump.prg WITH "CData Cassandra Source", "TESTDB", .f.

Below is the process that the program follows:

  1. Create a new FoxPro database.
  2. Open a connection to Cassandra data with the line below:

    m.hSQLconnection = SQLCONNECT(m.cODBCDSN)
  3. If the connection was successful, you can now retrieve the list of tables using the SQLTABLES function. The code below saves the list of tables in sys_tables.dbf:

    WAIT WINDOW "Fetching tables for data source '" + m.cODBCDSN + "'..." NOWAIT NOCLEAR m.nSQLTABLES = SQLTABLES(m.hSQLconnection) IF lUseDistinctConnections WAIT WINDOW "Closing ODBC Connection for data source '" + m.cODBCDSN + "'..." NOWAIT NOCLEAR SQLDISCONNECT(m.hSQLconnection) m.hSQLconnection = 0 * SQLCONNECT needs to be called again ENDIF IF m.nSQLTABLES > 0 * create local table containing list of tables in db COPY TO (m.cImportData + "sys_tables") USE * convert each table to DBF USE (m.cImportData + "sys_tables") ALTER TABLE DBF("sys_tables") ; ADD COLUMN records i ; ADD COLUMN dbfname m
  4. Scan over each table, saving it to a DBF file. The function ODBCtoDBF stores the table in a DBF file and then opens a grid if the lBrowse parameter is set to true: FUNCTION ODBCtoDBF (cTableName as String, cTableType as String, lBrowse as Logical, lhSQLConnection as Integer) WAIT WINDOW ; "Converting " + m.cTableType + ' "' + m.cTableName + '" to DBF...' ; NOWAIT NOCLEAR ACTIVATE SCREEN * strip characters incompatible with FoxPro out of the name of the DBF file m.cTableAlias = "" m.nTableNameLen = LEN(m.cTableName) m.nTableNameStart = 1 FOR m.nTableNameStart = 1 TO m.nTableNameLen m.cCharacter = SUBSTR(m.cTableName, m.nTableNameStart, 1) IF !ISALPHA(m.cCharacter) .and. (m.nTableNameStart = 1 .or. !ISDIGIT(m.cCharacter)) m.cTableAlias = m.cTableAlias + "_" ELSE m.cTableAlias = m.cTableAlias + m.cCharacter ENDIF ENDFOR m.cFromTable = m.cTableName m.cTempViewAlias = m.cTableType + "_" + m.cTableAlias LOCAL loException as Exception LOCAL lnResultSets TRY * run query m.lnResultSets = SQLEXEC(m.lhSQLConnection, ; "SELECT * FROM " + m.cFromTable, ; m.cTempViewAlias, ; aSQLResult) IF m.lnResultSets#1 SET STEP ON ENDIF ACTIVATE SCREEN CATCH TO m.loException ACTIVATE SCREEN ? "Error opening " + m.cTempViewAlias + ":" ? m.loException.Message ? m.loException.Details ENDTRY IF !USED(m.cTempViewAlias) RETURN ENDIF * copy records from view cursor to disk SELECT * FROM (m.cTempViewAlias) ; INTO TABLE (m.cImportData + m.cTableAlias) IF USED(m.cTableAlias) ACTIVATE SCREEN FLUSH && flush the buffer to write the data to disk IF m.lBrowse * pop the table up on screen SELECT (m.cTableAlias) BROWSE NORMAL NOMODIFY NOWAIT ACTIVATE SCREEN ELSE * close on-disk table for now USE IN (m.cTableAlias) ACTIVATE SCREEN ENDIF ENDIF IF USED(m.cTempViewAlias) USE IN &cTempViewAlias && close SQL view ACTIVATE SCREEN ENDIF WAIT CLEAR ENDFUNC
  5. You can now save tables of Cassandra data as DBF files.

Below is the full code, in FoxPro 9 syntax:

PARAMETERS cODBCDSN, cDatabaseName, lBrowseAfterConvert * cODBCDSN The ODBC data source name, used for the name of the folder where the DBF tables are stored. * cDatabaseName The name of the FoxPro database to use. This database is created if it does not exist. The default is DATABASE_NAME. * * lBrowseAfterConvert If ".t." display each table with the BROWSE command after importing it. If ".f." close each table before moving on to the next one. #define ODBC_DATASOURCE "DataSourceName" #define DATABASE_NAME "odbcdata" m.m_tpath = ".\" && root directory for data ON ERROR SET SAFETY OFF IF VARTYPE(m.cODBCDSN)#"C" .or. EMPTY(m.cODBCDSN) m.cODBCDSN = ODBC_DATASOURCE ENDIF IF VARTYPE(m.cDatabaseName)#"C" .or. EMPTY(m.cDatabaseName) m.cDatabaseName = DATABASE_NAME ENDIF m.cImportData = m.cODBCDSN + "\" CLOSE TABLES ALL CLOSE DATABASES ALL IF !DIRECTORY(m.cImportData) MKDIR (m.cImportData) ENDIF CREATE DATABASE (m.cDatabaseName) CREATE CONNECTION (m.cDatabaseName) DATASOURCE (m.cODBCDSN) DATABASE (m.cDatabaseName) WAIT WINDOW "Opening ODBC Connection for data source '" + m.cODBCDSN + "'..." NOWAIT NOCLEAR m.hSQLconnection = SQLCONNECT(m.cODBCDSN) IF m.hSQLconnection > 0 * Connection successful; get list of tables WAIT WINDOW "Fetching tables for data source '" + m.cODBCDSN + "'..." NOWAIT NOCLEAR m.nSQLTABLES = SQLTABLES(m.hSQLconnection) IF m.nSQLTABLES > 0 * Create local table containing list of tables in db COPY TO (m.cImportData + "sys_tables") USE * Convert each table to DBF USE (m.cImportData + "sys_tables") ALTER TABLE DBF("sys_tables") ; ADD COLUMN records i ; ADD COLUMN dbfname m SCAN m.cCurrentTable = TRIM(sys_tables.table_name) m.cCurrentTableType = TRIM(sys_tables.table_type) && Valid values are "SYSTEMTABLE", "TABLE", and "VIEW". IF m.cCurrentTableType = "TABLE" or m.cCurrentTableType = "VIEW" ODBCtoDBF(m.cCurrentTable, m.cCurrentTableType, m.lBrowseAfterConvert, m.hSQLConnection) ELSE ACTIVATE SCREEN ? "ERROR:", m.cCurrentTable, "Couldn't open ODBC connection." =MESSAGEBOX("couldn't open data source " + m.cODBCDSN + " for table " + m.cCurrentTable + ".") ENDIF ENDSCAN BROWSE NORMAL NOWAIT ELSE =MESSAGEBOX("No tables found in data source " + m.cODBCDSN + ".") SET STEP ON ENDIF SQLDISCONNECT(m.hSQLconnection) ELSE =MESSAGEBOX("Could not open data source " + m.cODBCDSN + ".") SET STEP ON ENDIF FUNCTION ODBCtoDBF (cTableName as String, cTableType as String, lBrowse as Logical, lhSQLConnection as Integer) WAIT WINDOW ; "Converting " + m.cTableType + ' "' + m.cTableName + '" to DBF...' ; NOWAIT NOCLEAR ACTIVATE SCREEN * Strip characters incompatible with FoxPro out of the name of the DBF file m.cTableAlias = "" m.nTableNameLen = LEN(m.cTableName) m.nTableNameStart = 1 FOR m.nTableNameStart = 1 TO m.nTableNameLen m.cCharacter = SUBSTR(m.cTableName, m.nTableNameStart, 1) IF !ISALPHA(m.cCharacter) .and. (m.nTableNameStart = 1 .or. !ISDIGIT(m.cCharacter)) m.cTableAlias = m.cTableAlias + "_" ELSE m.cTableAlias = m.cTableAlias + m.cCharacter ENDIF ENDFOR m.cFromTable = m.cTableName m.cTempViewAlias = m.cTableType + "_" + m.cTableAlias LOCAL loException as Exception LOCAL lnResultSets TRY * Run query m.lnResultSets = SQLEXEC(m.lhSQLConnection, ; "SELECT * FROM " + m.cFromTable, ; m.cTempViewAlias, ; aSQLResult) IF m.lnResultSets#1 SET STEP ON ENDIF ACTIVATE SCREEN CATCH TO m.loException ACTIVATE SCREEN ? "Error opening " + m.cTempViewAlias + ":" ? m.loException.Message ? m.loException.Details ENDTRY IF !USED(m.cTempViewAlias) RETURN ENDIF * Copy records from view cursor to disk SELECT * FROM (m.cTempViewAlias) ; INTO TABLE (m.cImportData + m.cTableAlias) IF USED(m.cTableAlias) ACTIVATE SCREEN FLUSH && Flush the buffer to write the data to disk IF m.lBrowse * Display the table on screen SELECT (m.cTableAlias) BROWSE NORMAL NOMODIFY NOWAIT ACTIVATE SCREEN ELSE * Close on-disk table USE IN (m.cTableAlias) ACTIVATE SCREEN ENDIF ENDIF IF USED(m.cTempViewAlias) USE IN &cTempViewAlias && Close SQL view ACTIVATE SCREEN ENDIF WAIT CLEAR ENDFUNC

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Apache Cassandra Icon Cassandra ODBC Driver

The Apache Cassandra ODBC Driver is a powerful tool that allows you to connect with live data from Apache Cassandra NoSQL database, directly from any applications that support ODBC connectivity.

Access Cassandra data like you would a database - read, write, and update NoSQL tables through a standard ODBC Driver interface.