In the realm of EDB Postgres Advanced Server (EPAS) 16 databases, the UTL_FILE package stands as a cornerstone for interacting with the file system from EDB-SPL. This package offers a versatile set of subprograms for file operations, making it an invaluable tool for developers and DBAs alike. In this blog post, we will explore the capabilities of new submodules in UTL_FILE of EPAS 16, such as put_nchar, fgetpos, get_line_nchar, fgetattr, putf_nchar, put_line_nchar, fseek, and fopen_nchar, complete with examples.
What is UTL_FILE?
UTL_FILE is a built-in EDB-SPL package that facilitates reading from and writing to files on the server’s file system. It provides a collection of subprograms that can manage files, allowing for operations like file creation, reading, writing, and positioning.
Why is UTL_FILE Important?
The significance of UTL_FILE lies in its ability to bridge the gap between the database and the file system. It allows for:
- File System Integration: UTL_FILE bridges the gap between the EPAS and the server’s file system, allowing for more integrated and efficient data processing.
- Automation and Reporting: It’s essential for generating reports, logging, and automating file-based data exchange processes.
- Efficient Data Export/Import: Smoothly handle data transfers between the database and external files.
- Enhanced File Manipulation: Read, write, and modify files directly from the database.
How UTL_FILE is Changing the Landscape
The enhanced UTL_FILE package in EPAS 16 for developers and DBAs facilitates a more seamless and integrated approach to handling external files, especially in a multilingual context. This ability to directly read from and write to files using a variety of character sets, including NLS data, greatly simplifies data management tasks that involve external file interaction. The package’s capabilities in handling file attributes and positions further empower users to write more efficient and sophisticated file-handling EDB-SPL.
Exploring the Submodules with Examples
1. put_nchar
put_nchar writes a specified NCHAR string to a file.
CREATE OR REPLACE DIRECTORY "DIR" AS '/tmp';
DECLARE
file_handler UTL_FILE.FILE_TYPE;
BEGIN
file_handler := UTL_FILE.FOPEN_NCHAR('DIR', 'testfile.txt', 'W');
UTL_FILE.PUT_NCHAR(file_handler, N'Hello, World!');
UTL_FILE.FCLOSE(file_handler);
END;
2. fgetpos
fgetpos returns the current position of the file pointer.
CREATE OR REPLACE DIRECTORY "DIR" AS '/tmp';
DECLARE
file_handler UTL_FILE.FILE_TYPE;
pos INTEGER;
BEGIN
file_handler := UTL_FILE.FOPEN('DIR', 'testfile.txt', 'R');
UTL_FILE.FGETPOS(file_handler, pos);
DBMS_OUTPUT.PUT_LINE('Position: ' || pos);
UTL_FILE.FCLOSE(file_handler);
END;
3. get_line_nchar
get_line_nchar reads a line of NCHAR text from a file.
CREATE OR REPLACE DIRECTORY "DIR" AS '/tmp';
DECLARE
file_handler UTL_FILE.FILE_TYPE;
line NVARCHAR2(100);
BEGIN
file_handler := UTL_FILE.FOPEN_NCHAR('DIR', 'testfile.txt', 'R');
UTL_FILE.GET_LINE_NCHAR(file_handler, line);
DBMS_OUTPUT.PUT_LINE(line);
UTL_FILE.FCLOSE(file_handler);
END;
3. fgetattr
fgetattr retrieves attributes of a file, such as its size, existence, and read/write permissions.
CREATE OR REPLACE DIRECTORY "DIR" AS '/tmp';
DECLARE
fexists BOOLEAN;
file_len NUMBER;
blocksize NUMBER;
BEGIN
UTL_FILE.FGETATTR('DIR', 'testfile.txt', fexists, file_len, blocksize);
IF fexists THEN
DBMS_OUTPUT.PUT_LINE('File size: ' || file_len);
ELSE
DBMS_OUTPUT.PUT_LINE('File does not exist');
END IF;
END;
5. putf_nchar
putf_nchar writes formatted NCHAR text to a file.
CREATE OR REPLACE DIRECTORY "DIR" AS '/tmp';
DECLARE
file_handler UTL_FILE.FILE_TYPE;
BEGIN
file_handler := UTL_FILE.FOPEN_NCHAR('DIR', 'testfile.txt', 'W');
UTL_FILE.PUTF_NCHAR(file_handler, 'Name: %s, Age: %s', N'John', N'30');
UTL_FILE.FCLOSE(file_handler);
END;
6. put_line_nchar
put_line_nchar writes a line of NCHAR text, followed by an end-of-line marker.
CREATE OR REPLACE DIRECTORY "DIR" AS '/tmp';
DECLARE
file_handler UTL_FILE.FILE_TYPE;
BEGIN
file_handler := UTL_FILE.FOPEN_NCHAR('DIR', 'testfile.txt', 'W');
UTL_FILE.PUT_LINE_NCHAR(file_handler, N'Hello, World!');
UTL_FILE.FCLOSE(file_handler);
END;
7. fseek
fseek moves the file pointer to a specified position.
CREATE OR REPLACE DIRECTORY "DIR" AS '/tmp';
DECLARE
file_handler UTL_FILE.FILE_TYPE;
BEGIN
file_handler := UTL_FILE.FOPEN('DIR', 'testfile.txt', 'R');
UTL_FILE.FSEEK(file_handler, 100); -- Move pointer to 100th byte
UTL_FILE.FCLOSE(file_handler);
END;
8. fopen_nchar
fopen_nchar opens a file for NCHAR data processing.
CREATE OR REPLACE DIRECTORY "DIR" AS '/tmp';
DECLARE
file_handler UTL_FILE.FILE_TYPE;
BEGIN
file_handler := UTL_FILE.FOPEN_NCHAR('DIR', 'testfile.txt', 'W');
-- Perform file operations
UTL_FILE.FCLOSE(file_handler);
END;
Conclusion
UTL_FILE in EPAS offers a powerful suite of tools for file operations within the database environment. By leveraging these submodules, developers and DBAs can perform a wide range of file manipulation tasks, enhancing the overall capabilities of EPAS. Whether it’s for data export, report generation, or handling complex file-based operations, UTL_FILE stands as a pivotal feature in the Postgres database landscape.
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