MacLochlainns Weblog

Michael McLaughlin's Technical Blog

Site Admin

Archive for December, 2023

Oracle 23c Free SQL*Plus

without comments

It’s always frustrated me when using the sqlplus command-line interface (CLI) that you can’t just “up arrow” to through the history. At least, that’s the default case unless you wrap the sqlplus executable.

I like to do my development work as close to the database as possible. The delay from SQL Developer to the database or VSCode to the database is just too long. Therefore, I like the native sqlplus to be as efficient as possible. This post shows you how to install the rlwarp utility to wrap sqlplus and create a sandboxed student user for a local development account inside the Oracle 23c Free container. You should note that the Docker or Podman Container is using Oracle Unbreakable Linux 8 as it’s native OS.

You can connect to your Docker version of Oracle Database 23c Free with the following command:

docker exec -it -u root oracle23c bash

You can’t just use dnf to install rlwrap and get it to magically install all the dependencies. That would be too easy, eh?

Attempting to do so will lock your base OS and eventually force you to kill with prejudice the hung dnf process (at least it forced me to do so). You need to determine the rlwrap dependencies and then install them first. In that process, I noticed that the which utility program wasn’t installed in the container.

Naturally, I installed the which utility first with this command:

dnf install -y which

The rlwrap dependencies are: glibc, ncurses, perl, readline, python, and git. Only the perl, python, and git are missing from the list of formal dependencies but there’s another dependency the epel-release package.

If you want to verify whether a package is installed, you can use the rpm command like this:

rpm -qa | grep package_name

I installed the perl programming environment (a big install) with this command:

dnf install -y perl

I installed the python3 with this command:

dnf install -y python3

I installed the git module with this command:

dnf install -y git

I installed the epel-release container with this command:

dnf install -y epel-release

After installing all of these, you’re now ready to install the core rlwrap utility program. Like the other installations, you use:

dnf install -y rlwrap

At this point, you need to create a sandboxed user account for the Docker instance because as a developer using the root user for simple tasks is a bad idea. While you could do this with a Docker command, the Oracle 23c Free edition raised a lock on the /etc/group file when I tried it. Naturally, that’s not a problem because you can connect as the root user with this syntax:

docker exec -it -u root oracle23c bash

As the root user, create a student account as a developer account in the Oracle 23c Free container:

useradd -u 501 -g dba -G users -d /home/student -s /bin/bash/ -c "Student" -n student

You’ll be unable to leverage the tnsnames.ora file unless you alter the prior command to replace dba with oinstall or add the following command:

usermod -a -G oinstall student

Exit the Oracle 23c Free container as the root user and reconnect as the student user with this syntax:

docker exec -it --user student oracle23c bash

While you’re connected as the root user, you should create an upload directory as a subdirectory of the $ORACLE_BASE directory. The $ORACLE_BASE directory in the Oracle Database 23c Free Docker image is the /opt/oracle directory.

You should use the following syntax to create the upload directory and change its permission to that of the Oracle Database 23c Free installation (for a future blog post on developing external table deployment on the Docker image):

mkdir /opt/oracle
chown -R oracle:install /opt/oracle/upload

You also can add the following student function to the Ubuntu student user’s .bashrc file. It means all you need to type to connect to the Oracle Database 23c Free Docker instance is “student“. I like shortcuts like this one, which let you leverage one-line Python commands.

student () 
{
    # Discover the fully qualified program name. 
    path=`which docker 2>/dev/null`
    file=''
 
    # Parse the program name from the path.
    if [ -n ${path} ]; then
        file=${path##/*/}
    fi
 
    # Wrap when there is a file and it is rewrap.
    if [ -n ${file} ] && [[ ${file} = "docker" ]]; then
        python -c "import subprocess; subprocess.run(['docker exec -it --user student oracle23c bash'], shell=True)" 
    else
        echo "Docker is unavailable: Install the docker package."
    fi
}

Open a Ubuntu Terminal shell and type a student function name to connect to the Docker Oracle Database 23c Free instance where you can now test things like external tables with the SQL*Plus command line without installing it on the Ubuntu local operating system.

student@student-virtual-machine:~$ student
[student@d28375f0c43f ~]$ sqlplus c##student/student@free
 
SQL*Plus: Release 23.0.0.0.0 - Production on Wed Jan 3 02:14:22 2024
Version 23.3.0.23.09
 
Copyright (c) 1982, 2023, Oracle.  All rights reserved.
 
Last Successful login time: Wed Jan 03 2024 01:56:44 +00:00
 
Connected to:
Oracle Database 23c Free Release 23.0.0.0.0 - Develop, Learn, and Run for Free
Version 23.3.0.23.09
 
SQL>

Then, I added this sqlplus function to the /home/student/.bashrc file, which is owned by the student user. However, I also added the instruction to change to the student user’s home directory because the Oracle 23c Free container will connect you to the /home/oracle directory by default. I also added the default long list (ll) alias to the .bashrc file.

sqlplus () 
{
    # Discover the fully qualified program name. 
    path=`which rlwrap 2>/dev/null`
    file=''
 
    # Parse the program name from the path.
    if [ -n ${path} ]; then
        file=${path##/*/}
    fi;
 
    # Wrap when there is a file and it is rewrap.
    if [ -n ${file} ] && [[ ${file} = "rlwrap" ]]; then
        rlwrap sqlplus "${@}"
    else
        echo "Command-line history unavailable: Install the rlwrap package."
        $ORACLE_HOME/bin/sqlplus "${@}"
    fi
}
 
# Change to the user's home directory.
cd ${HOME}
 
# Create a long list alias:
alias ll='ls -l --color=auto'

After you’ve configured your student user, you can configure the oracle user account to work like a regular server. Exit the Docker Oracle Database 23c Free as the student user, then connect as the root user with this command:

docker exec -it -u root oracle23c bash

As the root user you can become the oracle user with the following command:

su - oracle

Now, add the following .bashrc shell in the /home/oracle directory:

# The oracle user's .bashrc
 
# Source global definitions
if [ -f /etc/bashrc ]; then
	. /etc/bashrc
fi
 
# User specific environment
if ! [[ "$PATH" =~ "$HOME/.local/bin:$HOME/bin:" ]]
then
    PATH="$HOME/.local/bin:$HOME/bin:$PATH"
fi
export PATH
 
# Uncomment the following line if you don't like systemctl's auto-paging feature:
# export SYSTEMD_PAGER=
 
# User specific aliases and functions
export ORACLE_SID=FREE
export ORACLE_BASE=/opt/oracle
export ORACLE_HOME=/opt/oracle/product/23c/dbhomeFree
export PATH=$PATH:/$ORACLE_HOME/bin
 
# Change to the user's home directory.
cd ${HOME}
 
# Create a long list alias:
alias ll='ls -l --color=auto'
 
sqlplus () 
{
    # Discover the fully qualified program name. 
    path=`which rlwrap 2>/dev/null`
    file=''
 
    # Parse the program name from the path.
    if [ -n ${path} ]; then
        file=${path##/*/}
    fi;
 
    # Wrap when there is a file and it is rewrap.
    if [ -n ${file} ] && [[ ${file} = "rlwrap" ]]; then
        rlwrap sqlplus "${@}"
    else
        echo "Command-line history unavailable: Install the rlwrap package."
        $ORACLE_HOME/bin/sqlplus "${@}"
    fi
}

You need to manually source the .bashrc for the oracle user because it’s not an externally available user. Use this syntax to connect as the internal user:

sqlplus / as sysdba

It’ll display:

SQL*Plus: RELEASE 23.0.0.0.0 - Production ON Wed Jan 3 07:08:11 2024
Version 23.3.0.23.09
 
Copyright (c) 1982, 2023, Oracle.  ALL rights reserved.
 
 
Connected TO:
Oracle DATABASE 23c Free RELEASE 23.0.0.0.0 - Develop, Learn, AND Run FOR Free
Version 23.3.0.23.09
 
SQL>

After all this, I can now click the “up arrow” to edit any of the sqlplus command history. If you like to work inside sqlplus natively, this should help you.

Written by maclochlainn

December 20th, 2023 at 11:11 pm

Ubuntu DaaS VM

without comments

Completed the build of my new Ubuntu Virtual Machine (VM) with Oracle 23c installed in a Docker instance, and MySQL and PostgreSQL installed locally. The VM image also provides a LAMP stack with Apache2, PHP 8.1 with MySQLi and PDO modules. Since the original post, I’ve added a number of items to support our program courses and the Data Science degrees.

There are lots of tricks and techniques in the blog associated with creating the build. I took the background photograph of Chapel Bridge early on Sunday morning August 30, 1987 in Lucerne Switzerland (with a Canon A1 and ASA 64 slide film that subsequently digitized well).

Next step: roll it out into an AWS image for the students to use for their courses.

Related blog posts:

As always, I hope the post and information helps others.

Written by maclochlainn

December 13th, 2023 at 1:15 am

Apache2 on Ubuntu

without comments

It’s always interesting when I build new instances. Ubuntu 22.0.4 was no different but I ran into an issue with installing Apache2 and eventually loading the mysqli module.

The Apache2 error was an issue with an unsupported module or hidden prerequisite. The MySQLi required an Apache reload after installation. Contrary to some erroneous posts the mysqli driver is supported on PHP 8.1.

Apache2 installation starts first and the mysqli module reload and verification script follows. On Ubuntu, you install Apache2 if you’re unaware of the hidden pre-requisite, otherwise install the pre-requisite first and avoid the error.

This is the command to install the apache2 module:

sudo apt-get install -y apache2

It generated the following error message:

apache2: Syntax error on line 146 of /etc/apache2/apache2.conf: Syntax error on line 1 of /etc/apache2/mods-enabled/wsgi.load: Cannot load /usr/lib/apache2/modules/mod_wsgi.so into server: /usr/lib/apache2/modules/mod_wsgi.so: cannot open shared object file: No such file or directory
Action 'start' failed.
The Apache error log may have more information.

Line 146 in the /etc/apache2/apache2.conf file contains the instruction to load modules. The error says it can’t find the mod_wsgi.so library, which was originally part of the deprecated Python 2.7 release.

IncludeOptional mods-enabled/*.load

The first step I pursued was finding the missing library, which appeared to be in the libapache2-mod-wsgi package. However, it became clear there is no installation candidate for that module, which supported Python 3.x. A little more research led me to find the appropriate library version for Python 3, which is found in the libapache2-mod-wsgi-py3 package.

I installed the libapache2-mod-wsgi-py3 package with the following syntax:

sudo apt-get install -y libapache2-mod-wsgi-py3

After applying it, I was able to start Apache2. Then, typing in localhost returns the Apache2 index.htm page, like:

After creating the following file in the default directory:

<?php
  phpinfo();
?>

Typing in localhost/infophp returns the Apache2 info.php page, like:

After the basics for PHP, the next step is the mysqli module for the MySQL database. This can be done in two steps on Ubuntu.

  1. Install the MySQLi software with the following syntax on Ubuntu:

    sudo apt-get install -y php8.1-mysql

    If you forget and use the old php-mysqli, it will redirect to the new PHP 8.1 MySQL module.

  2. You need to reload the Apache configuration with the following syntax:

    sudo systemctl reload apache2

Now, you can use the following PHP program to verify that the mysqli and pdo drivers are installed:

<html>
<header>
<title>Module Verification</title>
</header>
<body>
<?php
  if (!function_exists('mysqli_init') && !extension_loaded('mysqli')) {
    print 'mysqli not installed.'; }
  else {
    print 'mysqli installed.'; }
  if (!function_exists('pdo_init') && !extension_loaded('pdo')) {
    print '<p>pdo not installed.</p>'; }
  else {
    print '<p>pdo installed.</p>'; }
?>
</script>
</body>
</html>

If everything is correct, it should return the following in a browser when you query it from localhost/the-file-name and the file is in the /var/www/html directory:

mysqli installed.
 
pdo installed.

This means you can now write PHP applications, like the following example for my students:

I also have some demonstration programs that upload PNG files. As usual, I forgot about that while building the Ubuntu installation with MySQL 8, PHP 8.1 and Apache2. Fortunately, I solved it back in the day when moving from PHP 5.7 to 7.1 and here are the equivalent steps for Ubuntu:

I installed the libapache2-mod-wsgi-py3 package with the following syntax:

sudo apt-get install -y php-gd

Then, I restarted the Apache2 server to incorporate the php-gd library in my PHP module with this syntax:

sudo systemctl restart apache2.service

Retesting the PHP form to upload and render a PNG image file with this code (note that the only thing you can display is the html header and converted image, as shown on lines 64 and 65):

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
<?php
  /*  ConvertBlobToImage.php
   *  by Michael McLaughlin
   *
   *  This script queries an image from a BLOB column and
   *  converts it to a PNG image.
   *
   *  ALERT:
   *
   *  The header must be inside the PHP script tag because nothing
   *  can be rendered before the header() function call that signals
   *  this is a PNG file.
   */
 
    // Database credentials must be set manually because an include_once() function
    // call puts something ahead of the header, which causes a failure when rendering
    // an image.
 
    // Include the credential library.
    include_once("MySQLCredentials.inc");
 
  // Return successful attempt to connect to the database.
  if (!$c = @mysqli_connect(HOSTNAME,USERNAME,PASSWORD,DATABASE)) {
 
    // Print user message.
    print "Sorry! The connection to the database failed. Please try again later.";
 
    // Assign the OCI error and format double and single quotes.
    print mysqli_error();
 
    // Kill the resource.
    die();
  }
  else {
 
    // Declare input variables.
    $id = (isset($_GET['id'])) ? (int) $_GET['id'] : 1023;
 
    // Initialize a statement in the scope of the connection.
    $stmt = mysqli_stmt_init($c);
 
    // Declare a SQL SELECT statement returning a MediumBLOB.
    $sql = "SELECT item_blob FROM item WHERE item_id = ?";
 
    // Prepare statement and link it to a connection.
    if (mysqli_stmt_prepare($stmt,$sql)) {
      mysqli_stmt_bind_param($stmt,"i",$id);
 
      // Execute the PL/SQL statement.
      if (mysqli_stmt_execute($stmt)) {
 
        // Bind result to local variable.
	      mysqli_stmt_bind_result($stmt, $image);
 
        // Read result.
        mysqli_stmt_fetch($stmt);
      }
    } 
 
    // Disconnect from database.
    mysqli_close($c);
 
    // Print the header first.
    header('Content-type: image/png');
    imagepng(imagecreatefromstring($image));
  }
?>

The call to the ConvertMySQLBlobToImage.php is handled in an image tag, as shown:

<img src="ConvertMySQLBlobToImage.php?id='.$id.'">

Rendering a web page, like:

As always, I hope this explains something worthwhile.

Written by maclochlainn

December 10th, 2023 at 11:25 pm

OracleDB Python Tutorial 1

without comments

This shows you how to get Python working with the Oracle Database 23c in Docker or Podman on Ubuntu. You can find useful connection strings for this in Oracle Database Free Get Started.

  1. First step requires you to install the pip3/span> utility on Ubuntu.

    sudo apt install -y python3-pip

  2. Second step requires that you pip3 install the oracledb library:

    sudo pip3 install oracledb --upgrade

  3. Third step requires you write a Python program to test your connection to Oracle Database 23c Free, like:

    1
    2
    3
    4
    5
    6
    7
    8
    9
    10
    11
    12
    13
    14
    15
    16
    17
    18
    19
    20
    
    #!/usr/bin/python
     
    # Import the Oracle library.
    import oracledb
     
    try:
      # Create a connection to local Docker or Podman installation.
      db = oracledb.connect(user='c##student', password='student', dsn='localhost:51521/FREE')
     
      # Print a connection message.
      print("Connected to the Oracle", db.version, "database.")
     
    except oracledb.DatabaseError as e:
      error, = e.args
      print(sys.stderr, "Oracle-Error-Code:", error.code)
      print(sys.stderr, "Oracle-Error-Message:", error.message)
     
    finally:
      # Close connection. 
      db.close()

    The 51521 port is the recommended port when setting up Docker or Podman services, however, it can be set to any port above 1024.

    It should print:

    Connected to the Oracle 23.3.0.23.9 database.
  4. Fourth step requires you write a Python program to test querying data from an Oracle Database 23c Free instance. I created the following avenger table and seeded it with six Avengers.

    1
    2
    3
    4
    5
    6
    7
    8
    9
    10
    11
    12
    13
    14
    15
    16
    17
    
    /* Conditionally drop the table. */
    DROP TABLE IF EXISTS avenger;
     
    /* Create the table. */
    CREATE TABLE avenger
    ( avenger_id      NUMBER
    , first_name      VARCHAR2(20)
    , last_name       VARCHAR2(20)
    , character_name  VARCHAR2(20));
     
    /* Seed the table with data. */
    INSERT INTO avenger VALUES (1,'Anthony','Stark','Iron Man');
    INSERT INTO avenger VALUES (2,'Thor','Odinson','God of Thunder');
    INSERT INTO avenger VALUES (3,'Steven','Rogers','Captain America');
    INSERT INTO avenger VALUES (4,'Bruce','Banner','Hulk');
    INSERT INTO avenger VALUES (5,'Clinton','Barton','Hawkeye');
    INSERT INTO avenger VALUES (6,'Natasha','Romanoff','Black Widow');

    Then, I extended the program logic to include a cursor and for loop to read the values from the avenger table:

    1
    2
    3
    4
    5
    6
    7
    8
    9
    10
    11
    12
    13
    14
    15
    16
    17
    18
    19
    20
    21
    22
    23
    24
    25
    26
    27
    28
    29
    30
    31
    32
    
    #!/usr/bin/python
     
    # Import the Oracle library.
    import oracledb
     
    try:
      # Create a connection to local Docker or Podman installation.
      db = oracledb.connect(user='c##student', password='student', dsn='localhost:51521/FREE')
     
      # Create a cursor.
      cursor = db.cursor()
     
      # Execute a query.
      cursor.execute("SELECT   character_name " +
                     ",        first_name " +
                     ",        last_name " +
                     "FROM     avenger " +
                     "ORDER BY character_name")
     
      # Read the contents of the cursor.
      for row in cursor:
        print(row[0] + ':',row[2] + ',',row[1])
     
    except oracledb.DatabaseError as e:
      error, = e.args
      print(sys.stderr, "Oracle-Error-Code:", error.code)
      print(sys.stderr, "Oracle-Error-Message:", error.message)
     
    finally:
      # Close cursor and connection.
      cursor.close() 
      db.close()

    The 51521 port is the recommended port when setting up Docker or Podman services, however, it can be set to any port above 1024.

    It should print:

    Black Widow: Romanoff, Natasha
    Captain America: Rogers, Steven
    God of Thunder: Odinson, Thor
    Hawkeye: Barton, Clinton
    Hulk: Banner, Bruce
    Iron Man: Stark, Anthony
  5. Fifth step requires you write a Python program to test querying data filtered by a local variable from an Oracle Database 23c Free instance. This example looks only for the Hulk among the six Avengers.

    1
    2
    3
    4
    5
    6
    7
    8
    9
    10
    11
    12
    13
    14
    15
    16
    17
    18
    19
    20
    21
    22
    23
    24
    25
    26
    27
    28
    29
    30
    31
    32
    33
    34
    35
    36
    
    #!/usr/bin/python
     
    # Import the Oracle library.
    import oracledb
     
    try:
      # Create a connection to local Docker or Podman installation.
      db = oracledb.connect(user='c##student', password='student', dsn='localhost:51521/FREE')
     
      # Create a cursor.
      cursor = db.cursor()
     
      # Execute a query.
      stmt = "SELECT   character_name "            \
             ",        first_name "                \
             ",        last_name "                 \
             "FROM     avenger "                   \
             "WHERE    character_name = :avenger " \
             "ORDER BY character_name"
     
      # Execute with bind variable.
      cursor.execute(stmt, avenger = "Hulk")
     
      # Read the contents of the cursor.
      for row in cursor:
        print(row[0] + ':',row[2] + ',',row[1])
     
    except oracledb.DatabaseError as e:
      error, = e.args
      print(sys.stderr, "Oracle-Error-Code:", error.code)
      print(sys.stderr, "Oracle-Error-Message:", error.message)
     
    finally:
      # Close cursor and connection. 
      cursor.close() 
      db.close()

    It should print:

    Hulk: Banner, Bruce

As always, I hope this puts everything together for setting up Python with Oracle Database 23c Free.

Written by maclochlainn

December 10th, 2023 at 12:27 am

pgAdmin4 on Ubuntu

without comments

Installing pgAdmin4 is qualified by the pgAdmin4 (APT) web page, which relies on the curl utility. Ubuntu doesn’t install curl by default, so you need to install it before you can download and install pgAdmin4:

  1. Download and install curl utility

    sudo apt-get install -y curl

  2. Download and install the public key for the repository (if not done previously):

    sudo curl -fsS https://www.pgadmin.org/static/packages_pgadmin_org.pub | sudo gpg --dearmor -o /usr/share/keyrings/packages-pgadmin-org.gpg

    It may find an existing key and require you to confirm its replacement:

    File '/usr/share/keyrings/packages-pgadmin-org.gpg' exists. Overwrite? (y/N) y
  3. Create the repository configuration file:

    sudo sh -c 'echo "deb [signed-by=/usr/share/keyrings/packages-pgadmin-org.gpg] https://ftp.postgresql.org/pub/pgadmin/pgadmin4/apt/$(lsb_release -cs) pgadmin4 main" > /etc/apt/sources.list.d/pgadmin4.list && apt update'

  4. Install the pgadmin4 Desktop:

    sudo apt install pgadmin4-desktop

  5. You can launch your pgadmin4 program file or by clicking the pgAdmin4 icon in the other applications menu:

  6. It takes a couple moments to launch the pgadmin4 desktop. The initial screen will look like:

  7. After pgadmin4 launches, you’re prompted for a master password. Enter the password and click the OK button to proceed or simply let it sit for a couple minutes to avoid entering a password.

  8. After entering the password or skipping its entry you arrive at the base dialog, as shown.

  9. Click the Add New Server link, which prompts you to register your database. Enter videodb in the Name field and click the Connection tab to the right of the General tab.

  10. In the Connection dialog, enter the following values:

    • Host name/address: localhost
    • Port: 5432
    • Maintenance database: postgres
    • Username: student
    • Password: student

    Enter a name for your database. In this example, videodb is the Server Name. Click the Save button to proceed.

  11. Having completed the configuration, you now see the home page.

This completes the instructions for installing, configuring, and using PostgreSQL on AlmaLinux. As always, I hope it helps those looking for instructions.

Written by maclochlainn

December 7th, 2023 at 10:36 pm

Posted in Linux,Ubuntu

Oracle 23c MLE JavaScript

without comments

Oracle Database 23c has some really great features. One of those features is the ability to write JavaScript functions inside the database. Unfortunately, I noticed a couple omissions in Oracle’s JavaScript Developer’s Guide. Specifically, I encountered a privilege error while testing the example in the 5.1 Call Specifications for Functions example.

After having typed it all in to a simple script file, I encountered the following error message when trying to create an MLE MODULE:

CREATE OR REPLACE MLE MODULE jsmodule
*
ERROR AT line 1:
ORA-01031: insufficient PRIVILEGES
Help: https://docs.oracle.com/error-help/db/ora-06575

That was easy enough to fix. As the system user you need to grant the following two additional privileges to the user (based on my earlier sandbox pluggable user configuration user setup), which in my case is the c##student pluggable user:

GRANT CREATE MLE TO c##student;
GRANT EXECUTE ON JAVASCRIPT TO c##student;

You need to enable the SQL*PLus SERVEROUTPUT environment parameter for Oracle’s code example to work when you run the greet procedure from SQL*Plus command-line interface (CLI).

Below is the modified example file (unfortunately, the GeSHi formatting promotes log and return in the JavaScript functions to uppercase because they’re assumed as keywords in Oracle SQL):

  1. Conditionally drop the MLE MODULE.

    DROP MLE MODULE IF EXISTS jsmodule;
  2. Create a MLE Call Specification.

    1
    2
    3
    4
    5
    6
    7
    8
    9
    10
    11
    12
    
    CREATE OR REPLACE
      MLE MODULE jsmodule
      LANGUAGE JAVASCRIPT AS
     
      export function greet(str) {
        console.log(`Hello ${str}!`)
      }
     
      export function concat(str1, str2) {
        return str1 + " " + str2 + "!";
      }
    /
  3. The greet function doesn’t return a value and uses the Nodejs console.log() function to write a string, which means you must wrap the JavaScript function as a procedure because it returns a void type.

    1
    2
    3
    4
    5
    
    CREATE OR REPLACE
      PROCEDURE greet(str in VARCHAR2)
      AS MLE MODULE jsmodule
      SIGNATURE 'greet(string)';
    /
  4. Wrap the concatenate function as a function because it returns a value inside the JavaScript.

    1
    2
    3
    4
    5
    6
    7
    
    CREATE OR REPLACE
      FUNCTION concatenate
      ( str1  VARCHAR2
      , str2  VARCHAR2 ) RETURN VARCHAR2 AS
      MLE MODULE jsmodule
      SIGNATURE 'concat(string, string)';
    /
  5. Enable to the SERVEROUTPUT environment variable to display messages printed from inside stored procedures or other PL/SQL blocks.

    SET SERVEROUTPUT ON SIZE UNLIMITED
  6. Call the greet(literal|variable) function’s procedure wrapper.

    CALL greet('Peter');

    It returns

    Hello Peter!
    

  7. Query the result from the concatenate() function’s function wrapper. */

    SELECT concatenate('Hello','World');

    It returns

    Hello World!
    

As always, I hope this helps somebody working through the same issue.

Written by maclochlainn

December 5th, 2023 at 12:41 am

Python3 on PostgreSQL

without comments

The necessary Python 3 driver for connections to the PostgreSQL database is python3-psycopg2, as qualified by this earlier post with full test examples for Red Hat distributions. You can install it on Ubuntu with the following command:

sudo apt-get install -y python3-psycopg2

As always, I hope this helps those looking for a solution. Also, remember the referenced post above provides Linux distribution neutral full solutions.

Written by maclochlainn

December 3rd, 2023 at 11:00 pm

SQL Developer on Ubuntu

without comments

The following steps show how to install and configure SQL Developer on Ubuntu 22.0.4 to work with Oracle Database 23c Free in a Docker container. The first steps are installing the Java Runtime Environment and Java Development Kit, and then downloading, installing and configuring SQL Developer. These are the required steps:

  1. Install the Java Runtime Environment:

    sudo apt install default-jre

    The log file for this is:

  2. Install the Java Runtime Environment:

    sudo apt install -y default-idk

    The log file for this is:

  3. Download SQL Developer from here; and then install SQL Developer to the /opt directory on your Ubuntu local instance:

    Use the following command to unzip the SQL Developer files to the /opt directory:

    sudo unzip ~/Downloads/sqldeveloper-23.1.0.097.1607-no-jre.zip
  4. Create the following /usr/local/bin/sqldeveloper symbolic link:

    sudo ln -s /opt/sqldeveloper/sqldeveloper.sh /usr/local/bin/sqldeveloper
  5. Edit the /opt/sqldeveloper/sqldeveloper.sh file by replacing the following line:

    cd "`dirname $0`"/sqldeveloper/bin && bash sqldeveloper $*

    with this version:

    /opt/sqldeveloper/sqldeveloper/bin/sqldeveloper $*
  6. Now, you can launch SQL Developer from any location on your local Ubuntu operating system, like:

    sqldeveloper
  7. You can now connect as the system user through SQL Developer to the Oracle Database 23c Free Docker instance with the following connection information:

  8. You can also create a Desktop shortcut by creating the sqldeveloper.desktop file in the /usr/share/applications directory. The SQL Developer icon is provided in the sqldeveloper base directory.

    You should create the following sqldeveloper.desktop file to use a Desktop shortcut:

    [Desktop Entry]
    Name=Oracle SQL Developer
    Comment=SQL Developer from Oracle
    GenericName=SQL Tool
    Exec=/usr/local/bin/sqldeveloper
    Icon=/opt/sqldeveloper/icon.png
    Type=Application
    StartupNotify=true
    Categories=Utility;Oracle;Development;SQL;

You can create a sandboxed container c##student user with the instructions from this earlier post on Oracle Database 18c, which remains the correct syntax.

As always, I hope this helps those trying to accomplish this task.

Written by maclochlainn

December 3rd, 2023 at 12:11 am

Disk Space Allocation

without comments

It’s necessary to check for adequate disk space on your Virtual Machine (VM) before installing Oracle 23c Free in a Docker container or as a podman service. Either way, it requires about 13 GB of disk space. On Ubuntu, the typical install of a VM allocates 20 GB and a 500 MB swap. You need to create a 2 GB swap when you install Ubuntu or plan to change the swap, as qualified in this excellent DigitalOcean article. Assuming you installed it with the correct swap or extended your swap area, you can confirm it with the following command:

sudo swapon --show

It should return something like this:

NAME      TYPE SIZE USED PRIO
/swapfile file 2.1G 1.2G   -2

Next, check your disk space allocation and availability with this command:

df -h

This is what was in my instance with MySQL and PostgreSQL databases already installed and configured with sandboxed schemas:

Filesystem      Size  Used Avail Use% Mounted on
tmpfs           388M  2.1M  386M   1% /run
/dev/sda3        20G   14G  4.6G  75% /
tmpfs           1.9G   28K  1.9G   1% /dev/shm
tmpfs           5.0M  4.0K  5.0M   1% /run/lock
/dev/sda2       512M  6.1M  506M   2% /boot/efi
tmpfs           388M  108K  388M   1% /run/user/1000

Using VMware Fusion on my Mac (Intel-based i9), I changed the allocated space from 20 GB to 40 GB by navigating to Virtual Machine, Settings…, Hard Disk. I entered 40.00 as the disk size and clicked the Pre-allocate disk space checkbox before clicking the Apply button, as shown in below. This added space is necessary because Oracle Database 23c Free as a Docker instance requires almost 10 GB of local space.

After clicking the Apply button, I checked Ubuntu with the “df -h” command and found there was no change. That’s unlike doing the same thing on AlmaLinux or a RedHat distribution, which was surprising.

The next set of steps required that I manually add the space to the Ubuntu instance:

  1. Start the Ubuntu VM and check the instance’s disk information with fdisk:

    sudo fdisk -l

    The log file for this is:

    After running fdisk, I rechecked disk allocation with df -h and saw no change:

    Filesystem      Size  Used Avail Use% Mounted on
    tmpfs           388M  2.1M  386M   1% /run
    /dev/sda3        20G   14G  4.6G  75% /
    tmpfs           1.9G   28K  1.9G   1% /dev/shm
    tmpfs           5.0M  4.0K  5.0M   1% /run/lock
    /dev/sda2       512M  6.1M  506M   2% /boot/efi
    tmpfs           388M  108K  388M   1% /run/user/1000
  2. So, I installed Ubuntu’s user space utility gparted:

    sudo apt install gparted

    The log file for this is:

  3. After installing the gparted utility (manual can be found here), you can launch it with the following syntax:

    sudo gparted

    You’ll see the following in the console, which you can ignore.

    GParted 1.3.1
    configuration --enable-libparted-dmraid --enable-online-resize
    libparted 3.4

    It launches a GUI interface that should look something like the following:

    Right-click on the /dev/sda3 Partition and the GParted application will present the following context popup menu. Click the Resize/Move menu option.

    The attempt to resize the disk at this point GParted will raise a read-only exception like the following:

    You might open a new shell and fix the disk at the command-line but you’ll need to relaunch gparted regardless. So, you should close gparted and run the following commands:

    sudo mount -o remount -rw /
    sudo mount -o remount -rw /var/snap/firefox/common/host-hunspell

    When you relaunch GParted, you see that the graphic depiction has changed when you right-click on the /dev/sda3 Partition as follows:

    Click on the highlighted box with the arrow and drag it all the way to the right. It will then show you something like the following.

    Click the Resize button to make the change and add the space to the Ubuntu file system and see something like the following in Gparted:

    Choose Edit in the menu bar and then Apply All Operations to effect the change in the disk allocation. The last dialog will require you to verify you want to make the changes. Click the Apply button to make the changes.

    Click the close for the GParted application and then you can rerun the following command:

    df -h

    You will see that you now have 19.5 GB of additional space:

    Filesystem      Size  Used Avail Use% Mounted on
    tmpfs           388M  2.2M  386M   1% /run
    /dev/sda3        39G 19.5G   23G  39% /
    tmpfs           1.9G   28K  1.9G   1% /dev/shm
    tmpfs           5.0M  4.0K  5.0M   1% /run/lock
    /dev/sda2       512M  6.1M  506M   2% /boot/efi
    tmpfs           388M  116K  388M   1% /run/user/1000
  4. Finally, you can now successfully download the latest Docker version of Oracle Database 23c Free with the following command:

    docker run --name oracle23c -p 1521:1521 -p 5500:5500 -e ORACLE_PWD=cangetin container-registry.oracle.com/database/free:latest

    Since you haven’t downloaded the container, you’ll get a warning that it is unable to find the image before it discovers it and downloads it. This will take several minutes. At the conclusion, it will start the Oracle Database Net Listener and begin updating files. the updates may take quite a while to complete.

    The basic download console output looks like the following and if you check your disk space you’ve downloaded about 14 GB in the completed container.

    Unable to find image 'container-registry.oracle.com/database/free:latest' locally
    latest: Pulling from database/free
    089fdfcd47b7: Pull complete 
    43c899d88edc: Pull complete 
    47aa6f1886a1: Pull complete 
    f8d07bb55995: Pull complete 
    c31c8c658c1e: Pull complete 
    b7d28faa08b4: Pull complete 
    1d0d5c628f6f: Pull complete 
    db82a695dad3: Pull complete 
    25a185515793: Pull complete 
    Digest: sha256:5ac0efa9896962f6e0e91c54e23c03ae8f140cf6ed43ca09ef4354268a942882
    Status: Downloaded newer image for container-registry.oracle.com/database/free:latest

    My detailed log file for the complete recovery operation is:

  5. You can connect to the Oracle Database 23c Free container with the following syntax:

    docker exec -it -u root oracle23c bash

    At the command-line, you connect to the Oracle Database 23c Free container with the following syntax:

    sqlplus system/cangetin@free

    You have arrived at the Oracle SQL prompt:

    SQL*Plus: Release 23.0.0.0.0 - Production on Fri Dec 1 00:13:55 2023
    Version 23.3.0.23.09
     
    Copyright (c) 1982, 2023, Oracle.  All rights reserved.
     
    Last Successful login time: Thu Nov 30 2023 23:27:54 +00:00
     
    Connected to:
    Oracle Database 23c Free Release 23.0.0.0.0 - Develop, Learn, and Run for Free
    Version 23.3.0.23.09
     
    SQL>

As always, I hope this helps those trying to work with the newest Oracle stack.

Written by maclochlainn

December 1st, 2023 at 3:08 pm