How to pass array into parameters of function

When working with H2 Database, passing arrays as parameters to custom functions can sometimes throw confusing errors. If you’re encountering errors like Hexadecimal string contains non-hex character, this guide will help you resolve the issue.

Understanding the Problem

You want to create a custom function array_contains_all in H2 that checks if all elements of a sub-array exist in a source array. Here’s what you tried:

1. First Attempt: Declaring the arrays as java.util.HashSet.
   Error: H2 cannot handle arrays directly as HashSet from SQL.
2. Second Attempt: Using java.sql.Array and converting it to a List.
   Error: The same hexadecimal string error persists because H2 doesn’t properly interpret arrays in this context.

Solution: Correct Way to Pass and Process Arrays in H2

To correctly handle arrays in H2, you need to process them as simple Object[] directly in your custom function. Follow these steps:

Step 1: Create the Function Alias

Use the following SQL command to create the function alias:

CREATE ALIAS IF NOT EXISTS array_contains_all AS '
boolean arrayContainsAll(Object[] sourceArray, Object[] subArray) {
    // Convert arrays to Lists for easier manipulation
    java.util.List<Object> sourceArrayList = java.util.Arrays.asList(sourceArray);
    java.util.List<Object> subArrayList = java.util.Arrays.asList(subArray);
    // Check if sourceArray contains all elements of subArray
    return sourceArrayList.containsAll(subArrayList);
}';

Step 2: Call the Function

To call the function and pass the arrays as parameters, use the following SQL:

SELECT array_contains_all(
    ARRAY['HELLO', 'WORLD', 'FRIEND'],
    ARRAY['HELLO', 'WORLD']
) AS result;

Expected Output

If all elements in the second array exist in the first array, the result will be:

result
------
TRUE

Why Does This Work?

1. Use of Object[]: H2 internally processes arrays as Object[]. Using this simplifies array handling without requiring additional conversions.
2. java.util.Arrays.asList: Converts arrays to lists, enabling the use of .containsAll(), a straightforward way to check for inclusion.
3. No Need for java.sql.Array: Avoids unnecessary conversions that often lead to the Hexadecimal string error.

Common Pitfalls to Avoid

1. Using Non-Compatible Data Types: Always use Object[] instead of HashSet or java.sql.Array for array parameters in H2.
2. Incorrect SQL Syntax: Ensure you correctly pass arrays using the ARRAY[] syntax.
3. Data Type Mismatches: Make sure the arrays contain compatible data types (e.g., all strings or all integers).

Keywords:

• H2 Database custom function
• Pass arrays in H2
• H2 function alias example
• Array handling in H2 SQL
• Hexadecimal string error in H2

Meta Description:

Learn how to pass arrays as parameters in H2 Database function aliases. This guide resolves the “Hexadecimal string contains non-hex character” error with working examples.

By following this approach, you can seamlessly handle arrays in H2 Database without running into frustrating errors. Try it out and elevate your database operations!