SQL LIKE to Oracle NoSQL regex_like Converter

[dario-vega]

Overview

Oracle NoSQL Database does not support the standard SQL LIKE operator but instead uses regex_like() with a limited subset of regex features. This proposal introduces a Java utility to automatically convert SQL LIKE patterns to Oracle NoSQL-compatible regex_like() patterns.

Problem Statement

When migrating SQL queries to Oracle NoSQL or working with both SQL and NoSQL databases, developers must manually convert LIKE patterns to regex_like() patterns. This is error-prone and time-consuming due to:

1. Different wildcard syntax: SQL % and _ vs regex .* and .
2. Limited regex support: Oracle NoSQL only supports ., *, \\ escaping, and \\Q...\\E quoting
3. Special character handling: Literal characters like ., *, [, ] must be properly escaped or quoted

Proposed Solution

A Java converter utility that provides:

Core Features

1. Pattern Conversion: Converts SQL LIKE patterns to regex_like patterns

   • %Smith% → .*\\QSmith\\E.*
   • J_hn → \\QJ\\E.\\Qhn\\E
   • %.txt → .*\\Q.txt\\E

2. Two Quoting Styles:

   • QUOTE_BLOCKS: Uses \\Q...\\E for literal sections (default)
     • Example: %**Houston**% → .*\\Q**Houston**\\E.*
   • ESCAPE_INDIVIDUAL: Uses \\ to escape each special character
     • Example: %**Houston**% → .*\\*\\*Houston\\*\\*.*

3. WHERE Clause Conversion: Automatically converts entire WHERE clauses

   • Input: name LIKE '%Smith%'
   • Output: regex_like(name, '.*\\QSmith\\E.*')

4. Escaped Wildcard Support: Handles SQL escaped wildcards (\_, \%)

   • test\_user% → \\Qtest\\E\\Q_\\E\\Quser\\E.*

API Design

// Basic conversion (default QUOTE_BLOCKS style)
String regex = LikeToRegexConverter.convertLikeToRegex("%Smith%");

// Specify quoting style
String regex = LikeToRegexConverter.convertLikeToRegex(
    "%**Houston**%", 
    QuotingStyle.ESCAPE_INDIVIDUAL
);

// Convert entire WHERE clause
String sql = LikeToRegexConverter.convertWhereClause(
    "name LIKE '%Smith%' AND email NOT LIKE '%@temp.com'",
    QuotingStyle.QUOTE_BLOCKS
);

Conversion Rules

SQL Pattern	Oracle NoSQL regex_like	Notes
%	.*	Zero or more characters
_	.	Exactly one character
\%	\\Q%\\E or \\.\\*	Literal % character
\_	\\Q_\\E or \\.	Literal _ character
Literal text	\\Q...\\E	Quote special characters
. * [ ]	Escaped or quoted	Prevent regex interpretation

Implementation

The complete implementation is available as a single Java class with:

• Zero external dependencies
• Comprehensive test suite
• Pattern validation
• Side-by-side style comparison

Supported Oracle NoSQL regex_like Features

Oracle NoSQL regex_like supports only these metacharacters:

• . (period): matches any single character except newline
• * (asterisk): zero or more occurrences of preceding element
• \\ (double backslash): escape metacharacters (e.g., \\. or \\*)
• \\Q...\\E: quote literal strings (e.g., \\Q**Houston**\\E)

Unsupported Features

The following standard regex features are NOT supported in Oracle NoSQL:

• ❌ Character classes: [abc], [^abc], [a-z]
• ❌ Anchors: ^, $
• ❌ Quantifiers: +, ?, {n}, {n,m}
• ❌ Groups and alternation: (), |
• ❌ Case-insensitive flags: (?i)

Use Cases

1. Migration Tools: Automated SQL to NoSQL query conversion
2. Query Builders: Dynamic query generation supporting both SQL and NoSQL
3. Developer Tools: IDE plugins or CLI tools for query conversion
4. Documentation: Reference implementation for conversion rules

Testing

The implementation includes:

• Unit tests for common patterns
• Edge case handling (escaped wildcards, special characters)
• Pattern matching validation
• Both quoting styles produce equivalent results

Example Output

Basic Patterns

Input:  name LIKE '%Smith%'
Output: regex_like(name, '.*\\QSmith\\E.*')

Input:  filename LIKE '%.pdf'
Output: regex_like(filename, '.*\\Q.pdf\\E')

Input:  data LIKE '%**URGENT**%'
Output: regex_like(data, '.*\\Q**URGENT**\\E.*')

Comparison Table

LIKE Pattern	QUOTE_BLOCKS Style	ESCAPE_INDIVIDUAL Style
%Smith%	.*\\QSmith\\E.*	.*Smith.*
%.txt	.*\\Q.txt\\E	.*\\.txt
%**Houston**%	.*\\Q**Houston**\\E.*	.*\\*\\*Houston\\*\\*.*
J_hn	\\QJ\\E.\\Qhn\\E	J.hn
test\_user%	\\Qtest\\E\\Q_\\E\\Quser\\E.*	test\\.user.*

Complete Query Examples

-- Original SQL Query
SELECT * FROM users $t 
WHERE email LIKE '%@gmail.com'

-- Converted Query (QUOTE_BLOCKS)
SELECT  * FROM users $t 
WHERE regex_like(email, '.*\\Q@gmail.com\\E')

-- Converted Query (ESCAPE_INDIVIDUAL)
SELECT  * FROM users $t 
WHERE regex_like(email, '.*@gmail.com')

Benefits

• ✅ Reduces manual conversion errors
• ✅ Maintains query readability
• ✅ Supports both quoting styles
• ✅ Handles edge cases (escaped wildcards, special characters)
• ✅ Zero dependencies - single file utility
• ✅ Production-ready with comprehensive testing
• ✅ Respects Oracle NoSQL regex_like limitations

Code Availability

The complete Java implementation is available in this discussion. Key features:

• Class Name: LikeToRegexConverter
• Package: Standalone (no package dependency)
• Dependencies: None (uses only Java standard library)
• Java Version: Java 8+

Installation & Usage

As a Utility Class

1. Copy LikeToRegexConverter.java to your project
2. Import and use:

import LikeToRegexConverter;
import LikeToRegexConverter.QuotingStyle;

// Convert pattern
String regex = LikeToRegexConverter.convertLikeToRegex("%Smith%");

// Convert WHERE clause
String query = "SELECT * FROM users $t WHERE name LIKE '%John%'";
String converted = LikeToRegexConverter.convertWhereClause(query);

Running the Demo

javac LikeToRegexConverter.java
java LikeToRegexConverter

The demo will show:

• Side-by-side comparison of both quoting styles
• Pattern matching validation
• Complete query examples
• Conversion rules reference

Performance Considerations

• Time Complexity: O(n) where n is the pattern length
• Space Complexity: O(n) for the output string
• Thread Safety: All methods are stateless and thread-safe
• Bulk Conversion: Efficient for processing multiple patterns

Discussion

I'd love to hear feedback on:

• Use cases: Where would you use this converter?
• Features: What additional features would be helpful?
• Performance: Any specific performance requirements?
• Integration: How would you like to integrate this (library, plugin, CLI)?
• Quoting style: Which style do you prefer (QUOTE_BLOCKS vs ESCAPE_INDIVIDUAL)?

Please share your thoughts, suggestions, and use cases!

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Related Resources

• Oracle NoSQL Database Documentation
• Oracle NoSQL SQL Reference

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Tags: oracle-nosql sql regex query-conversion migration java