Pattern Matching

What is Pattern Matching?

Pattern matching locates strings that conform to a defined pattern: wildcards (*, ?), regular expressions (regex), or domain-specific grammars. It’s used in search pipelines, validation, extraction, and analytics—not as a replacement for ranking.

How It Works (quick)

• Wildcards: Simple glob matching for prefixes/suffixes (nike*, -270).
• Regex: Rich operators (character classes, groups, quantifiers, anchors) for precise capture.
• Engines: Run on tokens, raw text, or logs; apply boundaries and flags (case/diacritics).
• Outputs: Booleans (match/no match) or captured groups (e.g., SKU, MPN, GTIN).

Why It Matters in E-commerce

• Validation: Enforce SKU/MPN formats on ingest.
• Extraction: Pull model numbers, sizes, or order IDs from titles, reviews, and emails.
• Routing: Detect navigational queries for best bets or redirects.
• QA/analytics: Spot bad titles, duplicate patterns, or spam.

Best Practices

• Anchor & bound: Use ^/$, word boundaries, and length caps to avoid over-matching.
• Pre-normalize: Fold case/diacritics and whitespace before matching.
• Performance: Avoid catastrophic backtracking; precompile regex; sample on large logs.
• Security: Sanitize user-provided patterns; set timeouts; block ReDoS.
• Governance: Version patterns; add tests and golden examples.

Challenges

• Multilingual quirks, ambiguous formats, noisy vendor copy, and brittle over-specific patterns.

Examples

• SKU validation: ^[A-Z]{2}-\\\\d{4}(-[A-Z0-9]{1,3})?$
• Size capture: \\\\b(EU|US)\\\\s?(\\\\d{2}(\\\\.5)?)\\\\b
• Query routing: detect ^sku:\\\\S+$ or ^order\\\\s?#?\\\\d+.

Summary

Pattern matching is a precision tool for validation and extraction. Anchor patterns, normalize inputs, and guard performance/security to keep pipelines fast and safe.