Add selectExpression for transforming primary keys.

[IgorOleksyuk]

Add a support for data transformation during migration using various hash functions. This feature is useful for:

• Data anonymization: Hash sensitive data like emails, phone numbers, or personal identifiers
• Data obfuscation: Transform data while maintaining referential integrity
• Compliance requirements: Meet data privacy regulations by hashing PII data

We need supported Hash Functions:

• MurmurHash3: Fast, non-cryptographic hash function (returns integer)
• MD5: 128-bit cryptographic hash (returns hex string)
• SHA-1: 160-bit cryptographic hash (returns hex string)
• SHA-256: 256-bit cryptographic hash (returns hex string)
• XXHASH64: Fast, 64-bit non-cryptographic hash (returns long integer)

Transform Expression Parameters

• columnName: The source column to transform to hash value
• rule: Hash function to apply (murmurhash3, md5, sha-1, sha-256, xxhash64)
• alias: Optional new column name (if not provided, replaces original column)
• keepSource: Boolean to keep original column when using alias (default: false)

--json-mapping '{ "keyspaces": { "transformation": { "enabled": true, "transformExpressions": [ { "columnName": "email", "rule": "md5", "alias": "email_hash", "keepSource": false }, { "columnName": "phone", "rule": "sha-256", "alias": "phone_hash", "keepSource": true }, { "columnName": "user_id", "rule": "murmurhash3" } ] } } }'

[nwheeler81]

@IgorOleksyuk ready to test. Please use the code from this branch 197-add-selectexpression-for-transforming-primary-keys.

[nwheeler81]

@IgorOleksyuk any update? is it working for you?