Implicit Casts That Defeat an Index

Concepts covered: sqlCast

The first platform concern is codec alignment. Data leaves a source database in one type system, traverses a serialization format, lands in a storage layer, and is read by a consumer with its own type system. Each step's type system has to align with the next; misalignment is data loss. Type system mappings Postgres NUMERIC(20,4) maps to Avro {type: bytes, logicalType: decimal, precision: 20, scale: 4}. Iceberg's DECIMAL(20, 4) reads that Avro and stores it natively. Snowflake's NUMBER(20,4) reads from Iceberg via the connector. Arrow's Decimal128 with the same precision and scale reads from Snowflake for ML serving. Each step is one explicit mapping; the precision contract is preserved. State this when designing: 'the type mapping is explicit at every boundary; the platform documents the

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