DapperLib
DynamicParameters DbType Mapping Issues in Parameterized Queries
Parameter Type Mapping Precision Issue in Dapper Parameterized Queries When using Dapper for parameterized queries, automatically inferred database parameter types based on the parameter value's DbType may lack precision. For example:
DbType.AnsiString is mapped to NpgsqlDbType.Text in PostgreSQL/Npgsql. This imprecise mapping can lead to inefficient query execution plans, resulting in prolonged query times and degraded performance (e.g., due to implicit type conversions or index mismatches).
Proposed Solution To address this, we recommend extending Dapper to allow explicit configuration of parameter types before SQL execution via DbCommand. This could be achieved by:
Introducing an extensibility mechanism (e.g., injected extension objects) to override parameter mappings where necessary. Enforcing precise database-specific types (e.g., NpgsqlDbType.Citext, NpgsqlDbType.Jsonb) instead of relying on generic DbType defaults.
