Glossary

This glossary defines codebase-specific terms, jargon, and domain concepts used within the Npgsql Entity Framework Core provider.

EF Core Provider Concepts

Type Mapping

The system responsible for bridging .NET CLR types and PostgreSQL database types.

• NpgsqlTypeMappingSource: The central discovery point for type mappings. It resolves mappings based on CLR types, store type names (SQL), or model metadata src/EFCore.PG/Storage/Internal/NpgsqlTypeMappingSource.cs23-24
• RelationalTypeMapping: An EF Core base class that Npgsql extends to handle specific PostgreSQL types like jsonb, inet, or uuid src/EFCore.PG/Storage/Internal/NpgsqlTypeMappingSource.cs67-124

SQL Generation

The process of turning an EF Core SelectExpression or MigrationOperation into a PostgreSQL-compatible SQL string.

• NpgsqlQuerySqlGenerator: Responsible for generating SELECT statements. It handles PostgreSQL-specific syntax like LIMIT/OFFSET (instead of TOP) and the string concatenation operator || src/EFCore.PG/Query/Internal/NpgsqlQuerySqlGenerator.cs14-15 src/EFCore.PG/Query/Internal/NpgsqlQuerySqlGenerator.cs116-130
• NpgsqlMigrationsSqlGenerator: Responsible for generating DDL (Data Definition Language). It manages PostgreSQL-specific features like UNLOGGED tables and COMMENT ON syntax src/EFCore.PG/Migrations/NpgsqlMigrationsSqlGenerator.cs24-25 src/EFCore.PG/Migrations/NpgsqlMigrationsSqlGenerator.cs175-189

Scaffolding (Reverse Engineering)

The process of reading an existing PostgreSQL database schema and generating EF Core model code.

• NpgsqlDatabaseModelFactory: Connects to a live database and queries system catalogs (like pg_attribute, pg_type) to build a DatabaseModel src/EFCore.PG/Scaffolding/Internal/NpgsqlDatabaseModelFactory.cs18-19 src/EFCore.PG/Scaffolding/Internal/NpgsqlDatabaseModelFactory.cs196-205

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PostgreSQL-Specific Terminology

Term	Definition	Code Reference
JSONB	Binary-stored JSON format in PostgreSQL. Optimized for indexing and querying.	NpgsqlJsonTypeMapping src/EFCore.PG/Storage/Internal/Mapping/NpgsqlJsonTypeMapping.cs1-10
Search Vector	A tsvector type used for Full-Text Search.	NpgsqlTsVector test/EFCore.PG.FunctionalTests/BuiltInDataTypesNpgsqlTest.cs116
Identity Column	The modern SQL-standard way to handle auto-incrementing columns (PostgreSQL 10+).	NpgsqlValueGenerationStrategy.IdentityByDefaultColumn src/EFCore.PG/Migrations/NpgsqlMigrationsSqlGenerator.cs84-85
Serial Column	The legacy PostgreSQL auto-incrementing column type (e.g., SERIAL4).	NpgsqlValueGenerationStrategy.SerialColumn src/EFCore.PG/Migrations/NpgsqlMigrationsSqlGenerator.cs86
Unlogged Table	A table that is not written to the Write-Ahead Log (WAL), making it faster but not crash-safe.	NpgsqlAnnotationNames.UnloggedTable src/EFCore.PG/Migrations/NpgsqlMigrationsSqlGenerator.cs175-176

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Code Entity Mapping

The following diagrams bridge natural language concepts to the specific classes and methods implementing them in the provider.

Type Mapping Resolution Flow

This diagram shows how a CLR type (e.g., string) is resolved to a PostgreSQL type (e.g., text or citext).

Sources: src/EFCore.PG/Storage/Internal/NpgsqlTypeMappingSource.cs57 src/EFCore.PG/Storage/Internal/NpgsqlTypeMappingSource.cs81-86

Query Translation Pipeline

This diagram tracks how a LINQ expression is converted into PostgreSQL-specific SQL.

Sources: src/EFCore.PG/Query/Internal/NpgsqlSqlTranslatingExpressionVisitor.cs20-24 src/EFCore.PG/Query/NpgsqlSqlExpressionFactory.cs15-16 src/EFCore.PG/Query/Internal/NpgsqlQuerySqlGenerator.cs51-70

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Internal Abbreviations & Jargon

• NTS: NetTopologySuite. Refers to the spatial data plugin test/EFCore.PG.Tests/Storage/NpgsqlTypeMappingSourceTest.cs5
• PocoTranslator: A component that translates access to .NET properties inside a JSON column into PostgreSQL JSON traversal operators (->, ->>, #>) src/EFCore.PG/Query/Internal/NpgsqlSqlTranslatingExpressionVisitor.cs29-30
• Legacy Timestamp Behavior: A compatibility switch (Npgsql.EnableLegacyTimestampBehavior) that reverts DateTime mapping to the pre-6.0 behavior where DateTimeKind was largely ignored src/EFCore.PG/Storage/Internal/NpgsqlTypeMappingSource.cs31-37
• Admin Database: A database used to connect to the server when performing operations like CREATE DATABASE, where the target database does not yet exist src/EFCore.PG/Infrastructure/Internal/NpgsqlOptionsExtension.cs67
• Sequence Bumping: The process of updating a PostgreSQL SEQUENCE after data seeding to prevent primary key collisions src/EFCore.PG/Migrations/NpgsqlMigrationsSqlGenerator.cs71-74

Sources:

• src/EFCore.PG/Storage/Internal/NpgsqlTypeMappingSource.cs23-124
• src/EFCore.PG/Query/Internal/NpgsqlQuerySqlGenerator.cs14-160
• src/EFCore.PG/Migrations/NpgsqlMigrationsSqlGenerator.cs24-189
• src/EFCore.PG/Scaffolding/Internal/NpgsqlDatabaseModelFactory.cs18-205
• src/EFCore.PG/Query/Internal/NpgsqlSqlTranslatingExpressionVisitor.cs20-130
• src/EFCore.PG/Infrastructure/Internal/NpgsqlOptionsExtension.cs30-149