Database Connectors Connectors implement database-specific validation, native types, and capabilities. They extend the generic PSL validation with provider-specific logic.
Connector Trait The Connector trait defines the interface for all database connectors:
pub trait Connector : Send + Sync { fn provider_name ( & self ) -> & ' static str ; fn is_provider ( & self , name : & str ) -> bool ; fn flavour ( & self ) -> Flavour ; fn name ( & self ) -> & str ; fn capabilities ( & self ) -> ConnectorCapabilities ; fn max_identifier_length ( & self ) -> usize ; // Relation modes and referential actions fn allowed_relation_mode_settings ( & self ) -> BitFlags < RelationMode >; fn default_relation_mode ( & self ) -> RelationMode ; fn referential_actions ( & self , mode : & RelationMode ) -> BitFlags < ReferentialAction >; // Native types fn available_native_type_constructors ( & self ) -> & [ NativeTypeConstructor ]; fn scalar_type_for_native_type ( & self , native_type : & NativeTypeInstance ) -> Option < ScalarFieldType >; fn default_native_type_for_scalar_type ( & self , scalar_type : & ScalarFieldType ) -> Option < NativeTypeInstance >; // Validations fn validate_model ( & self , model : ModelWalker <' _ >, relation_mode : RelationMode , diagnostics : & mut Diagnostics ); fn validate_enum ( & self , enum_ : EnumWalker <' _ >, diagnostics : & mut Diagnostics ); fn validate_datasource ( & self , preview_features : BitFlags < PreviewFeature >, datasource : & Datasource , diagnostics : & mut Diagnostics ); // ... more validation methods }
Connectors are stateless - all methods take &self. Configuration and state live in the Datasource type.
Built-in Connectors PSL provides connectors for all supported databases:
pub static BUILTIN_CONNECTORS : ConnectorRegistry <' static > = & [ #[cfg(feature = "postgresql" )] POSTGRES , #[cfg(feature = "mysql" )] MYSQL , #[cfg(feature = "sqlite" )] SQLITE , #[cfg(feature = "mssql" )] MSSQL , #[cfg(feature = "cockroachdb" )] COCKROACH , #[cfg(feature = "mongodb" )] MONGODB , ];
PostgreSQL Connector Provider: postgresqlCapabilities: pub const CAPABILITIES : ConnectorCapabilities = make_bitflags! ( ConnectorCapability :: { AdvancedJsonNullability | AnyId | AutoIncrement | AutoIncrementAllowedOnNonId | AutoIncrementMultipleAllowed | AutoIncrementNonIndexedAllowed | CompoundIds | CreateMany | CreateManyWriteableAutoIncId | CreateSkipDuplicates | Enums | EnumArrayPush | NativeFullTextSearch | NativeFullTextSearchWithoutIndex | InsensitiveFilters | Json | JsonFiltering | JsonFilteringArrayPath | JsonFilteringAlphanumeric | JsonArrayContains | MultiSchema | NamedForeignKeys | NamedPrimaryKeys | RelationFieldsInArbitraryOrder | ScalarLists | JsonLists | UpdateableId | WritableAutoincField | ImplicitManyToManyRelation | DecimalType | OrderByNullsFirstLast | InsertReturning | UpdateReturning | DeleteReturning | SupportsFiltersOnRelationsWithoutJoins | LateralJoin | PartialIndex });
Native Types: pub enum PostgresType { SmallInt , Integer , BigInt , Decimal ( Option <( u32 , u32 )>), Money , Real , DoublePrecision , SmallSerial , Serial , BigSerial , VarChar ( Option < u32 >), Char ( Option < u32 >), Text , ByteA , Timestamp ( Option < u32 >), Timestamptz ( Option < u32 >), Date , Time ( Option < u32 >), Timetz ( Option < u32 >), Boolean , Bit ( Option < u32 >), VarBit ( Option < u32 >), Uuid , Xml , Json , JsonB , Inet , Oid , }
Special Features:
Extensions support (e.g., postgis, uuid-ossp)
Multi-schema support
Advanced indexing (GIN, GIST, BRIN)
Full-text search
Partial indexes with WHERE clauses
MySQL Connector Provider: mysqlCapabilities: pub const CAPABILITIES : ConnectorCapabilities = make_bitflags! ( ConnectorCapability :: { Enums | EnumArrayPush | Json | AutoIncrementAllowedOnNonId | RelationFieldsInArbitraryOrder | CreateMany | WritableAutoincField | CreateSkipDuplicates | UpdateableId | JsonFiltering | JsonFilteringJsonPath | JsonFilteringAlphanumeric | JsonArrayContains | CreateManyWriteableAutoIncId | AutoIncrement | CompoundIds | AnyId | NamedForeignKeys | AdvancedJsonNullability | IndexColumnLengthPrefixing | FullTextIndex | NativeFullTextSearch | NativeFullTextSearchWithIndex | MultipleFullTextAttributesPerModel | ImplicitManyToManyRelation | DecimalType | OrderByNullsFirstLast | RowIn | SupportsFiltersOnRelationsWithoutJoins | CorrelatedSubqueries });
Native Types: pub enum MySqlType { TinyInt , SmallInt , MediumInt , Int , BigInt , Decimal ( Option <( u32 , u32 )>), Float , Double , Bit ( u32 ), Char ( u32 ), VarChar ( u32 ), Binary ( u32 ), VarBinary ( u32 ), TinyBlob , Blob , MediumBlob , LongBlob , TinyText , Text , MediumText , LongText , Date , Time ( Option < u32 >), DateTime ( Option < u32 >), Timestamp ( Option < u32 >), Year , Json , }
Special Features:
Index column length prefixing
Full-text indexes
Multiple character sets
Enum type support
SQLite Connector Provider: sqliteCapabilities: pub const CAPABILITIES : ConnectorCapabilities = make_bitflags! ( ConnectorCapability :: { CompoundIds | AnyId | RelationFieldsInArbitraryOrder | ImplicitManyToManyRelation | DecimalType | BackwardCompatibleQueryRaw | InsensitiveFilters | JsonFilteringAlphanumeric | OrderByNullsFirstLast });
Native Types: pub enum SqliteType { Integer , Real , Text , Blob , }
Limitations:
No enums (emulated as CHECK constraints)
No native JSON type (stored as TEXT)
Limited ALTER TABLE support
No foreign key actions in some configurations
SQL Server (MSSQL) Connector Provider: sqlserverCapabilities: pub const CAPABILITIES : ConnectorCapabilities = make_bitflags! ( ConnectorCapability :: { CompoundIds | AnyId | AutoIncrement | InsensitiveFilters | CreateMany | UpdateableId | Json | JsonFiltering | RelationFieldsInArbitraryOrder | ImplicitManyToManyRelation | DecimalType | OrderByNullsFirstLast });
Native Types: pub enum MsSqlType { TinyInt , SmallInt , Int , BigInt , Decimal ( Option <( u32 , u32 )>), Money , SmallMoney , Bit , Float ( Option < u32 >), Real , Date , Time , DateTime , DateTime2 , DateTimeOffset , SmallDateTime , Char ( Option < u32 >), NChar ( Option < u32 >), VarChar ( Option < MsSqlTypeParameter >), NVarChar ( Option < MsSqlTypeParameter >), Text , NText , Binary ( Option < u32 >), VarBinary ( Option < MsSqlTypeParameter >), Image , Xml , UniqueIdentifier , }
CockroachDB Connector Provider: cockroachdbFeatures:
Extends PostgreSQL connector
Distributed SQL capabilities
Some PostgreSQL features unsupported
pub enum CockroachType { // Similar to PostgresType with limitations Bit ( Option < u32 >), Char ( Option < u32 >), // ... etc }
MongoDB Connector Provider: mongodbStatus: Limited Query Compiler supportCapabilities: pub const CAPABILITIES : ConnectorCapabilities = make_bitflags! ( ConnectorCapability :: { Enums | Json | CompositeTypes | ScalarLists | JsonLists | RelationFieldsInArbitraryOrder | TwoWayEmbeddedManyToManyRelation | DefaultValueAuto | UndefinedType });
MongoDB support in Query Compiler is incomplete. Prisma 7 will ship without MongoDB initially, with support added when a driver adapter is available.
Connector Capabilities Capabilities describe what functionality a connector provides:
Schema Capabilities
Enums - Native enum supportScalarLists - Array/list fieldsJson - Native JSON typeJsonLists - JSON array supportCompositeTypes - Embedded/composite typesMultiSchema - Multiple database schemas
ID and Key Capabilities
AutoIncrement - Auto-incrementing IDsAutoIncrementAllowedOnNonId - Autoincrement on non-ID fieldsAutoIncrementMultipleAllowed - Multiple autoincrement fieldsCompoundIds - Multi-field primary keysAnyId - Any unique can serve as IDNamedPrimaryKeys - Custom primary key namesNamedForeignKeys - Custom foreign key names
Index Capabilities
FullTextIndex - Full-text search indexesIndexColumnLengthPrefixing - Index prefix length (MySQL)PartialIndex - Partial indexes with WHEREClusteringSetting - Clustered indexes
Query Capabilities
InsensitiveFilters - Case-insensitive filteringJsonFiltering - JSON field filteringJsonFilteringArrayPath - Array path in JSON (Postgres)JsonFilteringJsonPath - JSON path syntax (MySQL)NativeFullTextSearch - Full-text search queriesOrderByNullsFirstLast - NULL ordering controlLateralJoin - Lateral joinsDistinctOn - DISTINCT ON support
Write Capabilities
CreateMany - Batch insertsCreateSkipDuplicates - INSERT … ON CONFLICT DO NOTHINGCreateManyWriteableAutoIncId - Specify autoincrement values in batchWritableAutoincField - Override autoincrement valuesUpdateableId - Modify primary key valuesNativeUpsert - Native UPSERT supportInsertReturning - INSERT … RETURNINGUpdateReturning - UPDATE … RETURNINGDeleteReturning - DELETE … RETURNING
Transaction Capabilities
SupportsTxIsolationReadUncommittedSupportsTxIsolationReadCommittedSupportsTxIsolationRepeatableReadSupportsTxIsolationSerializableSupportsTxIsolationSnapshot
Relation Modes Connectors support different relation modes:
pub enum RelationMode { ForeignKeys , // Database foreign keys Prisma , // Emulated in Prisma Client }
Foreign Keys Mode Relations enforced by database constraints:
datasource db { provider = "postgresql" relationMode = "foreignKeys" // Default for most DBs } model Post { id Int @id authorId Int author User @relation ( fields : [ authorId ], references : [ id ], onDelete : Cascade ) }
Referential actions:
Cascade - Delete/update cascadesRestrict - Prevent if references existNoAction - Like Restrict, but deferrableSetNull - Set to NULLSetDefault - Set to default value
Prisma Mode Relations emulated by Prisma Client:
datasource db { provider = "mysql" relationMode = "prisma" // For PlanetScale, Neon, etc. } model Post { id Int @id authorId Int author User @relation ( fields : [ authorId ], references : [ id ] ) @@index ( [ authorId ] ) // Manual index required }
Prisma mode requires manual indexes on relation fields. The database won’t enforce referential integrity.
Native Type Validation Connectors validate native type usage:
fn validate_native_type_arguments ( & self , native_type : & NativeTypeInstance , scalar_type : Option < ScalarType >, span : Span , diagnostics : & mut Diagnostics , ) { // Check if native type is compatible with scalar type // Validate native type arguments (e.g., length, precision) }
Example:
model User { id Int @id name String @db.VarChar ( 255 ) // PostgreSQL native type age Int @db.SmallInt // Valid mapping bio String @db.Integer // ERROR: String can't use Integer }
Connector-Specific Validations Model Validation fn validate_model ( & self , model : ModelWalker <' _ >, relation_mode : RelationMode , diagnostics : & mut Diagnostics , ) { // Check model-level constraints // Validate indexes // Check capabilities }
Example validations:
Composite types only on MongoDB
Enum arrays only on supported databases
Multi-schema requirements
Enum Validation fn validate_enum ( & self , enum_ : EnumWalker <' _ >, diagnostics : & mut Diagnostics , ) { // Check if enums are supported // Validate enum values }
Datasource Validation fn validate_datasource ( & self , preview_features : BitFlags < PreviewFeature >, datasource : & Datasource , diagnostics : & mut Diagnostics , ) { // Validate preview features compatibility // Check datasource properties }
Flavour System Flavours group similar databases:
pub enum Flavour { Postgres , // PostgreSQL, Neon Mysql , // MySQL, PlanetScale Sqlite , // SQLite Mssql , // SQL Server Mongo , // MongoDB Cockroach , // CockroachDB (PostgreSQL-like) }
Flavours determine:
Query syntax variations
Type system similarities
Shared capabilities
Custom Connectors You can implement custom connectors for new databases:
use psl_core :: datamodel_connector ::* ; pub struct MyCustomConnector ; impl Connector for MyCustomConnector { fn provider_name ( & self ) -> & ' static str { "mycustomdb" } fn flavour ( & self ) -> Flavour { Flavour :: Postgres // Or your own } fn capabilities ( & self ) -> ConnectorCapabilities { make_bitflags! ( ConnectorCapability :: { Enums | Json | AutoIncrement | CompoundIds }) } // Implement remaining trait methods... }
Constraint Scopes Define where constraint names must be unique:
pub enum ConstraintScope { GlobalPrimaryKeyKeyIndex , ModelPrimaryKeyKeyIndexForeignKey , GlobalForeignKey , ModelKeyIndex , } fn constraint_violation_scopes ( & self ) -> & ' static [ ConstraintScope ] { & [ ConstraintScope :: GlobalPrimaryKeyKeyIndex , ConstraintScope :: ModelPrimaryKeyKeyIndexForeignKey , ] }
String Filters Connectors can customize available string operations:
pub enum StringFilter { StartsWith , EndsWith , Contains , Mode , // Case sensitivity Search , // Full-text search } fn string_filters ( & self , input_object_name : & str ) -> BitFlags < StringFilter > { match input_object_name { "String" => BitFlags :: all (), _ => BitFlags :: empty (), } }
Testing Connectors Test connector-specific behavior:
# Test with specific database features cargo test -p psl -F postgresql cargo test -p psl -F mysql cargo test -p psl -F all # Run against actual databases TEST_DATABASE_URL = postgresql://... cargo test -p sql-migration-tests
Next Steps
PSL Overview Return to PSL architecture overview
Validation Learn about the validation pipeline