Scala

Installation

Add to your build.sbt:

libraryDependencies += "io.github.edadma" %%% "petradb-engine" % "1.5.0"

Package Structure

PetraDB is split across two packages:

• io.github.edadma.petradb — shared types (Result, Value, Row, TableValue, Session trait)
• io.github.edadma.petradb.engine — the database engine (MemoryDB, PersistentDB, TextDB, Session, executeSQL)

Import both to use the engine directly:

import io.github.edadma.petradb.*
import io.github.edadma.petradb.engine.*

In-Memory Database

import io.github.edadma.petradb.*
import io.github.edadma.petradb.engine.*

given Session = new MemoryDB().connect()

Persistent Database

import io.github.edadma.petradb.*
import io.github.edadma.petradb.engine.*

// Create new
val db = PersistentDB.create("path/to/db", pageSize = 4096)
given Session = db.connect()

// Reopen existing
val db = PersistentDB.open("path/to/db")
given Session = db.connect()

// Close when done
db.close()

Text Database

import io.github.edadma.petradb.*
import io.github.edadma.petradb.engine.*

val db = TextDB.open("path/to/data.ptxt")
given Session = db.connect()

db.close()

Human-readable .ptxt file. Loads into memory on open, rewrites after every change. Works on JVM and Native.

Executing SQL

executeSQL(sql: String)(using Session): Seq[Result]

Executes one or more semicolon-separated SQL statements and returns a sequence of results.

val results: Seq[Result] = executeSQL("SELECT * FROM users")

Result Types

sealed trait Result
case class QueryResult(table: TableValue)                           extends Result
case class InsertResult(obj: Map[String, Value], table: TableValue) extends Result
case class CreateTableResult(table: String)                         extends Result
case class DropTableResult(table: String)                           extends Result
case class CreateIndexResult(name: String)                          extends Result
case class DropIndexResult(name: String)                            extends Result
case class CreateTypeResult(typ: String)                            extends Result
case class DropTypeResult(name: String)                             extends Result
case class CreateViewResult(name: String)                           extends Result
case class DropViewResult(name: String)                             extends Result
case class CreateSequenceResult(name: String)                       extends Result
case class DropSequenceResult(name: String)                         extends Result
case class UpdateResult(rows: Int)                                  extends Result
case class DeleteResult(rows: Int)                                  extends Result
case class TruncateResult(table: String)                            extends Result
case class AlterTableResult()                                       extends Result
case class ExplainResult(plan: String)                              extends Result
case class PrepareResult(name: String)                              extends Result
case class DeallocateResult(name: String)                           extends Result
case class CopyResult(rows: Int)                                    extends Result
case class CreateSchemaResult(name: String)                         extends Result
case object BeginResult                                             extends Result
case object CommitResult                                            extends Result
case object RollbackResult                                          extends Result
case object DoBlockResult                                           extends Result
case class CreateFunctionResult(name: String)                       extends Result
case class DropFunctionResult(name: String)                         extends Result
case class CreateProcedureResult(name: String)                      extends Result
case class DropProcedureResult(name: String)                        extends Result
case class CreateTriggerResult(name: String)                        extends Result
case class DropTriggerResult(name: String)                          extends Result
case object CallResult                                              extends Result

Accessing Query Data

val QueryResult(table) = executeQuery("SELECT * FROM users")

// Access rows
val rows: IndexedSeq[Row] = table.data

for (row <- table.data) {
  val id: Int = row.getInt("id")
  val name: String = row.getString("name")
  val email: Option[String] = row.getStringOption("email")
}

User-Defined Functions

Register native Scala functions callable from SQL, triggers, and stored procedures:

db.registerScalarFunction("my_double", {
  case Seq(v) => NumberValue(v.intValue * 2)
}, NumberType)

// Now usable in SQL:
// SELECT my_double(age) FROM users;

Functions registered this way work everywhere: SELECT, WHERE, DO blocks, stored functions, and triggers.

Value Extraction

val row: Row = table.data.head

// Type-safe extraction
val id: Int = row.getInt("id")
val name: String = row.getString("name")
val email: Option[String] = row.getStringOption("email")
val isActive: Boolean = row.getBoolean("is_active")

// Direct access
val value: Value = row("column_name")