feat: define SQL AST node types

src/main/kotlin/kestrel/sql/ast/Ast.kt

@@ -0,0 +1,103 @@
+package kestrel.sql.ast
+
+import kestrel.catalog.Column
+import kestrel.storage.Value
+
+sealed interface Statement
+
+data class CreateTableStatement(val tableName: String, val columns: List<Column>) : Statement
+
+data class DropTableStatement(val tableName: String) : Statement
+
+data class CreateIndexStatement(
+    val indexName: String,
+    val tableName: String,
+    val columnName: String
+) : Statement
+
+data class DropIndexStatement(val indexName: String) : Statement
+
+data class InsertStatement(
+    val tableName: String,
+    val columns: List<String>?,
+    val rows: List<List<Expression>>
+) : Statement
+
+data class SelectStatement(
+    val projection: Projection,
+    val tableName: String,
+    val tableAlias: String? = null,
+    val joins: List<JoinClause> = emptyList(),
+    val where: Expression? = null,
+    val groupBy: List<Expression> = emptyList(),
+    val having: Expression? = null,
+    val orderBy: OrderBy? = null,
+    val limit: Int? = null
+) : Statement
+
+data class DeleteStatement(val tableName: String, val where: Expression?) : Statement
+
+data class UpdateStatement(
+    val tableName: String,
+    val assignments: List<Assignment>,
+    val where: Expression?
+) : Statement
+
+data class ExplainStatement(val select: SelectStatement) : Statement
+
+data object BeginStatement : Statement
+
+data object CommitStatement : Statement
+
+data object RollbackStatement : Statement
+
+data class Assignment(val columnName: String, val value: Expression)
+
+enum class JoinType { Inner, Left }
+
+data class JoinClause(
+    val type: JoinType,
+    val tableName: String,
+    val alias: String?,
+    val on: Expression
+)
+
+sealed interface Projection
+
+data object StarProjection : Projection
+
+data class ExpressionProjection(val items: List<SelectItem>) : Projection
+
+data class SelectItem(val expression: Expression, val alias: String?)
+
+data class OrderBy(val expression: Expression, val descending: Boolean)
+
+sealed interface Expression
+
+data class LiteralExpression(val value: Value) : Expression
+
+data class ColumnExpression(val name: String, val qualifier: String? = null) : Expression
+
+data class FunctionExpression(
+    val name: String,
+    val argument: Expression?,
+    val star: Boolean
+) : Expression
+
+data class BinaryExpression(
+    val operator: BinaryOperator,
+    val left: Expression,
+    val right: Expression
+) : Expression
+
+data class UnaryExpression(val operator: UnaryOperator, val operand: Expression) : Expression
+
+enum class BinaryOperator(val symbol: String) {
+    Add("+"), Subtract("-"), Multiply("*"), Divide("/"),
+    Equal("="), NotEqual("<>"), Less("<"), LessEqual("<="),
+    Greater(">"), GreaterEqual(">="), And("AND"), Or("OR")
+}
+
+enum class UnaryOperator(val symbol: String) {
+    Negate("-"), Not("NOT")
+}