From 13b6fa65d2c7f1f7cfc9d8b097bc6ffa026a64e6 Mon Sep 17 00:00:00 2001
From: Andrew Golovashevich <landgrafhomyak@gmail.com>
Date: Sat, 1 Feb 2025 00:39:48 +0300
Subject: [PATCH] Mechanism for reducing rows ('COUNT()', 'SUM()' etc. from
 SQL)

---
 .../api/misc/BuiltinExpressionsProvider.kt    |  4 --
 .../db/serdha0/api/misc/Expression.kt         | 41 -----------
 .../db/serdha0/api/misc/Mapper.kt             | 41 +++++++++++
 .../db/serdha0/api/misc/Reducer.kt            | 41 +++++++++++
 .../serdha0/api/queries/QueryConstructor.kt   |  2 +-
 .../db/serdha0/api/queries/SelectQuery.kt     | 72 +++++++++++++++----
 .../db/serdha0/api/table/CheckConstraint.kt   | 10 ++-
 .../db/serdha0/api/table/DefaultConstraint.kt | 10 ++-
 8 files changed, 150 insertions(+), 71 deletions(-)
 delete mode 100644 src/commonMain/kotlin/ru/landgrafhomyak/db/serdha0/api/misc/BuiltinExpressionsProvider.kt
 delete mode 100644 src/commonMain/kotlin/ru/landgrafhomyak/db/serdha0/api/misc/Expression.kt
 create mode 100644 src/commonMain/kotlin/ru/landgrafhomyak/db/serdha0/api/misc/Mapper.kt
 create mode 100644 src/commonMain/kotlin/ru/landgrafhomyak/db/serdha0/api/misc/Reducer.kt

diff --git a/src/commonMain/kotlin/ru/landgrafhomyak/db/serdha0/api/misc/BuiltinExpressionsProvider.kt b/src/commonMain/kotlin/ru/landgrafhomyak/db/serdha0/api/misc/BuiltinExpressionsProvider.kt
deleted file mode 100644
index d26b862..0000000
--- a/src/commonMain/kotlin/ru/landgrafhomyak/db/serdha0/api/misc/BuiltinExpressionsProvider.kt
+++ /dev/null
@@ -1,4 +0,0 @@
-package ru.landgrafhomyak.db.serdha0.api.misc
-
-public interface BuiltinExpressionsProvider<OwnerQueryUserExtension: Any> {
-}
\ No newline at end of file
diff --git a/src/commonMain/kotlin/ru/landgrafhomyak/db/serdha0/api/misc/Expression.kt b/src/commonMain/kotlin/ru/landgrafhomyak/db/serdha0/api/misc/Expression.kt
deleted file mode 100644
index 14c0ba5..0000000
--- a/src/commonMain/kotlin/ru/landgrafhomyak/db/serdha0/api/misc/Expression.kt
+++ /dev/null
@@ -1,41 +0,0 @@
-package ru.landgrafhomyak.db.serdha0.api.misc
-
-import ru.landgrafhomyak.db.serdha0.api.runtime.InputRow
-import ru.landgrafhomyak.db.serdha0.api.runtime.OutputRow
-
-public interface Expression<ExpressionUserExtension : Any> {
-	public val userExtension: ExpressionUserExtension
-
-	public interface RuntimeExpressionInput<RT, DT : DatabaseType<RT>, ExpressionUserExtension : Any> : Column<RT, DT, ExpressionUserExtension>
-	public interface RuntimeExpressionOutput<RT, DT : DatabaseType<RT>, ExpressionUserExtension : Any> : QueryParam<RT, DT, ExpressionUserExtension>
-
-	public fun interface InputLinker<ExpressionUserExtension : Any, QueryUserExtension : Any> {
-		public fun link(linker: Scope<ExpressionUserExtension, QueryUserExtension>)
-
-		public interface Scope<ExpressionUserExtension : Any, QueryUserExtension : Any> {
-			public operator fun <RT, DT : DatabaseType<RT>> set(p: RuntimeExpressionInput<RT, DT, ExpressionUserExtension>, e: IntermediateColumn<RT, DT, QueryUserExtension>)
-		}
-	}
-
-	public fun interface OutputLinker<ExpressionUserExtension : Any, QueryUserExtension : Any> {
-		public fun link(linker: Scope<ExpressionUserExtension, QueryUserExtension>)
-
-		public interface Scope<ExpressionUserExtension : Any, QueryUserExtension : Any> {
-			public operator fun <RT, DT : DatabaseType<RT>> get(p: RuntimeExpressionOutput<RT, DT, ExpressionUserExtension>): IntermediateColumn<RT, DT, QueryUserExtension>
-		}
-	}
-
-	public interface Creator<ExpressionUserExtension : Any> {
-		public fun createExpression(creator: Scope<ExpressionUserExtension>): ExpressionUserExtension
-
-		public interface Scope<ExpressionUserExtension : Any> {
-			public fun <RT, DT : DatabaseType<RT>> input(name: String, type: DT): RuntimeExpressionInput<RT, DT, ExpressionUserExtension>
-			public fun <RT, DT : DatabaseType<RT>> output(name: String, type: DT): RuntimeExpressionOutput<RT, DT, ExpressionUserExtension>
-			public var action: Action<ExpressionUserExtension>
-		}
-	}
-
-	public interface Action<ExpressionUserExtension : Any> {
-		public fun calculate(input: OutputRow<ExpressionUserExtension>, output: InputRow<ExpressionUserExtension>)
-	}
-}
\ No newline at end of file
diff --git a/src/commonMain/kotlin/ru/landgrafhomyak/db/serdha0/api/misc/Mapper.kt b/src/commonMain/kotlin/ru/landgrafhomyak/db/serdha0/api/misc/Mapper.kt
new file mode 100644
index 0000000..643df09
--- /dev/null
+++ b/src/commonMain/kotlin/ru/landgrafhomyak/db/serdha0/api/misc/Mapper.kt
@@ -0,0 +1,41 @@
+package ru.landgrafhomyak.db.serdha0.api.misc
+
+import ru.landgrafhomyak.db.serdha0.api.runtime.InputRow
+import ru.landgrafhomyak.db.serdha0.api.runtime.OutputRow
+
+public interface Mapper<mUE : Any> {
+	public val userExtension: mUE
+
+	public interface InputColumn<RT, DT : DatabaseType<RT>, mUE : Any> : Column<RT, DT, mUE>
+	public interface OutputColumn<RT, DT : DatabaseType<RT>, mUE : Any> : QueryParam<RT, DT, mUE>
+
+	public fun interface InputLinker<mUE : Any, qUE : Any> {
+		public fun link(linker: Scope<mUE, qUE>)
+
+		public interface Scope<mUE : Any, qUE : Any> {
+			public operator fun <RT, DT : DatabaseType<RT>> set(p: InputColumn<RT, DT, mUE>, e: IntermediateColumn<RT, DT, qUE>)
+		}
+	}
+
+	public fun interface OutputLinker<mUE : Any, qUE : Any, oUE : Any> {
+		public fun link(linker: Scope<mUE, qUE>): oUE
+
+		public interface Scope<ExpressionUserExtension : Any, QueryUserExtension : Any> {
+			public operator fun <RT, DT : DatabaseType<RT>> get(p: OutputColumn<RT, DT, ExpressionUserExtension>): IntermediateColumn<RT, DT, QueryUserExtension>
+		}
+	}
+
+	public interface Constructor<mUE : Any> {
+		public fun createMapper(context: Scope<mUE>): mUE
+
+		public interface Scope<mUE : Any> {
+			public fun <RT, DT : DatabaseType<RT>> input(name: String, type: DT): InputColumn<RT, DT, mUE>
+			public fun <RT, DT : DatabaseType<RT>> output(name: String, type: DT): OutputColumn<RT, DT, mUE>
+			public var action: Action<mUE>
+		}
+	}
+
+	public interface Action<mUE : Any> {
+		public fun calculate(ue: mUE, input: OutputRow<mUE>, output: InputRow<mUE>)
+	}
+}
\ No newline at end of file
diff --git a/src/commonMain/kotlin/ru/landgrafhomyak/db/serdha0/api/misc/Reducer.kt b/src/commonMain/kotlin/ru/landgrafhomyak/db/serdha0/api/misc/Reducer.kt
new file mode 100644
index 0000000..ff2a769
--- /dev/null
+++ b/src/commonMain/kotlin/ru/landgrafhomyak/db/serdha0/api/misc/Reducer.kt
@@ -0,0 +1,41 @@
+package ru.landgrafhomyak.db.serdha0.api.misc
+
+import ru.landgrafhomyak.db.serdha0.api.runtime.InputRow
+import ru.landgrafhomyak.db.serdha0.api.runtime.OutputRow
+
+public interface Reducer<rUE : Any> {
+	public val userExtension: rUE
+
+	public interface IOColumn<RT, DT : DatabaseType<RT>, rUE : Any> : Column<RT, DT, rUE>, QueryParam<RT, DT, rUE>
+
+
+	public fun interface ReduceLinker<rUE : Any, qUE : Any, oUE : Any> {
+		public fun link(linker: Scope<rUE, qUE>): oUE
+
+		public interface Scope<rUE : Any, qUE : Any> {
+			public fun <RT, DT : DatabaseType<RT>> link(io: IOColumn<RT, DT, rUE>, src: IntermediateColumn<RT, DT, rUE>): IntermediateColumn<RT, DT, qUE>
+		}
+	}
+
+	public fun interface FoldLinker<rUE : Any, qUE : Any, oUE : Any> {
+		public fun link(linker: Scope<rUE, qUE>): oUE
+
+		public interface Scope<rUE : Any, qUE : Any> {
+			public fun <RT, DT : DatabaseType<RT>> link(io: IOColumn<RT, DT, rUE>, src: IntermediateColumn<RT, DT, rUE>, initial: RT): IntermediateColumn<RT, DT, qUE>
+			public fun <RT, DT : DatabaseType<RT>> link(io: IOColumn<RT, DT, rUE>, src: IntermediateColumn<RT, DT, rUE>, initial: QueryParam<RT, DT, qUE>): IntermediateColumn<RT, DT, qUE>
+		}
+	}
+
+	public interface Constructor<rUE : Any> {
+		public fun createReducer(creator: Scope<rUE>): rUE
+
+		public interface Scope<rUE : Any> {
+			public fun <RT, DT : DatabaseType<RT>> io(name: String, type: DT): IOColumn<RT, DT, rUE>
+			public var action: Action<rUE>
+		}
+	}
+
+	public interface Action<rUE : Any> {
+		public fun calculate(ue: rUE, acc: OutputRow<rUE>, row: OutputRow<rUE>, newAcc: InputRow<rUE>)
+	}
+}
\ No newline at end of file
diff --git a/src/commonMain/kotlin/ru/landgrafhomyak/db/serdha0/api/queries/QueryConstructor.kt b/src/commonMain/kotlin/ru/landgrafhomyak/db/serdha0/api/queries/QueryConstructor.kt
index a723240..8a5926d 100644
--- a/src/commonMain/kotlin/ru/landgrafhomyak/db/serdha0/api/queries/QueryConstructor.kt
+++ b/src/commonMain/kotlin/ru/landgrafhomyak/db/serdha0/api/queries/QueryConstructor.kt
@@ -15,7 +15,7 @@ public interface QueryConstructor<qUE : Any> {
 		public fun <qUE : Any, tUE : Any, sUE : Any> insertFromSubquery(table: Table<tUE, *>, selector: _Selectable<sUE>, creator: InsertQuery.FromSubquery.Constructor<qUE, tUE, sUE>): InsertQuery.FromSubquery<qUE>
 		public fun <qUE : Any, tUE : Any> insertMultipleRows(table: Table<tUE, *>, creator: InsertQuery.MultipleRows.Constructor<qUE, tUE>): InsertQuery.MultipleRows<qUE>
 
-		public fun <qUE : Any, tUE : Any> select(table: _Selectable<tUE>, creator: SelectQuery.FromTable.Constructor<qUE, tUE>): SelectQuery.FromTable<qUE>
+		public fun <qUE : Any, tUE : Any> select(table: _Selectable<tUE>, creator: SelectQuery.Simple.Constructor<qUE, tUE>): SelectQuery.Simple<qUE>
 		public fun <qUE : Any, lUE : Any, rUE : Any> selectWithJoin(left: _Selectable<lUE>, right: _Selectable<rUE>, creator: SelectQuery.WithJoin.Constructor<qUE, lUE, rUE>): SelectQuery.WithJoin<qUE>
 
 		public fun <qUE : Any, tUE : Any> updateSingleRow(table: Table<tUE, *>, creator: UpdateQuery.SingleRow.Constructor<qUE, tUE>): UpdateQuery.SingleRow<qUE>
diff --git a/src/commonMain/kotlin/ru/landgrafhomyak/db/serdha0/api/queries/SelectQuery.kt b/src/commonMain/kotlin/ru/landgrafhomyak/db/serdha0/api/queries/SelectQuery.kt
index ef90513..82fc682 100644
--- a/src/commonMain/kotlin/ru/landgrafhomyak/db/serdha0/api/queries/SelectQuery.kt
+++ b/src/commonMain/kotlin/ru/landgrafhomyak/db/serdha0/api/queries/SelectQuery.kt
@@ -1,12 +1,12 @@
 package ru.landgrafhomyak.db.serdha0.api.queries
 
-import ru.landgrafhomyak.db.serdha0.api.misc.BuiltinExpressionsProvider
 import ru.landgrafhomyak.db.serdha0.api.misc.Column
 import ru.landgrafhomyak.db.serdha0.api.misc.IntermediateColumn
 import ru.landgrafhomyak.db.serdha0.api.misc.DatabaseType
-import ru.landgrafhomyak.db.serdha0.api.misc.Expression
+import ru.landgrafhomyak.db.serdha0.api.misc.Mapper
 import ru.landgrafhomyak.db.serdha0.api.misc.FiltersScope
 import ru.landgrafhomyak.db.serdha0.api.misc.QueryParam
+import ru.landgrafhomyak.db.serdha0.api.misc.Reducer
 import ru.landgrafhomyak.db.serdha0.api.misc._Selectable
 import ru.landgrafhomyak.db.serdha0.api.runtime.InputRow
 
@@ -34,12 +34,12 @@ public interface SelectQuery<qUE : Any> : _Query<qUE> {
 		public fun <RT, DT : DatabaseType<RT>> queryParam(name: String, type: DT): QueryParam<RT, DT, qUE>
 		public fun <RT, DT : DatabaseType<RT>> paramAsColumn(param: QueryParam<RT, DT, qUE>): IntermediateColumn<RT, DT, qUE>
 
-		public val builtinExpressions: BuiltinExpressionsProvider<qUE>
-		public fun <eUE : Any> mapColumns(
-			expression: Expression<eUE>,
-			input: Expression.InputLinker<eUE, qUE>,
-			output: Expression.OutputLinker<eUE, qUE>
-		)
+		public fun <mUE : Any> createMapper(constructor: Mapper.Constructor<mUE>): Mapper<mUE>
+		public fun <mUE : Any, oUE : Any> mapColumns(
+			mapper: Mapper<mUE>,
+			input: Mapper.InputLinker<mUE, qUE>,
+			output: Mapper.OutputLinker<mUE, qUE, oUE>
+		): oUE
 
 		public val filters: FiltersScope<qUE>
 		public fun orderBy(order: Order, vararg column: IntermediateColumn<*, *, qUE>)
@@ -51,6 +51,21 @@ public interface SelectQuery<qUE : Any> : _Query<qUE> {
 		public fun <RT, DT : DatabaseType<RT>> returnColumn(name: String, column: IntermediateColumn<RT, DT, qUE>): Column<RT, DT, qUE>
 	}
 
+	public interface Simple<qUE : Any> : SelectQuery<qUE>, _Query.Params2Table<qUE> {
+		public interface Constructor<qUE : Any, tUE : Any> {
+			public val source: _Selectable<tUE>
+
+			public fun createSelect(context: Scope<qUE, tUE>): qUE
+
+			public interface Scope<qUE : Any, tUE : Any> : _CommonSelectCreatorScope<qUE> {
+				public val sUExt: tUE
+				public val subqueryParams: InputRow.WithRedirect<tUE, qUE>
+
+				public fun <RT, DT : DatabaseType<RT>> selectColumnFromSubquery(param: Column<RT, DT, tUE>): IntermediateColumn<RT, DT, qUE>
+			}
+		}
+	}
+
 	public interface WithJoin<qUE : Any> : SelectQuery<qUE>, _Query.Params2Table<qUE> {
 		public interface Constructor<qUE : Any, lsqUE : Any, rsqUE : Any> : _CommonSelectCreatorScope<qUE> {
 			public val left: _Selectable<lsqUE>
@@ -75,17 +90,48 @@ public interface SelectQuery<qUE : Any> : _Query<qUE> {
 		}
 	}
 
-	public interface FromTable<qUE : Any> : SelectQuery<qUE>, _Query.Params2Table<qUE> {
+	public interface Reduce<qUE : Any> : SelectQuery<qUE>, _Query.Params2Table<qUE> {
 		public interface Constructor<qUE : Any, tUE : Any> {
-			public val table: _Selectable<tUE>
+			public val source: _Selectable<tUE>
 
-			public fun createSelect(context: Scope<qUE, tUE>): qUE
+			public fun createSelectWithReduce(context: Scope<qUE, tUE>): qUE
 
 			public interface Scope<qUE : Any, tUE : Any> : _CommonSelectCreatorScope<qUE> {
-				public val tUExt: tUE
-				public val subqueryParams: InputRow.WithRedirect<tUE, qUE>
+				public val sUExt: tUE
+				public val sourceParams: InputRow.WithRedirect<tUE, qUE>
 
 				public fun <RT, DT : DatabaseType<RT>> selectColumnFromSubquery(param: Column<RT, DT, tUE>): IntermediateColumn<RT, DT, qUE>
+
+				public fun <rUE : Any> createReducer(constructor: Reducer.Constructor<rUE>): Reducer<rUE>
+				public fun <mUE : Any, oUE : Any> reduceRows(
+					reducer: Reducer<mUE>,
+					linker: Reducer.ReduceLinker<mUE, qUE, oUE>,
+				): oUE
+
+				public fun groupBy(vararg columns: IntermediateColumn<*, *, qUE>)
+			}
+		}
+	}
+
+	public interface Fold<qUE : Any> : SelectQuery<qUE>, _Query.Params2Table<qUE> {
+		public interface Constructor<qUE : Any, tUE : Any> {
+			public val source: _Selectable<tUE>
+
+			public fun createSelectWithFold(context: Scope<qUE, tUE>): qUE
+
+			public interface Scope<qUE : Any, tUE : Any> : _CommonSelectCreatorScope<qUE> {
+				public val sUExt: tUE
+				public val sourceParams: InputRow.WithRedirect<tUE, qUE>
+
+				public fun <RT, DT : DatabaseType<RT>> selectColumnFromSubquery(param: Column<RT, DT, tUE>): IntermediateColumn<RT, DT, qUE>
+
+				public fun <rUE : Any> createReducer(constructor: Reducer.Constructor<rUE>): Reducer<rUE>
+				public fun <mUE : Any, oUE : Any> foldRows(
+					reducer: Reducer<mUE>,
+					linker: Reducer.FoldLinker<mUE, qUE, oUE>,
+				): oUE
+
+				public fun groupBy(vararg columns: IntermediateColumn<*, *, qUE>)
 			}
 		}
 	}
diff --git a/src/commonMain/kotlin/ru/landgrafhomyak/db/serdha0/api/table/CheckConstraint.kt b/src/commonMain/kotlin/ru/landgrafhomyak/db/serdha0/api/table/CheckConstraint.kt
index 35e918b..b52bbd6 100644
--- a/src/commonMain/kotlin/ru/landgrafhomyak/db/serdha0/api/table/CheckConstraint.kt
+++ b/src/commonMain/kotlin/ru/landgrafhomyak/db/serdha0/api/table/CheckConstraint.kt
@@ -1,11 +1,10 @@
 package ru.landgrafhomyak.db.serdha0.api.table
 
 import kotlin.jvm.JvmName
-import ru.landgrafhomyak.db.serdha0.api.misc.BuiltinExpressionsProvider
 import ru.landgrafhomyak.db.serdha0.api.misc.Column
 import ru.landgrafhomyak.db.serdha0.api.misc.IntermediateColumn
 import ru.landgrafhomyak.db.serdha0.api.misc.DatabaseType
-import ru.landgrafhomyak.db.serdha0.api.misc.Expression
+import ru.landgrafhomyak.db.serdha0.api.misc.Mapper
 
 public interface CheckConstraint<tUE : Any> {
 	@Suppress("INAPPLICABLE_JVM_NAME")
@@ -30,11 +29,10 @@ public interface CheckConstraint<tUE : Any> {
 				column: Column<RT, DT, rtUE>
 			): IntermediateColumn<RT, DT, rtUE>
 
-			public val builtinExpressions: BuiltinExpressionsProvider<cUE>
 			public fun <eUE : Any> mapColumns(
-				expression: Expression<eUE>,
-				input: Expression.InputLinker<eUE, cUE>,
-				output: Expression.OutputLinker<eUE, cUE>
+				expression: Mapper<eUE>,
+				input: ru.landgrafhomyak.db.serdha0.api.misc.Expression.Map.InputLinker<eUE, cUE>,
+				output: ru.landgrafhomyak.db.serdha0.api.misc.Expression.Map.OutputLinker<eUE, cUE>
 			)
 		}
 	}
diff --git a/src/commonMain/kotlin/ru/landgrafhomyak/db/serdha0/api/table/DefaultConstraint.kt b/src/commonMain/kotlin/ru/landgrafhomyak/db/serdha0/api/table/DefaultConstraint.kt
index 64533e8..55a8cb5 100644
--- a/src/commonMain/kotlin/ru/landgrafhomyak/db/serdha0/api/table/DefaultConstraint.kt
+++ b/src/commonMain/kotlin/ru/landgrafhomyak/db/serdha0/api/table/DefaultConstraint.kt
@@ -1,11 +1,10 @@
 package ru.landgrafhomyak.db.serdha0.api.table
 
 import kotlin.jvm.JvmName
-import ru.landgrafhomyak.db.serdha0.api.misc.BuiltinExpressionsProvider
 import ru.landgrafhomyak.db.serdha0.api.misc.Column
 import ru.landgrafhomyak.db.serdha0.api.misc.IntermediateColumn
 import ru.landgrafhomyak.db.serdha0.api.misc.DatabaseType
-import ru.landgrafhomyak.db.serdha0.api.misc.Expression
+import ru.landgrafhomyak.db.serdha0.api.misc.Mapper
 
 public interface DefaultConstraint<tUE : Any> {
 	@Suppress("INAPPLICABLE_JVM_NAME")
@@ -30,11 +29,10 @@ public interface DefaultConstraint<tUE : Any> {
 				column: Column<RT, DT, rtUE>
 			): IntermediateColumn<RT, DT, rtUE>
 
-			public val builtinExpressions: BuiltinExpressionsProvider<cUE>
 			public fun <eUE : Any> mapColumns(
-				expression: Expression<eUE>,
-				input: Expression.InputLinker<eUE, cUE>,
-				output: Expression.OutputLinker<eUE, cUE>
+				expression: Mapper<eUE>,
+				input: ru.landgrafhomyak.db.serdha0.api.misc.Expression.Map.InputLinker<eUE, cUE>,
+				output: ru.landgrafhomyak.db.serdha0.api.misc.Expression.Map.OutputLinker<eUE, cUE>
 			)
 		}
 	}