Adds a built-in PartiQL System catalog, support for SQL-Path, and SPI cleanup

partiql-spi/api/partiql-spi.api

@@ -70,6 +70,7 @@ public class org/partiql/spi/SourceLocations : java/util/Map {
 public abstract interface class org/partiql/spi/catalog/Catalog {
 	public static final field Companion Lorg/partiql/spi/catalog/Catalog$Companion;
 	public static fun builder ()Lorg/partiql/spi/catalog/Catalog$Builder;
+	public static fun empty (Ljava/lang/String;)Lorg/partiql/spi/catalog/Catalog;
 	public abstract fun getAggregations (Lorg/partiql/spi/catalog/Session;Ljava/lang/String;)Ljava/util/Collection;
 	public abstract fun getFunctions (Lorg/partiql/spi/catalog/Session;Ljava/lang/String;)Ljava/util/Collection;
 	public abstract fun getName ()Ljava/lang/String;
@@ -85,6 +86,7 @@ public final class org/partiql/spi/catalog/Catalog$Builder {
 
 public final class org/partiql/spi/catalog/Catalog$Companion {
 	public final fun builder ()Lorg/partiql/spi/catalog/Catalog$Builder;
+	public final fun empty (Ljava/lang/String;)Lorg/partiql/spi/catalog/Catalog;
 }
 
 public final class org/partiql/spi/catalog/Catalog$DefaultImpls {
@@ -97,7 +99,6 @@ public final class org/partiql/spi/catalog/Catalog$DefaultImpls {
 public abstract interface class org/partiql/spi/catalog/Catalogs {
 	public static final field Companion Lorg/partiql/spi/catalog/Catalogs$Companion;
 	public static fun builder ()Lorg/partiql/spi/catalog/Catalogs$Builder;
-	public static fun empty ()Lorg/partiql/spi/catalog/Catalogs;
 	public abstract fun getCatalog (Ljava/lang/String;Z)Lorg/partiql/spi/catalog/Catalog;
 	public static fun of (Ljava/util/Collection;)Lorg/partiql/spi/catalog/Catalogs;
 	public static fun of ([Lorg/partiql/spi/catalog/Catalog;)Lorg/partiql/spi/catalog/Catalogs;
@@ -111,7 +112,6 @@ public final class org/partiql/spi/catalog/Catalogs$Builder {
 
 public final class org/partiql/spi/catalog/Catalogs$Companion {
 	public final fun builder ()Lorg/partiql/spi/catalog/Catalogs$Builder;
-	public final fun empty ()Lorg/partiql/spi/catalog/Catalogs;
 	public final fun of (Ljava/util/Collection;)Lorg/partiql/spi/catalog/Catalogs;
 	public final fun of ([Lorg/partiql/spi/catalog/Catalog;)Lorg/partiql/spi/catalog/Catalogs;
 }
@@ -261,6 +261,7 @@ public final class org/partiql/spi/catalog/Session$Builder {
 	public final fun namespace (Lorg/partiql/spi/catalog/Namespace;)Lorg/partiql/spi/catalog/Session$Builder;
 	public final fun namespace ([Ljava/lang/String;)Lorg/partiql/spi/catalog/Session$Builder;
 	public final fun property (Ljava/lang/String;Ljava/lang/String;)Lorg/partiql/spi/catalog/Session$Builder;
+	public final fun system (Lorg/partiql/spi/catalog/Catalog;)Lorg/partiql/spi/catalog/Session$Builder;
 }
 
 public final class org/partiql/spi/catalog/Session$Companion {

partiql-spi/src/main/java/org/partiql/spi/catalog/PartiQLSystemCatalog.java

@@ -0,0 +1,60 @@
+package org.partiql.spi.catalog;
+
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+import org.partiql.spi.function.Aggregation;
+import org.partiql.spi.function.Builtins;
+import org.partiql.spi.function.Function;
+
+import java.util.Collection;
+
+/**
+ * <p>
+ * This package-private class implements the PartiQL System Catalog.
+ * </p>
+ * <p>
+ * It provides the implementation for the PartiQL System Catalog, which is a built-in catalog
+ * that provides access to the PartiQL language and its built-in functions and aggregations.
+ * </p>
+ * @see Session.Builder
+ */
+final class PartiQLSystemCatalog implements Catalog {
+
+    @NotNull
+    private static final String NAME = "$system";
+
+    /**
+     * This is a package-private singleton.
+     */
+    static PartiQLSystemCatalog INSTANCE = new PartiQLSystemCatalog();
+
+    @NotNull
+    @Override
+    public String getName() {
+        return NAME;
+    }
+
+    @Nullable
+    @Override
+    public Table getTable(@NotNull Session session, @NotNull Name name) {
+        return null;
+    }
+
+    @Nullable
+    @Override
+    public Table getTable(@NotNull Session session, @NotNull Identifier identifier) {
+        return null;
+    }
+
+    @NotNull
+    @Override
+    public Collection<Function> getFunctions(@NotNull Session session, @NotNull String name) {
+        return Builtins.INSTANCE.getFunctions(name);
+    }
+
+    @NotNull
+    @Override
+    public Collection<Aggregation> getAggregations(@NotNull Session session, @NotNull String name) {
+        return Builtins.INSTANCE.getAggregations(name);
+    }
+}

partiql-spi/src/main/kotlin/org/partiql/spi/catalog/Catalog.kt

@@ -57,6 +57,19 @@ public interface Catalog {
 
         @JvmStatic
         public fun builder(): Builder = Builder()
+
+        /**
+         * @return an empty catalog with the given name
+         * @param name the catalog name
+         */
+        @JvmStatic
+        public fun empty(name: String): Catalog {
+            return object : Catalog {
+                override fun getName(): String = name
+                override fun getTable(session: Session, name: Name): Table? = null
+                override fun getTable(session: Session, identifier: Identifier): Table? = null
+            }
+        }
     }
 
     /**

partiql-spi/src/main/kotlin/org/partiql/spi/catalog/Catalogs.kt

@@ -25,20 +25,6 @@ public interface Catalogs {
             return builder().apply { catalogs.forEach { add(it) } }.build()
         }
 
-        /**
-         * A catalog provider that always returns an empty catalog.
-         */
-        @JvmStatic
-        public fun empty(): Catalogs = object : Catalogs {
-            private val EMPTY = object : Catalog {
-                override fun getName(): String = "empty"
-                override fun getTable(session: Session, name: Name): Table? = null
-                override fun getTable(session: Session, identifier: Identifier): Table? = null
-            }
-
-            override fun getCatalog(name: String, ignoreCase: Boolean): Catalog = EMPTY
-        }
-
         @JvmStatic
         public fun builder(): Builder = Builder()
     }

partiql-spi/src/main/kotlin/org/partiql/spi/catalog/Session.kt

@@ -46,11 +46,9 @@ public interface Session {
          * Returns a [Session] with only the "empty" catalog implementation.
          */
         @JvmStatic
-        public fun empty(): Session = object : Session {
-            override fun getIdentity(): String = "unknown"
-            override fun getCatalog(): String = "empty"
-            override fun getCatalogs(): Catalogs = Catalogs.empty()
-            override fun getNamespace(): Namespace = Namespace.empty()
+        public fun empty(): Session {
+            val catalog = Catalog.empty("empty")
+            return builder().catalog(catalog.getName()).catalogs(catalog).build()
         }
 
         @JvmStatic
@@ -64,6 +62,7 @@ public interface Session {
 
         private var identity: String = "unknown"
         private var catalog: String? = null
+        private var systemCatalog: Catalog = PartiQLSystemCatalog.INSTANCE
         private var catalogs: Catalogs.Builder = Catalogs.builder()
         private var namespace: Namespace = Namespace.empty()
         private var properties: MutableMap<String, String> = mutableMapOf()
@@ -98,6 +97,16 @@ public interface Session {
             return this
         }
 
+        /**
+         * Adds and designates a catalog to always be on the SQL-Path. This [catalog] provides all built-in functions
+         * to the system at hand.
+         * If this is never invoked, a default system catalog is provided.
+         */
+        public fun system(catalog: Catalog): Builder {
+            this.systemCatalog = catalog
+            return this
+        }
+
         /**
          * Adds catalogs to this session.
          */
@@ -110,16 +119,24 @@ public interface Session {
 
         public fun build(): Session = object : Session {
 
-            private val _catalogs = catalogs.build()
+            private val _catalogs: Catalogs
+            private val systemCatalogNamespace: Namespace = Namespace.of(systemCatalog.getName())
 
             init {
                 require(catalog != null) { "Session catalog must be set" }
+                catalogs.add(systemCatalog)
+                _catalogs = catalogs.build()
             }
 
             override fun getIdentity(): String = identity
             override fun getCatalog(): String = catalog!!
             override fun getCatalogs(): Catalogs = _catalogs
             override fun getNamespace(): Namespace = namespace
+
+            override fun getPath(): Path {
+                val currentNamespace = getNamespace()
+                return Path.of(currentNamespace, systemCatalogNamespace)
+            }
         }
     }
 }