[#2984] Add <R extends Record> Table<R> table(Result<R>) to allow to fetch from / join / etc in-memory tables

jOOQ-test/src/org/jooq/test/_/testcases/ValuesConstructorTests.java

@@ -42,6 +42,7 @@ package org.jooq.test._.testcases;
 
 import static junit.framework.Assert.assertEquals;
 import static org.jooq.impl.DSL.row;
+import static org.jooq.impl.DSL.table;
 import static org.jooq.impl.DSL.values;
 
 import java.sql.Date;
@@ -53,6 +54,7 @@ import org.jooq.Record3;
 import org.jooq.Record6;
 import org.jooq.Result;
 import org.jooq.RowN;
+import org.jooq.Table;
 import org.jooq.TableRecord;
 import org.jooq.UpdatableRecord;
 import org.jooq.test.BaseTest;
@@ -117,4 +119,25 @@ extends BaseTest<A, AP, B, S, B2S, BS, L, X, DATE, BOOL, D, T, U, UU, I, IPK, T7
 
         assertEquals(r1, r2);
     }
+
+    @Test
+    public void testResultConstructor() throws Exception {
+        Result<Record2<Integer, String>> booksResult =
+        create().select(TBook_ID(), TBook_TITLE())
+                .from(TBook())
+                .orderBy(TBook_ID())
+                .fetch();
+
+        Table<Record2<Integer, String>> booksTable = table(booksResult);
+
+        assertEquals(
+            booksResult,
+            create().selectFrom(booksTable).fetch());
+
+        assertEquals(
+            BOOK_IDS,
+            create().select(booksTable.field(TBook_ID()))
+                    .from(booksTable)
+                    .fetch(TBook_ID()));
+    }
 }

jOOQ-test/src/org/jooq/test/jOOQAbstractTest.java

@@ -1891,6 +1891,11 @@ public abstract class jOOQAbstractTest<
         new ValuesConstructorTests(this).testValuesConstructor();
     }
 
+    @Test
+    public void testResultConstructor() throws Exception {
+        new ValuesConstructorTests(this).testResultConstructor();
+    }
+
     @Test
     public void testOrderByInSubquery() throws Exception {
         new OrderByTests(this).testOrderByInSubquery();

jOOQ/src/main/java/org/jooq/impl/DSL.java

@@ -4489,6 +4489,33 @@ public class DSL {
         return select.asTable();
     }
 
+    /**
+     * Use a previously obtained result as a new {@link Table} that can be used
+     * in SQL statements through {@link #values(RowN...)}.
+     *
+     * @see #values(RowN...)
+     */
+    @Support
+    @Transition(
+        name = "TABLE",
+        args = "Result"
+    )
+    public static <R extends Record> Table<R> table(Result<R> result) {
+        int size = result.size();
+
+        RowN[] rows = new RowN[size];
+        for (int i = 0; i < size; i++)
+            rows[i] = (RowN) result.get(i).valuesRow();
+
+        Field<?>[] fields = result.fields();
+        String[] columns = new String[fields.length];
+        for (int i = 0; i < fields.length; i++)
+            columns[i] = fields[i].getName();
+
+        // TODO [#2986] Coerce the record type upon the resulting table.
+        return (Table<R>) values(rows).as("v", columns);
+    }
+
     /**
      * A synonym for {@link #unnest(List)}.
      *
@@ -12364,9 +12391,12 @@ public class DSL {
         args = "Row+"
     )
     public static Table<Record> values(RowN... rows) {
-        String[] columns = new String[rows.length];
+        Values.assertNotEmpty(rows);
+        int size = rows[0].size();
 
-        for (int i = 0; i < rows.length; i++)
+        String[] columns = new String[size];
+
+        for (int i = 0; i < size; i++)
             columns[i] = "c" + i;
 
         return new Values<Record>(rows).as("v", columns);

jOOQ/src/main/java/org/jooq/impl/Values.java

@@ -68,7 +68,14 @@ class Values<R extends Record> extends AbstractTable<R> {
     Values(Row[] rows) {
         super("values");
 
-        this.rows = rows;
+        this.rows = assertNotEmpty(rows);
+    }
+
+    static Row[] assertNotEmpty(Row[] rows) {
+        if (rows == null || rows.length == 0)
+            throw new IllegalArgumentException("Cannot create a VALUES() constructor with an empty set of rows");
+
+        return rows;
     }
 
     @SuppressWarnings("unchecked")