HHH-19712 Rework select fragment generation to work with column selection deduplication

Author: beikov

hibernate-core/src/main/java/org/hibernate/persister/entity/AbstractEntityPersister.java

@@ -1999,63 +1999,59 @@ public String selectFragment(String alias, String suffix) {
 		// Wrap expressions with aliases
 		final SelectClause selectClause = rootQuerySpec.getSelectClause();
 		final List<SqlSelection> sqlSelections = selectClause.getSqlSelections();
+		final Set<String> processedExpressions = new HashSet<>( sqlSelections.size() );
 		int i = 0;
-		int columnIndex = 0;
-		final String[] columnAliases = getSubclassColumnAliasClosure();
-		final int columnAliasesSize = columnAliases.length;
-		for ( String identifierAlias : identifierAliases ) {
-			sqlSelections.set(
-					i,
-					new SqlSelectionImpl(
-							i,
-							new AliasedExpression( sqlSelections.get( i ).getExpression(), identifierAlias + suffix )
-					)
-			);
-			if ( i < columnAliasesSize && columnAliases[i].equals( identifierAlias ) ) {
-				columnIndex++;
+		final int identifierSelectionSize = identifierMapping.getJdbcTypeCount();
+		for ( int j = 0; j < identifierSelectionSize; j++ ) {
+			final SelectableMapping selectableMapping = identifierMapping.getSelectable( j );
+			if ( processedExpressions.add( selectableMapping.getSelectionExpression() ) ) {
+				aliasSelection( sqlSelections, i, identifierAliases[j] + suffix );
+				i++;
 			}
-			i++;
 		}
 
-		if ( entityMetamodel.hasSubclasses() ) {
-			sqlSelections.set(
-					i,
-					new SqlSelectionImpl(
-							i,
-							new AliasedExpression( sqlSelections.get( i ).getExpression(), getDiscriminatorAlias() + suffix )
-					)
-			);
-			i++;
+		if ( hasSubclasses() ) {
+			assert discriminatorMapping.getJdbcTypeCount() == 1;
+			final SelectableMapping selectableMapping = discriminatorMapping.getSelectable( 0 );
+			if ( processedExpressions.add( selectableMapping.getSelectionExpression() ) ) {
+				aliasSelection( sqlSelections, i, getDiscriminatorAlias() + suffix );
+				i++;
+			}
 		}
 
 		if ( hasRowId() ) {
-			sqlSelections.set(
-					i,
-					new SqlSelectionImpl(
-							i,
-							new AliasedExpression( sqlSelections.get( i ).getExpression(), ROWID_ALIAS + suffix )
-					)
-			);
-			i++;
-		}
-
-		final String[] formulaAliases = getSubclassFormulaAliasClosure();
-		int formulaIndex = 0;
-		for ( ; i < sqlSelections.size(); i++ ) {
-			final SqlSelection sqlSelection = sqlSelections.get( i );
-			final ColumnReference columnReference = (ColumnReference) sqlSelection.getExpression();
-			final String selectAlias = !columnReference.isColumnExpressionFormula()
-					? columnAliases[columnIndex++] + suffix
-					: formulaAliases[formulaIndex++] + suffix;
-			sqlSelections.set(
-					i,
-					new SqlSelectionImpl(
-							sqlSelection.getValuesArrayPosition(),
-							new AliasedExpression( sqlSelection.getExpression(), selectAlias )
-					)
-			);
+			final SelectableMapping selectableMapping = rowIdMapping;
+			if ( processedExpressions.add( selectableMapping.getSelectionExpression() ) ) {
+				aliasSelection( sqlSelections, i, ROWID_ALIAS + suffix );
+				i++;
+			}
 		}
 
+		final String[] columnAliases = getSubclassColumnAliasClosure();
+		final String[] formulaAliases = getSubclassFormulaAliasClosure();// getSubclassColumnAliasClosure contains the _identifierMapper columns,
+        // which need to be skipped
+        int columnIndex = identifierMapping instanceof NonAggregatedIdentifierMapping ? identifierSelectionSize : 0;
+        int formulaIndex = 0;
+        final int size = getNumberOfFetchables();
+        for ( int j = 0; j < size; j++ ) {
+            final AttributeMapping fetchable = getFetchable( j );
+            if ( !(fetchable instanceof PluralAttributeMapping)
+                    && !skipFetchable( fetchable, fetchable.getMappedFetchOptions().getTiming() )
+                    && fetchable.isSelectable() ) {
+                final int jdbcTypeCount = fetchable.getJdbcTypeCount();
+                for ( int k = 0; k < jdbcTypeCount; k++ ) {
+                    final SelectableMapping selectableMapping = fetchable.getSelectable( k );
+                    if ( processedExpressions.add( selectableMapping.getSelectionExpression() ) ) {
+                        final String baseAlias = selectableMapping.isFormula()
+                                ? formulaAliases[formulaIndex++]
+                                : columnAliases[columnIndex++];
+                        aliasSelection( sqlSelections, i, baseAlias + suffix );
+                        i++;
+                    }
+                }
+            }
+        }
+
 		final String sql = getFactory().getJdbcServices()
 				.getDialect()
 				.getSqlAstTranslatorFactory()
@@ -2073,6 +2069,17 @@ public String selectFragment(String alias, String suffix) {
 		return expression;
 	}
 
+	private static void aliasSelection(
+			List<SqlSelection> sqlSelections,
+			int selectionIndex,
+			String alias) {
+		final Expression expression = sqlSelections.get( selectionIndex ).getExpression();
+		sqlSelections.set(
+				selectionIndex,
+				new SqlSelectionImpl( selectionIndex, new AliasedExpression( expression, alias ) )
+		);
+	}
+
 	private ImmutableFetchList fetchProcessor(FetchParent fetchParent, LoaderSqlAstCreationState creationState) {
 		final FetchableContainer fetchableContainer = fetchParent.getReferencedMappingContainer();
 		final int size = fetchableContainer.getNumberOfFetchables();
@@ -2083,45 +2090,45 @@ private ImmutableFetchList fetchProcessor(FetchParent fetchParent, LoaderSqlAstC
 			// Ignore plural attributes
 			if ( !( fetchable instanceof PluralAttributeMapping ) ) {
 				final FetchTiming fetchTiming = fetchable.getMappedFetchOptions().getTiming();
-				if ( fetchable.asBasicValuedModelPart() != null ) {
-					// Ignore lazy basic columns
-					if ( fetchTiming == FetchTiming.DELAYED ) {
-						continue;
-					}
-				}
-				else if ( fetchable instanceof Association ) {
-					final Association association = (Association) fetchable;
-					// Ignore the fetchable if the FK is on the other side
-					if ( association.getSideNature() == ForeignKeyDescriptor.Nature.TARGET ) {
-						continue;
-					}
-					// Ensure the FK comes from the root table
-					if ( !getRootTableName().equals( association.getForeignKeyDescriptor().getKeyTable() ) ) {
-						continue;
-					}
-				}
-
-				if ( fetchTiming == null ) {
-					throw new AssertionFailure("fetchTiming was null");
-				}
-
-				if ( fetchable.isSelectable() ) {
-					final Fetch fetch = fetchParent.generateFetchableFetch(
-							fetchable,
-							fetchParent.resolveNavigablePath( fetchable ),
-							fetchTiming,
-							false,
-							null,
-							creationState
-					);
-					fetches.add( fetch );
-				}
+                if ( !skipFetchable( fetchable, fetchTiming ) ) {
+                    if ( fetchTiming == null ) {
+                        throw new AssertionFailure( "fetchTiming was null" );
+                    }
+                    if ( fetchable.isSelectable() ) {
+                        final Fetch fetch = fetchParent.generateFetchableFetch(
+                                fetchable,
+                                fetchParent.resolveNavigablePath( fetchable ),
+                                fetchTiming,
+                                false,
+                                null,
+                                creationState
+                        );
+                        fetches.add( fetch );
+                    }
+                }
 			}
 		}
 
 		return fetches.build();
 	}
 
+    private boolean skipFetchable(Fetchable fetchable, FetchTiming fetchTiming) {
+        if ( fetchable.asBasicValuedModelPart() != null ) {
+            // Ignore lazy basic columns
+            return fetchTiming == FetchTiming.DELAYED;
+        }
+        else if ( fetchable instanceof Association ) {
+            final Association association = (Association) fetchable;
+            // Ignore the fetchable if the FK is on the other side
+            return association.getSideNature() == ForeignKeyDescriptor.Nature.TARGET
+                    // Ensure the FK comes from the root table
+                    || !getRootTableName().equals( association.getForeignKeyDescriptor().getKeyTable() );
+        }
+        else {
+            return false;
+        }
+    }
+
 	/**
 	 * @deprecated use {@link Fetchable#isSelectable()} instead.
 	 */
@@ -6354,7 +6361,7 @@ public Fetchable getKeyFetchable(int position) {
 	}
 
 	@Override
-	public Fetchable getFetchable(int position) {
+	public AttributeMapping getFetchable(int position) {
 		return getStaticFetchableList().get( position );
 	}