Examples with ExpressionReplacementWalker org.hibernate.sql.ast.spi.ExpressionReplacementWalker used on opensource projects

Example 1 with ExpressionReplacementWalker

use of org.hibernate.sql.ast.spi.ExpressionReplacementWalker in project hibernate-orm by hibernate.

the class AggregateWindowEmulationQueryTransformer method transform.

@Override
public QuerySpec transform(CteContainer cteContainer, QuerySpec querySpec, SqmToSqlAstConverter converter) {
    final SessionFactoryImplementor factory = converter.getCreationContext().getSessionFactory();
    final QuerySpec outerQuerySpec = new QuerySpec(querySpec.isRoot());
    final String identifierVariable = "hhh_";
    final NavigablePath navigablePath = new NavigablePath(identifierVariable, identifierVariable);
    final SelectClause selectClause = outerQuerySpec.getSelectClause();
    final QuerySpec subQuerySpec = querySpec.asSubQuery();
    final SelectClause subSelectClause = subQuerySpec.getSelectClause();
    final List<SqlSelection> subSelections = subSelectClause.getSqlSelections();
    final List<String> columnNames = new ArrayList<>(subSelections.size());
    // A map to find the select item position for an expression
    // which is needed to decide if we need to introduce synthetic select items
    // for group by items, since these group by items are migrated to the outer query
    final Map<Expression, Integer> selectionMapping = new HashMap<>(subSelections.size());
    // for the QueryPartTableGroup within which the sub query spec is embedded
    for (int i = 0; i < subSelections.size(); i++) {
        final BasicValuedMapping mapping = (BasicValuedMapping) subSelections.get(i).getExpressionType();
        final String columnName = "col" + i;
        final ColumnReference columnReference = new ColumnReference(identifierVariable, columnName, false, null, null, mapping.getJdbcMapping(), factory);
        final Expression expression = subSelections.get(i).getExpression();
        final Expression finalExpression;
        if (expression == windowFunction) {
            finalExpression = new SelfRenderingAggregateFunctionSqlAstExpression("min", (sqlAppender, sqlAstArguments, walker1) -> {
                sqlAppender.appendSql("min(");
                sqlAstArguments.get(0).accept(walker1);
                sqlAppender.append(')');
            }, Collections.singletonList(columnReference), null, (ReturnableType<?>) mapping.getMappedType(), expression.getExpressionType());
        } else {
            finalExpression = columnReference;
            selectionMapping.put(expression, i);
        }
        columnNames.add(columnName);
        selectClause.addSqlSelection(new ResolvedSqlSelection(i + 1, i, finalExpression, (BasicType<Object>) mapping.getJdbcMapping()));
    }
    // Migrate the group by clause to the outer query
    // and push group by expressions into the partition by clause of the window function
    final List<Expression> groupByExpressions = new ArrayList<>(subQuerySpec.getGroupByClauseExpressions().size());
    for (Expression groupByClauseExpression : subQuerySpec.getGroupByClauseExpressions()) {
        final Expression realExpression;
        final Expression outerGroupByExpression;
        if (groupByClauseExpression instanceof SqlSelectionExpression) {
            final SqlSelection selection = ((SqlSelectionExpression) groupByClauseExpression).getSelection();
            outerGroupByExpression = new SqlSelectionExpression(selectClause.getSqlSelections().get(selection.getValuesArrayPosition()));
            realExpression = selection.getExpression();
        } else {
            if (groupByClauseExpression instanceof SqmPathInterpretation<?>) {
                realExpression = ((SqmPathInterpretation<?>) groupByClauseExpression).getSqlExpression();
            } else {
                realExpression = groupByClauseExpression;
            }
            final Integer position = selectionMapping.get(realExpression);
            if (position == null) {
                // Group by something that has no corresponding selection item,
                // so we need to introduce an intermediate selection item
                final int valuesPosition = selectClause.getSqlSelections().size();
                final String columnName = "col" + valuesPosition;
                final JdbcMapping jdbcMapping = realExpression.getExpressionType().getJdbcMappings().get(0);
                final ColumnReference columnReference = new ColumnReference(identifierVariable, columnName, false, null, null, jdbcMapping, factory);
                final int subValuesPosition = subSelectClause.getSqlSelections().size();
                final SqlSelection subSelection = new ResolvedSqlSelection(subValuesPosition + 1, subValuesPosition, realExpression, (BasicType<Object>) jdbcMapping);
                columnNames.add(columnName);
                subSelectClause.addSqlSelection(subSelection);
                outerGroupByExpression = columnReference;
                selectionMapping.put(realExpression, subValuesPosition);
            } else {
                outerGroupByExpression = new SqlSelectionExpression(selectClause.getSqlSelections().get(position));
            }
        }
        windowFunction.getPartitions().add(realExpression);
        groupByExpressions.add(outerGroupByExpression);
    }
    outerQuerySpec.setGroupByClauseExpressions(groupByExpressions);
    subQuerySpec.setGroupByClauseExpressions(null);
    // Migrate the having clause to the outer query
    if (subQuerySpec.getHavingClauseRestrictions() != null) {
        final Predicate predicate = new ExpressionReplacementWalker() {

            @Override
            protected <X extends SqlAstNode> X replaceExpression(X expression) {
                if (expression instanceof Literal || expression instanceof JdbcParameter) {
                    return expression;
                }
                final Expression outerExpression;
                if (expression instanceof SqlSelectionExpression) {
                    final SqlSelection selection = ((SqlSelectionExpression) expression).getSelection();
                    outerExpression = selectClause.getSqlSelections().get(selection.getValuesArrayPosition()).getExpression();
                } else {
                    final Expression realExpression;
                    if (expression instanceof SqmPathInterpretation<?>) {
                        realExpression = ((SqmPathInterpretation<?>) expression).getSqlExpression();
                    } else {
                        realExpression = (Expression) expression;
                    }
                    final Integer position = selectionMapping.get(realExpression);
                    if (position == null) {
                        // An expression that has no corresponding selection item,
                        // so we need to introduce an intermediate selection item
                        final int valuesPosition = selectClause.getSqlSelections().size();
                        final String columnName = "col" + valuesPosition;
                        final JdbcMapping jdbcMapping = realExpression.getExpressionType().getJdbcMappings().get(0);
                        final ColumnReference columnReference = new ColumnReference(identifierVariable, columnName, false, null, null, jdbcMapping, factory);
                        final int subValuesPosition = subSelectClause.getSqlSelections().size();
                        final SqlSelection subSelection = new ResolvedSqlSelection(subValuesPosition + 1, subValuesPosition, realExpression, (BasicType<Object>) jdbcMapping);
                        columnNames.add(columnName);
                        subSelectClause.addSqlSelection(subSelection);
                        outerExpression = columnReference;
                        selectionMapping.put(realExpression, subValuesPosition);
                    } else {
                        outerExpression = selectClause.getSqlSelections().get(position).getExpression();
                    }
                }
                return (X) outerExpression;
            }
        }.replaceExpressions(subQuerySpec.getHavingClauseRestrictions());
        outerQuerySpec.setHavingClauseRestrictions(predicate);
        subQuerySpec.setHavingClauseRestrictions(null);
    }
    // Migrate the order by clause to the outer query
    if (subQuerySpec.hasSortSpecifications()) {
        for (SortSpecification sortSpecification : subQuerySpec.getSortSpecifications()) {
            final Expression sortExpression = sortSpecification.getSortExpression();
            final Expression outerSortExpression;
            if (sortExpression instanceof SqlSelectionExpression) {
                final SqlSelection selection = ((SqlSelectionExpression) sortExpression).getSelection();
                outerSortExpression = new SqlSelectionExpression(selectClause.getSqlSelections().get(selection.getValuesArrayPosition()));
            } else {
                final Expression realExpression;
                if (sortExpression instanceof SqmPathInterpretation<?>) {
                    realExpression = ((SqmPathInterpretation<?>) sortExpression).getSqlExpression();
                } else {
                    realExpression = sortExpression;
                }
                final Integer position = selectionMapping.get(realExpression);
                if (position == null) {
                    // Group by something that has no corresponding selection item,
                    // so we need to introduce an intermediate selection item
                    final int valuesPosition = selectClause.getSqlSelections().size();
                    final String columnName = "col" + valuesPosition;
                    final JdbcMapping jdbcMapping = realExpression.getExpressionType().getJdbcMappings().get(0);
                    final ColumnReference columnReference = new ColumnReference(identifierVariable, columnName, false, null, null, jdbcMapping, factory);
                    final int subValuesPosition = subSelectClause.getSqlSelections().size();
                    final SqlSelection subSelection = new ResolvedSqlSelection(subValuesPosition + 1, subValuesPosition, realExpression, (BasicType<Object>) jdbcMapping);
                    columnNames.add(columnName);
                    subSelectClause.addSqlSelection(subSelection);
                    outerSortExpression = columnReference;
                    selectionMapping.put(realExpression, subValuesPosition);
                } else {
                    outerSortExpression = new SqlSelectionExpression(selectClause.getSqlSelections().get(position));
                }
            }
            outerQuerySpec.addSortSpecification(new SortSpecification(outerSortExpression, sortSpecification.getSortOrder(), sortSpecification.getNullPrecedence()));
        }
        subQuerySpec.getSortSpecifications().clear();
    }
    // We need to add selection items for the expressions we order by to the sub query spec.
    final int selectionOffset = columnNames.size();
    // Collect the sorting column references so we can apply the filter later
    final List<ColumnReference> sortingColumns = new ArrayList<>(withinGroup.size());
    for (int i = 0; i < withinGroup.size(); i++) {
        final int valueIndex = selectionOffset + i;
        final Expression sortExpression = withinGroup.get(i).getSortExpression();
        final BasicValuedMapping mapping = (BasicValuedMapping) sortExpression.getExpressionType();
        final String columnName = "col" + valueIndex;
        final int oldValueIndex = subSelectClause.getSqlSelections().size();
        columnNames.add(columnName);
        subSelectClause.addSqlSelection(new ResolvedSqlSelection(oldValueIndex + 1, oldValueIndex, sortExpression, (BasicType<Object>) mapping.getJdbcMapping()));
        sortingColumns.add(new ColumnReference(identifierVariable, columnName, false, null, null, mapping.getJdbcMapping(), factory));
    }
    if (arguments != null) {
        // So we add a filter to the outer query so we can extract the rank
        switch(arguments.size()) {
            case 0:
                break;
            case 1:
                outerQuerySpec.applyPredicate(new ComparisonPredicate(sortingColumns.get(0), ComparisonOperator.EQUAL, (Expression) arguments.get(0)));
                break;
            default:
                outerQuerySpec.applyPredicate(new ComparisonPredicate(new SqlTuple(sortingColumns, null), ComparisonOperator.EQUAL, new SqlTuple((List<? extends Expression>) (List<?>) arguments, null)));
        }
    }
    final QueryPartTableGroup queryPartTableGroup = new QueryPartTableGroup(navigablePath, null, subQuerySpec, identifierVariable, columnNames, false, true, factory);
    outerQuerySpec.getFromClause().addRoot(queryPartTableGroup);
    // Migrate the offset/fetch clause
    outerQuerySpec.setOffsetClauseExpression(subQuerySpec.getOffsetClauseExpression());
    outerQuerySpec.setFetchClauseExpression(subQuerySpec.getFetchClauseExpression(), subQuerySpec.getFetchClauseType());
    subQuerySpec.setOffsetClauseExpression(null);
    subQuerySpec.setFetchClauseExpression(null, null);
    return outerQuerySpec;
}