Package org.apache.calcite.rel.rel2sql

Class RelToSqlConverter

java.lang.Object

org.apache.calcite.rel.rel2sql.SqlImplementor

org.apache.calcite.rel.rel2sql.RelToSqlConverter

All Implemented Interfaces:

ReflectiveVisitor

Direct Known Subclasses:

JdbcImplementor, PigRelToSqlConverter

public class RelToSqlConverter
extends SqlImplementor
implements ReflectiveVisitor

Utility to convert relational expressions to SQL abstract syntax tree.

Nested Class Summary

Nested classes/interfaces inherited from class org.apache.calcite.rel.rel2sql.SqlImplementor

SqlImplementor.AliasContext, SqlImplementor.BaseContext, SqlImplementor.Builder, SqlImplementor.Clause, SqlImplementor.Context, SqlImplementor.MatchRecognizeContext, SqlImplementor.Result, SqlImplementor.SimpleContext

Field Summary

Fields inherited from class org.apache.calcite.rel.rel2sql.SqlImplementor

aliasSet, correlTableMap, dialect, POS

Constructor Summary

Constructors

Constructor	Description
RelToSqlConverter(SqlDialect dialect)	Creates a RelToSqlConverter.

Method Summary

Modifier and Type	Method	Description
void	addSelect(List<SqlNode> selectList, SqlNode node, RelDataType rowType)
protected void	buildAggGroupList(Aggregate e, SqlImplementor.Builder builder, List<SqlNode> groupByList, List<SqlNode> selectList)	Builds the group list for an Aggregate node.
protected SqlImplementor.Builder	buildAggregate(Aggregate e, SqlImplementor.Builder builder, List<SqlNode> selectList, List<SqlNode> groupByList)	Builds an aggregate query.
List<SqlNode>	createAsFullOperands(RelDataType rowType, SqlNode leftOperand, String alias)	Creates operands for a full AS operator.
protected SqlImplementor.Result	dispatch(RelNode e)	Dispatches a call to the visit(Xxx e) method where Xxx most closely matches the runtime type of the argument.
boolean	hasTrickyRollup(Sort e, Aggregate aggregate)
protected boolean	isAnon()	Returns whether to remove trivial aliases such as "EXPR$0" when converting the current relational expression into a SELECT.
protected SqlImplementor.Result	result(SqlNode node, Collection<SqlImplementor.Clause> clauses, @Nullable String neededAlias, @Nullable RelDataType neededType, Map<String,RelDataType> aliases)	Factory method for SqlImplementor.Result.
SqlImplementor.Result	visit(Aggregate e)	Visits an Aggregate; called by dispatch(org.apache.calcite.rel.RelNode) via reflection.
SqlImplementor.Result	visit(Calc e)	Visits a Calc; called by dispatch(org.apache.calcite.rel.RelNode) via reflection.
SqlImplementor.Result	visit(Correlate e)	Visits a Correlate; called by dispatch(org.apache.calcite.rel.RelNode) via reflection.
SqlImplementor.Result	visit(Filter e)	Visits a Filter; called by dispatch(org.apache.calcite.rel.RelNode) via reflection.
SqlImplementor.Result	visit(Intersect e)	Visits an Intersect; called by dispatch(org.apache.calcite.rel.RelNode) via reflection.
SqlImplementor.Result	visit(Join e)	Visits a Join; called by dispatch(org.apache.calcite.rel.RelNode) via reflection.
SqlImplementor.Result	visit(Match e)	Visits a Match; called by dispatch(org.apache.calcite.rel.RelNode) via reflection.
SqlImplementor.Result	visit(Minus e)	Visits a Minus; called by dispatch(org.apache.calcite.rel.RelNode) via reflection.
SqlImplementor.Result	visit(Project e)	Visits a Project and converts it to a SqlSelect.
SqlImplementor.Result	visit(Sample e)	Visits a Sample; called by dispatch(org.apache.calcite.rel.RelNode) via reflection.
SqlImplementor.Result	visit(Sort e)	Visits a Sort; called by dispatch(org.apache.calcite.rel.RelNode) via reflection.
SqlImplementor.Result	visit(TableFunctionScan e)
SqlImplementor.Result	visit(TableModify modify)	Visits a TableModify; called by dispatch(org.apache.calcite.rel.RelNode) via reflection.
SqlImplementor.Result	visit(TableScan e)	Visits a TableScan; called by dispatch(org.apache.calcite.rel.RelNode) via reflection.
SqlImplementor.Result	visit(Uncollect e)
SqlImplementor.Result	visit(Union e)	Visits a Union; called by dispatch(org.apache.calcite.rel.RelNode) via reflection.
SqlImplementor.Result	visit(Values e)	Visits a Values; called by dispatch(org.apache.calcite.rel.RelNode) via reflection.
SqlImplementor.Result	visit(Window e)	Visits a Window; called by dispatch(org.apache.calcite.rel.RelNode) via reflection.
SqlImplementor.Result	visit(RelNode e)	Visits a RelNode; called by dispatch(org.apache.calcite.rel.RelNode) via reflection.
protected SqlImplementor.Result	visitAntiOrSemiJoin(Join e)
SqlImplementor.Result	visitInput(RelNode parent, int i, boolean anon, boolean ignoreClauses, Set<SqlImplementor.Clause> expectedClauses)	Visits the ith input of e, the current relational expression.
protected SqlImplementor.Result	wrapNestedJoin(SqlImplementor.Result input, RelNode inputRel, String outerAlias)	Wraps a nested join into a subquery with explicit column aliases.

Methods inherited from class org.apache.calcite.rel.rel2sql.SqlImplementor

aliasContext, as, convertConditionToSqlNode, getAliasContext, isStar, isStar, joinContext, joinType, matchRecognizeContext, result, result, selectListContext, setOpToSql, tableFunctionScanContext, toSql, toSql, visitChild, visitInput, visitInput, visitInput, visitRoot, windowTableFunctionScanContext

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Details

RelToSqlConverter

public RelToSqlConverter(SqlDialect dialect)

Creates a RelToSqlConverter.

Method Details

dispatch

protected SqlImplementor.Result dispatch(RelNode e)

Dispatches a call to the visit(Xxx e) method where Xxx most closely matches the runtime type of the argument.

visitInput

public SqlImplementor.Result visitInput(RelNode parent,
 int i,
 boolean anon,
 boolean ignoreClauses,
 Set<SqlImplementor.Clause> expectedClauses)

Description copied from class: SqlImplementor

Visits the ith input of e, the current relational expression.

Specified by:

visitInput in class SqlImplementor

Parameters:

parent - Current relational expression

i - Ordinal of input within e

anon - Whether to remove trivial aliases such as "EXPR$0"

ignoreClauses - Whether to ignore the expected clauses when deciding whether a sub-query is required

expectedClauses - Set of clauses that we expect the builder that consumes this result will create

Returns:

Result

See Also:

• SqlImplementor.isAnon()

isAnon

protected boolean isAnon()

Description copied from class: SqlImplementor

Returns whether to remove trivial aliases such as "EXPR$0" when converting the current relational expression into a SELECT.

For example, INSERT does not care about field names; we would prefer to generate without the "EXPR$0" alias:

INSERT INTO t1 SELECT x, y + 1 FROM t2

rather than with it:

INSERT INTO t1 SELECT x, y + 1 AS EXPR$0 FROM t2

But JOIN does care about field names; we have to generate the "EXPR$0" alias:

SELECT *
 FROM emp AS e
 JOIN (SELECT x, y + 1 AS EXPR$0) AS d
 ON e.deptno = d.EXPR$0
 

because if we omit "AS EXPR$0" we do not know the field we are joining to, and the following is invalid:

SELECT *
 FROM emp AS e
 JOIN (SELECT x, y + 1) AS d
 ON e.deptno = d.EXPR$0
 

Overrides:

isAnon in class SqlImplementor

result

protected SqlImplementor.Result result(SqlNode node,
 Collection<SqlImplementor.Clause> clauses,
 @Nullable String neededAlias,
 @Nullable RelDataType neededType,
 Map<String,RelDataType> aliases)

Description copied from class: SqlImplementor

Factory method for SqlImplementor.Result.

Call this method rather than creating a Result directly, because sub-classes may override.

Overrides:

result in class SqlImplementor

visit

public SqlImplementor.Result visit(RelNode e)

Visits a RelNode; called by dispatch(org.apache.calcite.rel.RelNode) via reflection.

wrapNestedJoin

protected SqlImplementor.Result wrapNestedJoin(SqlImplementor.Result input,
 RelNode inputRel,
 String outerAlias)

Wraps a nested join into a subquery with explicit column aliases.

This is specifically required for dialects like ClickHouse where the identifier resolver cannot resolve columns with internal table qualifiers (e.g., 'd1.loc') when they are wrapped in a subquery alias. By forcing an explicit 'AS' projection for every column, we ensure the identifiers are flattened and visible to the outer query block.

Parameters:

input - The Result of the nested join branch

inputRel - The RelNode representing the join branch to extract row types

outerAlias - The alias to be assigned to the wrapped subquery

Returns:

A new Result containing the wrapped SQL with explicit aliases

visit

public SqlImplementor.Result visit(Join e)

Visits a Join; called by dispatch(org.apache.calcite.rel.RelNode) via reflection.

visitAntiOrSemiJoin

protected SqlImplementor.Result visitAntiOrSemiJoin(Join e)

visit

public SqlImplementor.Result visit(Correlate e)

Visits a Correlate; called by dispatch(org.apache.calcite.rel.RelNode) via reflection.

visit

public SqlImplementor.Result visit(Filter e)

Visits a Filter; called by dispatch(org.apache.calcite.rel.RelNode) via reflection.

visit

public SqlImplementor.Result visit(Project e)

Visits a Project and converts it to a SqlSelect.

If the project defines correlation variables (e.g., via $cor0), this method ensures that the input relation is assigned a stable alias (either the natural table name or a synthetic alias like 't'). This enables nested correlated subqueries to correctly qualify their column references back to this project's scope.

For simple table scans, it avoids forcing an explicit 'AS' clause to maintain compatibility with DML statements (like UPDATE/DELETE) in certain SQL dialects.

visit

public SqlImplementor.Result visit(Window e)

Visits a Window; called by dispatch(org.apache.calcite.rel.RelNode) via reflection.

visit

public SqlImplementor.Result visit(Aggregate e)

Visits an Aggregate; called by dispatch(org.apache.calcite.rel.RelNode) via reflection.

buildAggGroupList

protected void buildAggGroupList(Aggregate e,
 SqlImplementor.Builder builder,
 List<SqlNode> groupByList,
 List<SqlNode> selectList)

Builds the group list for an Aggregate node.

Parameters:

e - The Aggregate node

builder - The SQL builder

groupByList - output group list

selectList - output select list

buildAggregate

protected SqlImplementor.Builder buildAggregate(Aggregate e,
 SqlImplementor.Builder builder,
 List<SqlNode> selectList,
 List<SqlNode> groupByList)

Builds an aggregate query.

Parameters:

e - The Aggregate node

builder - The SQL builder

selectList - The precomputed group list

groupByList - The precomputed select list

Returns:

The aggregate query result

visit

public SqlImplementor.Result visit(TableScan e)

Visits a TableScan; called by dispatch(org.apache.calcite.rel.RelNode) via reflection.

visit

public SqlImplementor.Result visit(Union e)

Visits a Union; called by dispatch(org.apache.calcite.rel.RelNode) via reflection.

visit

public SqlImplementor.Result visit(Intersect e)

Visits an Intersect; called by dispatch(org.apache.calcite.rel.RelNode) via reflection.

visit

public SqlImplementor.Result visit(Minus e)

Visits a Minus; called by dispatch(org.apache.calcite.rel.RelNode) via reflection.

visit

public SqlImplementor.Result visit(Calc e)

Visits a Calc; called by dispatch(org.apache.calcite.rel.RelNode) via reflection.

visit

public SqlImplementor.Result visit(Values e)

Visits a Values; called by dispatch(org.apache.calcite.rel.RelNode) via reflection.

visit

public SqlImplementor.Result visit(Sample e)

Visits a Sample; called by dispatch(org.apache.calcite.rel.RelNode) via reflection.

visit

public SqlImplementor.Result visit(Sort e)

Visits a Sort; called by dispatch(org.apache.calcite.rel.RelNode) via reflection.

hasTrickyRollup

public boolean hasTrickyRollup(Sort e,
 Aggregate aggregate)

visit

public SqlImplementor.Result visit(TableModify modify)

Visits a TableModify; called by dispatch(org.apache.calcite.rel.RelNode) via reflection.

visit

public SqlImplementor.Result visit(Match e)

Visits a Match; called by dispatch(org.apache.calcite.rel.RelNode) via reflection.

visit

public SqlImplementor.Result visit(Uncollect e)

visit

public SqlImplementor.Result visit(TableFunctionScan e)

createAsFullOperands

public List<SqlNode> createAsFullOperands(RelDataType rowType,
 SqlNode leftOperand,
 String alias)

Creates operands for a full AS operator. Format SqlNode AS alias(col_1, col_2,... ,col_n).

Parameters:

rowType - Row type of the SqlNode

leftOperand - SqlNode

alias - alias

addSelect

public void addSelect(List<SqlNode> selectList,
 SqlNode node,
 RelDataType rowType)

Overrides:

addSelect in class SqlImplementor