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[Coral-Trino] Cast char fields, if necessary, to varchar type in the …
…set operation In case of dealing with Hive views which make use of set operation (e.g. UNION) ensure that the `char` fields from the inner SELECT statements have the same type as the output field types of the set operation. Due to wrong coercion between `varchar` and `char` in Trino, as described in trinodb/trino#9031 , a work-around needs to be applied in case of translating Hive views which contain a UNION dealing with char and varchar types. The work-around consists in the explicit cast of the field having char type towards varchar type corresponding of the set operation output type.
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165
...rc/main/java/com/linkedin/coral/trino/rel2trino/transformers/UnionSqlCallTransformer.java
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| /** | ||
| * Copyright 2023 LinkedIn Corporation. All rights reserved. | ||
| * Licensed under the BSD-2 Clause license. | ||
| * See LICENSE in the project root for license information. | ||
| */ | ||
| package com.linkedin.coral.trino.rel2trino.transformers; | ||
|
|
||
| import java.util.ArrayList; | ||
| import java.util.List; | ||
| import java.util.Optional; | ||
| import java.util.stream.Collectors; | ||
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|
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| import org.apache.calcite.rel.type.RelDataType; | ||
| import org.apache.calcite.sql.SqlBasicTypeNameSpec; | ||
| import org.apache.calcite.sql.SqlCall; | ||
| import org.apache.calcite.sql.SqlCallBinding; | ||
| import org.apache.calcite.sql.SqlDataTypeSpec; | ||
| import org.apache.calcite.sql.SqlIdentifier; | ||
| import org.apache.calcite.sql.SqlKind; | ||
| import org.apache.calcite.sql.SqlNode; | ||
| import org.apache.calcite.sql.SqlNodeList; | ||
| import org.apache.calcite.sql.SqlSelect; | ||
| import org.apache.calcite.sql.SqlTypeNameSpec; | ||
| import org.apache.calcite.sql.fun.SqlCastFunction; | ||
| import org.apache.calcite.sql.fun.SqlStdOperatorTable; | ||
| import org.apache.calcite.sql.parser.SqlParserPos; | ||
| import org.apache.calcite.sql.type.SqlTypeName; | ||
| import org.apache.calcite.sql.validate.SqlValidator; | ||
| import org.apache.calcite.sql.validate.SqlValidatorScope; | ||
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|
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| import com.linkedin.coral.common.transformers.SqlCallTransformer; | ||
| import com.linkedin.coral.common.utils.TypeDerivationUtil; | ||
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| import static org.apache.calcite.rel.rel2sql.SqlImplementor.POS; | ||
| import static org.apache.calcite.sql.parser.SqlParserPos.ZERO; | ||
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| /** | ||
| * This transformer class is used to adapt expressions in | ||
| * set statements (e.g.: `UNION`, `INTERSECT`, `MINUS`) | ||
| * in case that the branches of the set statement contain fields in | ||
| * char family which have different types. | ||
| * The `char` fields which are differing from the expected `varchar` output | ||
| * of the set statement will be adapted through an explicit `CAST` to the `varchar` type. | ||
| * | ||
| * @see <a href="https://github.com/trinodb/trino/issues/9031">Change char/varchar coercion in Trino</a> | ||
| */ | ||
| public class UnionSqlCallTransformer extends SqlCallTransformer { | ||
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| public UnionSqlCallTransformer(TypeDerivationUtil typeDerivationUtil) { | ||
| super(typeDerivationUtil); | ||
| } | ||
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| @Override | ||
| protected boolean condition(SqlCall sqlCall) { | ||
| return sqlCall.getOperator().kind == SqlKind.UNION || sqlCall.getOperator().kind == SqlKind.INTERSECT | ||
| || sqlCall.getOperator().kind == SqlKind.MINUS; | ||
| } | ||
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| @Override | ||
| protected SqlCall transform(SqlCall sqlCall) { | ||
| List<SqlNode> operandsList = sqlCall.getOperandList(); | ||
| List<List<Optional<RelDataType>>> columnsTypesLists = new ArrayList<>(); | ||
| for (SqlNode operand : operandsList) { | ||
| if (operand.getKind() == SqlKind.SELECT && ((SqlSelect) operand).getSelectList() != null) { | ||
| SqlSelect select = (SqlSelect) operand; | ||
| List<SqlNode> selectNodes = select.getSelectList().getList(); | ||
| if (columnsTypesLists.isEmpty()) { | ||
| for (int i = 0; i < selectNodes.size(); i++) { | ||
| columnsTypesLists.add(new ArrayList<>()); | ||
| } | ||
| } | ||
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| for (int i = 0; i < selectNodes.size(); i++) { | ||
| SqlNode sqlNode = selectNodes.get(i); | ||
| if (sqlNode.getKind() == SqlKind.IDENTIFIER && ((SqlIdentifier) sqlNode).isStar()) { | ||
| // The type derivation of * on the SqlNode layer is not supported now. | ||
| return sqlCall; | ||
| } | ||
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| Optional<RelDataType> selectNodeDataType; | ||
| try { | ||
| selectNodeDataType = Optional.of(deriveRelDatatype(sqlNode)); | ||
| } catch (RuntimeException e) { | ||
| // The type derivation may fail for complex expressions | ||
| selectNodeDataType = Optional.empty(); | ||
| } | ||
| columnsTypesLists.get(i).add(selectNodeDataType); | ||
| } | ||
| } else { | ||
| return sqlCall; | ||
| } | ||
| } | ||
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| List<SqlNode> updatedOperands = new ArrayList<>(sqlCall.getOperandList().size()); | ||
| for (SqlNode operand : operandsList) { | ||
| SqlSelect select = (SqlSelect) operand; | ||
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| List<SqlNode> selectNodes = select.getSelectList().getList(); | ||
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| List<SqlNode> rewrittenSelectNodes = new ArrayList<>(); | ||
| boolean useRewrittenSelectNodes = false; | ||
| for (int i = 0; i < selectNodes.size(); i++) { | ||
|
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| if (columnsTypesLists.get(i).stream().anyMatch(columnType -> !columnType.isPresent())) { | ||
| // Couldn't determine the type for all the expressions | ||
| continue; | ||
| } | ||
| RelDataType inferredColumnType = | ||
| leastRestrictive(columnsTypesLists.get(i).stream().map(Optional::get).collect(Collectors.toList())); | ||
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| SqlNode selectNode = selectNodes.get(i); | ||
| RelDataType selectNodeDataType = deriveRelDatatype(selectNodes.get(i)); | ||
| if (!selectNodeDataType.equals(inferredColumnType) && selectNodeDataType.getSqlTypeName() == SqlTypeName.CHAR | ||
| && inferredColumnType.getSqlTypeName() == SqlTypeName.VARCHAR) { | ||
| // Work-around for the Trino limitation in dealing UNION statements between `char` and `varchar`. | ||
| // See https://github.com/trinodb/trino/issues/9031 | ||
| SqlNode rewrittenSelectNode = castNode(selectNode, inferredColumnType); | ||
| if (!useRewrittenSelectNodes) { | ||
| rewrittenSelectNodes.addAll(selectNodes.subList(0, i)); | ||
| useRewrittenSelectNodes = true; | ||
| } | ||
| rewrittenSelectNodes.add(rewrittenSelectNode); | ||
| } else if (useRewrittenSelectNodes) { | ||
| rewrittenSelectNodes.add(selectNode); | ||
| } | ||
| } | ||
|
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| if (useRewrittenSelectNodes) { | ||
| select.setSelectList(new SqlNodeList(rewrittenSelectNodes, SqlParserPos.ZERO)); | ||
| } | ||
| updatedOperands.add(operand); | ||
| } | ||
| return sqlCall.getOperator().createCall(POS, updatedOperands); | ||
| } | ||
|
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| private SqlNode castNode(SqlNode node, RelDataType type) { | ||
| if (node.getKind() == SqlKind.AS) { | ||
| SqlNode expression = ((SqlCall) node).getOperandList().get(0); | ||
| SqlIdentifier identifier = (SqlIdentifier) ((SqlCall) node).getOperandList().get(1); | ||
| return SqlStdOperatorTable.AS.createCall(POS, new SqlCastFunction() { | ||
| @Override | ||
| public RelDataType deriveType(SqlValidator validator, SqlValidatorScope scope, SqlCall call) { | ||
| SqlCallBinding opBinding = new SqlCallBinding(validator, scope, call); | ||
| return inferReturnType(opBinding); | ||
| } | ||
| }.createCall(ZERO, expression, getSqlDataTypeSpecForCasting(type)), identifier); | ||
| } else { | ||
| // If there's no existing alias, just do the cast | ||
| return new SqlCastFunction() { | ||
| @Override | ||
| public RelDataType deriveType(SqlValidator validator, SqlValidatorScope scope, SqlCall call) { | ||
| SqlCallBinding opBinding = new SqlCallBinding(validator, scope, call); | ||
| return inferReturnType(opBinding); | ||
| } | ||
| }.createCall(ZERO, node, getSqlDataTypeSpecForCasting(type)); | ||
| } | ||
| } | ||
|
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| private static SqlDataTypeSpec getSqlDataTypeSpecForCasting(RelDataType relDataType) { | ||
| final SqlTypeNameSpec typeNameSpec = new SqlBasicTypeNameSpec(relDataType.getSqlTypeName(), | ||
| relDataType.getPrecision(), relDataType.getScale(), null, ZERO); | ||
| return new SqlDataTypeSpec(typeNameSpec, ZERO); | ||
| } | ||
| } |
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