Improve Redshift #15365
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| # Redshift Connector | ||
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| To run the Redshift tests you will need to provision a Redshift cluster. The | ||
| tests are designed to run on the smallest possible Redshift cluster containing | ||
| is a single dc2.large instance. Additionally, you will need a S3 bucket | ||
| containing TPCH tiny data in Parquet format. The files should be named: | ||
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| ``` | ||
| s3://<your_bucket>/tpch/tiny/<table_name>.parquet | ||
| ``` | ||
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| To run the tests set the following system properties: | ||
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| ``` | ||
| test.redshift.jdbc.endpoint=<your_endpoint>.<your_region>.redshift.amazonaws.com:5439/ | ||
| test.redshift.jdbc.user=<username> | ||
| test.redshift.jdbc.password=<password> | ||
| test.redshift.s3.tpch.tables.root=<your_bucket> | ||
| test.redshift.iam.role=<your_iam_arm_to_access_bucket> | ||
| ``` |
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| /* | ||
| * Licensed under the Apache License, Version 2.0 (the "License"); | ||
| * you may not use this file except in compliance with the License. | ||
| * You may obtain a copy of the License at | ||
| * | ||
| * http://www.apache.org/licenses/LICENSE-2.0 | ||
| * | ||
| * Unless required by applicable law or agreed to in writing, software | ||
| * distributed under the License is distributed on an "AS IS" BASIS, | ||
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
| * See the License for the specific language governing permissions and | ||
| * limitations under the License. | ||
| */ | ||
| package io.trino.plugin.redshift; | ||
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| import io.trino.plugin.jdbc.aggregation.BaseImplementAvgBigint; | ||
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| public class ImplementRedshiftAvgBigint | ||
| extends BaseImplementAvgBigint | ||
| { | ||
| @Override | ||
| protected String getRewriteFormatExpression() | ||
| { | ||
| return "avg(CAST(%s AS double precision))"; | ||
| } | ||
| } |
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| /* | ||
| * Licensed under the Apache License, Version 2.0 (the "License"); | ||
| * you may not use this file except in compliance with the License. | ||
| * You may obtain a copy of the License at | ||
| * | ||
| * http://www.apache.org/licenses/LICENSE-2.0 | ||
| * | ||
| * Unless required by applicable law or agreed to in writing, software | ||
| * distributed under the License is distributed on an "AS IS" BASIS, | ||
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
| * See the License for the specific language governing permissions and | ||
| * limitations under the License. | ||
| */ | ||
| package io.trino.plugin.redshift; | ||
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| import io.trino.matching.Capture; | ||
| import io.trino.matching.Captures; | ||
| import io.trino.matching.Pattern; | ||
| import io.trino.plugin.base.aggregation.AggregateFunctionRule; | ||
| import io.trino.plugin.jdbc.JdbcColumnHandle; | ||
| import io.trino.plugin.jdbc.JdbcExpression; | ||
| import io.trino.spi.connector.AggregateFunction; | ||
| import io.trino.spi.expression.Variable; | ||
| import io.trino.spi.type.DecimalType; | ||
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| import java.util.Optional; | ||
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| import static com.google.common.base.Verify.verify; | ||
| import static io.trino.matching.Capture.newCapture; | ||
| import static io.trino.plugin.base.aggregation.AggregateFunctionPatterns.basicAggregation; | ||
| import static io.trino.plugin.base.aggregation.AggregateFunctionPatterns.functionName; | ||
| import static io.trino.plugin.base.aggregation.AggregateFunctionPatterns.singleArgument; | ||
| import static io.trino.plugin.base.expression.ConnectorExpressionPatterns.type; | ||
| import static io.trino.plugin.base.expression.ConnectorExpressionPatterns.variable; | ||
| import static io.trino.plugin.redshift.RedshiftClient.REDSHIFT_MAX_DECIMAL_PRECISION; | ||
| import static java.lang.String.format; | ||
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| public class ImplementRedshiftAvgDecimal | ||
| implements AggregateFunctionRule<JdbcExpression, String> | ||
| { | ||
| private static final Capture<Variable> INPUT = newCapture(); | ||
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| @Override | ||
| public Pattern<AggregateFunction> getPattern() | ||
| { | ||
| return basicAggregation() | ||
| .with(functionName().equalTo("avg")) | ||
| .with(singleArgument().matching( | ||
| variable() | ||
| .with(type().matching(DecimalType.class::isInstance)) | ||
| .capturedAs(INPUT))); | ||
| } | ||
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| @Override | ||
| public Optional<JdbcExpression> rewrite(AggregateFunction aggregateFunction, Captures captures, RewriteContext<String> context) | ||
| { | ||
| Variable input = captures.get(INPUT); | ||
| JdbcColumnHandle columnHandle = (JdbcColumnHandle) context.getAssignment(input.getName()); | ||
| DecimalType type = (DecimalType) columnHandle.getColumnType(); | ||
| verify(aggregateFunction.getOutputType().equals(type)); | ||
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| // When decimal type has maximum precision we can get result that is not matching Presto avg semantics. | ||
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| if (type.getPrecision() == REDSHIFT_MAX_DECIMAL_PRECISION) { | ||
| return Optional.of(new JdbcExpression( | ||
| format("avg(CAST(%s AS decimal(%s, %s)))", context.rewriteExpression(input).orElseThrow(), type.getPrecision(), type.getScale()), | ||
| columnHandle.getJdbcTypeHandle())); | ||
| } | ||
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| // Redshift avg function rounds down resulting decimal. | ||
| // To match Presto avg semantics, we extend scale by 1 and round result to target scale. | ||
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| return Optional.of(new JdbcExpression( | ||
| format("round(avg(CAST(%s AS decimal(%s, %s))), %s)", context.rewriteExpression(input).orElseThrow(), type.getPrecision() + 1, type.getScale() + 1, type.getScale()), | ||
| columnHandle.getJdbcTypeHandle())); | ||
| } | ||
| } | ||
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This change is backward incompatible change. It is changing semantics of Redshift connector. One could say that after this change it is a new different Redshift connector. Most of the existing production usages of Redshift will now require a migration to make Trino upgrade. Such migration is a binary step. Either user is adjusted to use 403 Redshift connector or 404. There is no middle ground, so rolling back such migration is also difficult.
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Let's restore old one as
redshift-legacy?There was a problem hiding this comment.
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I am not sure if it is enough. I would prefer to rename the existing one to mark it is deprecated (legacy) and create a new one with unique name (
redshift-v2?). Then after some time once legacy is removed I would rename the one toredshift)