org.apache.calcite.DataContext Maven / Gradle / Ivy
Go to download
Show more of this group Show more artifacts with this name
Show all versions of calcite-core Show documentation
Show all versions of calcite-core Show documentation
Core Calcite APIs and engine.
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to you 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 org.apache.calcite;
import org.apache.calcite.adapter.java.JavaTypeFactory;
import org.apache.calcite.linq4j.QueryProvider;
import org.apache.calcite.linq4j.tree.Expressions;
import org.apache.calcite.linq4j.tree.ParameterExpression;
import org.apache.calcite.schema.SchemaPlus;
import org.apache.calcite.sql.advise.SqlAdvisor;
import com.google.common.base.CaseFormat;
import java.io.InputStream;
import java.io.OutputStream;
import java.lang.reflect.Modifier;
import java.util.Locale;
import java.util.TimeZone;
import java.util.concurrent.atomic.AtomicBoolean;
/**
* Runtime context allowing access to the tables in a database.
*/
public interface DataContext {
ParameterExpression ROOT =
Expressions.parameter(Modifier.FINAL, DataContext.class, "root");
/**
* Returns a sub-schema with a given name, or null.
*/
SchemaPlus getRootSchema();
/**
* Returns the type factory.
*/
JavaTypeFactory getTypeFactory();
/**
* Returns the query provider.
*/
QueryProvider getQueryProvider();
/**
* Returns a context variable.
*
* Supported variables include: "sparkContext", "currentTimestamp",
* "localTimestamp".
*
* @param name Name of variable
*/
Object get(String name);
/** Variable that may be asked for in a call to {@link DataContext#get}. */
enum Variable {
UTC_TIMESTAMP("utcTimestamp", Long.class),
/** The time at which the current statement started executing. In
* milliseconds after 1970-01-01 00:00:00, UTC. Required. */
CURRENT_TIMESTAMP("currentTimestamp", Long.class),
/** The time at which the current statement started executing. In
* milliseconds after 1970-01-01 00:00:00, in the time zone of the current
* statement. Required. */
LOCAL_TIMESTAMP("localTimestamp", Long.class),
/** The Spark engine. Available if Spark is on the class path. */
SPARK_CONTEXT("sparkContext", Object.class),
/** A mutable flag that indicates whether user has requested that the
* current statement be canceled. Cancellation may not be immediate, but
* implementations of relational operators should check the flag fairly
* frequently and cease execution (e.g. by returning end of data). */
CANCEL_FLAG("cancelFlag", AtomicBoolean.class),
/** Query timeout in milliseconds.
* When no timeout is set, the value is 0 or not present. */
TIMEOUT("timeout", Long.class),
/** Advisor that suggests completion hints for SQL statements. */
SQL_ADVISOR("sqlAdvisor", SqlAdvisor.class),
/** Writer to the standard error (stderr). */
STDERR("stderr", OutputStream.class),
/** Reader on the standard input (stdin). */
STDIN("stdin", InputStream.class),
/** Writer to the standard output (stdout). */
STDOUT("stdout", OutputStream.class),
/** Locale in which the current statement is executing.
* Affects the behavior of functions such as {@code DAYNAME} and
* {@code MONTHNAME}. Required; defaults to the root locale if the
* connection does not specify a locale. */
LOCALE("locale", Locale.class),
/** Time zone in which the current statement is executing. Required;
* defaults to the time zone of the JVM if the connection does not specify a
* time zone. */
TIME_ZONE("timeZone", TimeZone.class),
/** The query user.
*
* Default value is "sa". */
USER("user", String.class),
/** The system user.
*
*
Default value is "user.name" from
* {@link System#getProperty(String)}. */
SYSTEM_USER("systemUser", String.class);
public final String camelName;
public final Class clazz;
Variable(String camelName, Class clazz) {
this.camelName = camelName;
this.clazz = clazz;
assert camelName.equals(
CaseFormat.UPPER_UNDERSCORE.to(CaseFormat.LOWER_CAMEL, name()));
}
/** Returns the value of this variable in a given data context. */
public T get(DataContext dataContext) {
//noinspection unchecked
return (T) clazz.cast(dataContext.get(camelName));
}
}
}
// End DataContext.java