org.apache.calcite.model.JsonView Maven / Gradle / Ivy
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/*
* 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.model;
import java.util.List;
/**
* View schema element.
*
* Like base class {@link JsonTable},
* occurs within {@link JsonMapSchema#tables}.
*
*
Modifiable views
*
* A view is modifiable if contains only SELECT, FROM, WHERE (no JOIN,
* aggregation or sub-queries) and every column:
*
*
* - is specified once in the SELECT clause; or
*
- occurs in the WHERE clause with a column = literal predicate; or
*
- is nullable.
*
*
* The second clause allows Calcite to automatically provide the correct
* value for hidden columns. It is useful in, say, a multi-tenant environment,
* where the {@code tenantId} column is hidden, mandatory (NOT NULL), and has a
* constant value for a particular view.
*
*
Errors regarding modifiable views:
*
*
* - If a view is marked modifiable: true and is not modifiable, Calcite
* throws an error while reading the schema.
*
- If you submit an INSERT, UPDATE or UPSERT command to a non-modifiable
* view, Calcite throws an error when validating the statement.
*
- If a DML statement creates a row that would not appear in the view
* (for example, a row in female_emps, above, with gender = 'M'), Calcite
* throws an error when executing the statement.
*
*
* @see JsonRoot Description of schema elements
*/
public class JsonView extends JsonTable {
/** SQL query that is the definition of the view.
*
* Must be a string or a list of strings (which are concatenated into a
* multi-line SQL string, separated by newlines).
*/
public Object sql;
/** Schema name(s) to use when resolving query.
*
*
If not specified, defaults to current schema.
*/
public List path;
/** Whether this view should allow INSERT requests.
*
* The values have the following meanings:
*
* - If true, Calcite throws an error when validating the schema if the
* view is not modifiable.
*
- If null, Calcite deduces whether the view is modifiable.
*
- If false, Calcite will not allow inserts.
*
*
* The default value is {@code null}.
*/
public Boolean modifiable;
public void accept(ModelHandler handler) {
handler.visit(this);
}
@Override public String toString() {
return "JsonView(name=" + name + ")";
}
/** Returns the SQL query as a string, concatenating a list of lines if
* necessary. */
public String getSql() {
return JsonLattice.toString(sql);
}
}
// End JsonView.java