Package org.apache.calcite.model

Class JsonView

java.lang.Object

org.apache.calcite.model.JsonTable

org.apache.calcite.model.JsonView

public class JsonView
extends JsonTable

View schema element.

Like base class JsonTable, occurs within 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 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 Also:

• Description of schema elements

Field Summary

Fields

Modifier and Type	Field	Description
final @Nullable Boolean	modifiable	Whether this view should allow INSERT requests.
final @Nullable List<String>	path	Schema name(s) to use when resolving query.
final Object	sql	SQL query that is the definition of the view.

Fields inherited from class org.apache.calcite.model.JsonTable

columns, name, stream

Constructor Summary

Constructors

Constructor	Description
JsonView(String name, JsonStream stream, Object sql, @Nullable List<String> path, @Nullable Boolean modifiable)

Method Summary

Modifier and Type	Method	Description
void	accept(ModelHandler handler)
String	getSql()	Returns the SQL query as a string, concatenating a list of lines if necessary.
String	toString()

Methods inherited from class java.lang.Object

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

Field Details

sql

public final Object sql

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).

path

public final @Nullable List<String> path

Schema name(s) to use when resolving query.

If not specified, defaults to current schema.

modifiable

public final @Nullable Boolean modifiable

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 null.

Constructor Details

JsonView

public JsonView(String name,
 JsonStream stream,
 Object sql,
 @Nullable List<String> path,
 @Nullable Boolean modifiable)

Method Details

accept

public void accept(ModelHandler handler)

Specified by:

accept in class JsonTable

toString

public String toString()

Overrides:

toString in class Object

getSql

public String getSql()

Returns the SQL query as a string, concatenating a list of lines if necessary.