[CALCITE-222] User-defined table macros

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Labels: github-import
• Assignee: Unassigned
• Reporter: GitHub Import
• Created: 18/Jun/14 08:40
• Updated: 05/Sep/19 03:09
• Resolved: 18/Jun/14 08:40

Description

A table macro is a function that gets executed at prepare time and that generates a relational expression. It can have arguments, as long as those arguments are constants. Views are a special case of table macros - they have no arguments, so can be invoked using the same syntax as regular tables.

Table macros can be registered programmatically, using `Schema.add(String name, Function function)`, where function implements `TableMacro`.

Or they can be declared in the schema, using a class that has an `eval` method (static or non-static) declared to return `Table` or a subclass, and that actually return an object that implements `TranslatableTable`. Like this:

```json
{
version: '1.0',
schemas: [
{
name: 'ADHOC',
functions: [

{ name: 'MAC', className: 'com.example.MyTableMacro' }

]
}
]
}
```

```java
public class MyTableMacro {
public Table eval(String s) {
return new TranslatableTable()

{ ... }

;
}
}
```

```sql
SELECT * FROM TABLE(adhoc.mac('a string'));
```

---------------- Imported from GitHub ----------------
Url: https://github.com/julianhyde/optiq/issues/222
Created by: julianhyde
Labels:
Created at: Wed Apr 02 08:15:22 CEST 2014
State: closed