UDTF projection

Stores newly-loaded data after it is transformed and/or aggregated by user-defined transformation functions (UDTFs).

Stores newly-loaded data after it is transformed and/or aggregated by user-defined transformation functions (UDTFs). For details and examples, see Pre-aggregating UDTF results.

Important

Currently, projections can only reference UDTFs developed in C++.

Syntax

CREATE PROJECTION [ IF NOT EXISTS ] [[database.]schema.]projection
[ (
   { projection-column | grouped-clause
   [ ENCODING encoding-type ]
   [ ACCESSRANK integer ]  }[,...]
) ]
AS { batch-query FROM { prepass-query sq-ref | table [[AS] alias] }
     | prepass-query }

batch-query:

SELECT { table-column | expr-with-table-columns }[,...], batch-udtf(batch-args)
   OVER (PARTITION BATCH BY partition-column-expr[,...])
   [ AS (output-columns) ]

prepass-query:

SELECT { table-column | expr-with-table-columns }[,...], prepass-udtf(prepass-args)
   OVER (PARTITION PREPASS BY partition-column-expr[,...])
   [ AS (output-columns) ] FROM table

Arguments

IF NOT EXISTS

If an object with the same name exists, return without creating the object. If you do not use this directive and the object already exists, Vertica returns with an error message.

The IF NOT EXISTS clause is useful for SQL scripts where you might not know if the object already exists. The ON ERROR STOP directive can be helpful in scripts.

[database.]schema

Schema for this projection and its anchor table. The value must be the same for both. If you specify a database, it must be the current database.

projection

Name of the projection to create, which must conform to Identifiers. It must also be unique among all names of sequences, tables, projections, views, and models within the same schema.

projection-column

The name of a projection column. The list of projection columns must match the SELECT list columns and expressions in number, type, and sequence.

If projection column names are omitted, Vertica uses the anchor table column names specified in the SELECT list.

grouped-clause

See GROUPED clause.

ENCODING encoding-type

The column encoding type, by default set to AUTO.

ACCESSRANK integer

Overrides the default access rank for a column. Use this parameter to increase or decrease the speed at which Vertica accesses a column. For more information, see Overriding Default Column Ranking.

SELECT

Specifies the table data to query:

{table-column | expr-with-table-columns } [ [AS] alias] }[,...]

You can optionally assign an alias to each column expression and reference that alias elsewhere in the SELECT statement.

If you specify projection column names, the two lists of projection columns and table columns/expressions must exactly match in number and order.

batch-udtf(batch-args)

The batch UDTF to invoke each time the following events occur:

Tuple mover mergeout
Queries on the projection
If invoked singly, on data load operations

Important

If the projection definition includes a pre-pass subquery, batch-args must exactly match the pre-pass UDTF output columns, in name and order.

prepass-udtf(prepass-args)

The pre-pass UDTF to invoke on each load operation such as COPY or INSERT.

If specified in a subquery, the pre-pass UDTF returns transformed data to the batch query for further processing. Otherwise, the pre-pass query results are added to projection data storage.

OVER (PARTITION { BATCH | PREPASS } BY partition-column-expr[,...])

Specifies the UDTF type and how to partition the data it returns:

BATCH identifies the UDTF as a batch UDTF.
PREPASS identifies the UDTF as a pre-pass UDTF.

In both cases, the OVER clause specifies partitioning with one or more column expressions from the SELECT list. The first expression is the first column expression in the SELECT list, the second expression is the second column expression in the SELECT list, and so on.

Note

The projection is implicitly segmented and ordered on PARTITION BY columns.

AS output-columns

Optionally names columns that are returned by the UDTF.

If a pre-pass subquery omits this clause, the outer batch query UDTF arguments (batch-args) must reference the column names as they are defined in the pre-pass UDTF.

table[[AS]alias]

The projection's anchor table, optionally qualified by an alias.

sq-results

Subquery result set that is returned to the outer batch UDTF.

Privileges

Non-superusers:

Anchor table owner
CREATE privilege on the schema
EXECUTE privileges on all UDTFs that are referenced by the projection

Examples

See Pre-aggregating UDTF results.