/create/projection

URL: http://<db.host>:<db.port>/create/projection

Creates a new projection of an existing table. A projection represents a subset of the columns (potentially including derived columns) of a table.

For projection details and examples, see Projections. For limitations, see Projection Limitations and Cautions.

Window functions, which can perform operations like moving averages, are available through this endpoint as well as /get/records/bycolumn.

A projection can be created with a different shard key than the source table. By specifying shard_key, the projection will be sharded according to the specified columns, regardless of how the source table is sharded. The source table can even be unsharded or replicated.

If input parameter table_name is empty, selection is performed against a single-row virtual table. This can be useful in executing temporal (NOW()), identity (USER()), or constant-based functions (GEODIST(-77.11, 38.88, -71.06, 42.36)).

Input Parameter Description

Name

Type

Description

table_name

string

Name of the existing table on which the projection is to be applied, in [schema_name.]table_name format, using standard name resolution rules. An empty table name creates a projection from a single-row virtual table, where columns specified should be constants or constant expressions.

projection_name

string

Name of the projection to be created, in [schema_name.]table_name format, using standard name resolution rules and meeting table naming criteria.

column_names

array of strings

List of columns from input parameter table_name to be included in the projection. Can include derived columns. Can be specified as aliased via the syntax 'column_name as alias'.

options

map of string to strings

Optional parameters. The default value is an empty map ( {} ).

Supported Parameters (keys)

Parameter Description

create_temp_table

If true, a unique temporary table name will be generated in the sys_temp schema and used in place of input parameter projection_name. If persist is false (or unspecified), then this is always allowed even if the caller does not have permission to create tables. The generated name is returned in qualified_projection_name. The default value is false. The supported values are:

true
false

collection_name

[DEPRECATED--please specify the containing schema for the projection as part of input parameter projection_name and use /create/schema to create the schema if non-existent] Name of a schema for the projection. If the schema is non-existent, it will be automatically created. The default value is ''.

expression

An optional filter expression to be applied to the source table prior to the projection. The default value is ''.

is_replicated

If true then the projection will be replicated even if the source table is not. The default value is false. The supported values are:

true
false

offset

The number of initial results to skip (this can be useful for paging through the results). The default value is '0'.

limit

The number of records to keep. The default value is '-9999'.

order_by

Comma-separated list of the columns to be sorted by; e.g. 'timestamp asc, x desc'. The columns specified must be present in input parameter column_names. If any alias is given for any column name, the alias must be used, rather than the original column name. The default value is ''.

chunk_size

Indicates the number of records per chunk to be used for this projection.

chunk_column_max_memory

Indicates the target maximum data size for each column in a chunk to be used for this projection.

chunk_max_memory

Indicates the target maximum data size for all columns in a chunk to be used for this projection.

create_indexes

Comma-separated list of columns on which to create indexes on the projection. The columns specified must be present in input parameter column_names. If any alias is given for any column name, the alias must be used, rather than the original column name.

ttl

Sets the TTL of the projection specified in input parameter projection_name.

shard_key

Comma-separated list of the columns to be sharded on; e.g. 'column1, column2'. The columns specified must be present in input parameter column_names. If any alias is given for any column name, the alias must be used, rather than the original column name. The default value is ''.

persist

If true, then the projection specified in input parameter projection_name will be persisted and will not expire unless a ttl is specified. If false, then the projection will be an in-memory table and will expire unless a ttl is specified otherwise. The default value is false. The supported values are:

true
false

preserve_dict_encoding

If true, then columns that were dict encoded in the source table will be dict encoded in the projection. The default value is true. The supported values are:

true
false

retain_partitions

Determines whether the created projection will retain the partitioning scheme from the source table. The default value is false. The supported values are:

true
false

partition_type

Partitioning scheme to use.

Supported Values	Description
RANGE	Use range partitioning.
INTERVAL	Use interval partitioning.
LIST	Use list partitioning.
HASH	Use hash partitioning.
SERIES	Use series partitioning.

partition_keys

Comma-separated list of partition keys, which are the columns or column expressions by which records will be assigned to partitions defined by partition_definitions.

partition_definitions

Comma-separated list of partition definitions, whose format depends on the choice of partition_type. See range partitioning, interval partitioning, list partitioning, hash partitioning, or series partitioning for example formats.

is_automatic_partition

If true, a new partition will be created for values which don't fall into an existing partition. Currently only supported for list partitions. The default value is false. The supported values are:

true
false

view_id

ID of view of which this projection is a member. The default value is ''.

strategy_definition

The tier strategy for the table and its columns.

join_window_functions

If set, window functions which require a reshard will be computed separately and joined back together, if the width of the projection is greater than the join_window_functions_threshold. The default value is 'true'.

join_window_functions_threshold

If the projection is greater than this width (in bytes), then window functions which require a reshard will be computed separately and joined back together. The default value is ''.

Output Parameter Description

The GPUdb server embeds the endpoint response inside a standard response structure which contains status information and the actual response to the query. Here is a description of the various fields of the wrapper:

Name

Type

Description

status

String

'OK' or 'ERROR'

message

String

Empty if success or an error message

data_type

String

'create_projection_response' or 'none' in case of an error

data

String

Empty string

data_str

JSON or String

This embedded JSON represents the result of the /create/projection endpoint:

Name

Type

Description

projection_name

string

Value of input parameter projection_name.

info

map of string to strings

Additional information. The default value is an empty map ( {} ).

Possible Parameters (keys)	Parameter Description
count	Number of records in the final table
qualified_projection_name	The fully qualified name of the projection (i.e. including the schema).

Empty string in case of an error.