Ophidia Operators Manual

The links below give an exhaustive description of all the operators available in the platform. Each manual page describes the operator’s behaviour, its parameters and a simple usage example. A table summarizing the parameters constraints (data type, mandatoriness, admissible and default values) closes each section. To better understand how to submit a request, we recommend you to read the Ophidia Terminal: basic usage guide.


In order to fully use all the Ophidia operators and other features, in dynamic cluster mode, a cluster of I/O server instances must be deployed before running the data operators (e.g. OPH_AGGREGATE, OPH_REDUCE, etc.). A cluster consists of a set of reserved analytics nodes with a single I/O server instance running on each. It is identified by a user-defined host partition name and multiple clusters can be deployed by the same user. After its creation, the user can exploit the computing resources of the cluster by simply specifying the host partition name in the data import operators (OPH_IMPORTNC2, OPH_RANDCUBE2, etc.) and release them at the end of its workflow of operators by undeploying the cluster. Additional information about the usage of cluster management can be found in the I/O server cluster guides.

Data Analysis

This group includes the main data processing Ophidia operators. Most of them process an input cube to obtain another cube with different data and/or metadata.

The operators OPH_INTERCUBE, OPH_MERGECUBES and OPH_MERGECUBES2 process two input cubes.

The operator OPH_SCRIPT allows the user to run a generic (pre-registered) bash script.

Data reduction can be applied to dimension values (and the corresponding measures) in two ways:

  • by group size
  • by concept hiearchy level

The former approach is adopted by the operators OPH_AGGREGATE, for tuples, and OPH_REDUCE, for arrays. Use group_size to set the number of elements to be aggregated. The latter approach is adopted by the operators OPH_AGGREGATE2, for explicit dimensions, and OPH_REDUCE2, for implicit dimensions. See Time Management section for more information about concept levels and aggregation.

OPH_AGGREGATE It executes an aggregation function on a datacube with respect to explicit dimensions.
OPH_AGGREGATE2 It executes an aggregation operation based on hierarchy on a datacube along an explicit dimension.
OPH_APPLY It executes a query on a datacube.
OPH_DRILLDOWN It performs a drill-down operation on a datacube, i.e. it transforms dimensions from implicit to explicit.
OPH_DUPLICATE It duplicates a datacube creating an exact copy of the input one.
OPH_INTERCUBE It executes an operation between two datacubes with the same fragmentation structure and returns a new datacube as result of the specified operation.
OPH_MERGE It creates a new datacube grouping nmerge input fragments in a new output fragment.
OPH_MERGECUBES It merges the measures of n input datacubes with the same fragmentation structure and creates a new datacube with the union of the n measures.
OPH_MERGECUBES2 It merges the measures of n input datacubes with the same fragmentation structure and creates a new datacube with the union of the n measures. A new implicit dimension will be created.
OPH_PERMUTE It performs a permutation of the dimensions of a datacube.
OPH_REDUCE It performs a reduction operation on a datacube with respect to implicit dimensions.
OPH_REDUCE2 It performs a reduction operation based on hierarchy on a datacube along an implicit dimension.
OPH_ROLLUP It performs a roll-up operation on a datacube, i.e. it transforms dimensions from explicit to implicit.
OPH_SCRIPT It executes a bash script.
OPH_SPLIT It creates a new datacube by splitting input fragments in nsplit output fragments in the same origin database.
OPH_SUBSET It performs a subsetting operation along dimensions of a datacube.
OPH_SUBSET2 It performs a subsetting operation along dimensions of a datacube (DEPRECATED).

Data Import/Export

These operators translate the format of a dataset, retrieved from an external source (e.g. an OPeNDAP service) or stored in a local data repository (see configuration notes for futher details), into the format used by Ophidia and vice versa. To get a more advanced understanding about the Ophidia format and how to manage data organization and distribution have a look at the data model section.

The following translations are supported:

FROM TO Operator
OPH_B2DROP It uploads a file onto a B2DROP remote folder.
OPH_CONCATNC It concatenates a NetCDF file to a datacube.
OPH_CONCATNC2 It concatenates a NetCDF file to a datacube (Ophidia I/O Server-based version).
OPH_EXPLORECUBE It prints the data stored into a datacube, possibly subset along its dimensions.
OPH_EXPLORENC It read a NetCDF file (both measure and dimensions).
OPH_EXPORTNC It exports data of a datacube into multiple NetCDF files.
OPH_EXPORTNC2 It exports data of a datacube into a single NetCDF files (parallel version).
OPH_IMPORTFITS It imports a FITS file into a datacube.
OPH_IMPORTNC It imports a NetCDF file into a datacube.
OPH_IMPORTNC2 It imports a NetCDF file into a datacube (Ophidia I/O Server-based version).
OPH_PUBLISH It creates HTML pages with data and other information from a datacube.
OPH_RANDCUBE It creates a new datacube with random data and dimensions.
OPH_RANDCUBE2 It creates a new datacube with random data and dimensions (Ophidia I/O Server-based version).
OPH_UNPUBLISH It removes the HTML pages created by the PUBLISH2 operator.


Metadata operators are used to print information about datacubes: size, provenance, dimension values, attributes, physical organization of data, etc.

OPH_CONTAINERSCHEMA It shows some information about a container: description, vocabulary, dimension list, etc.
OPH_CUBEELEMENTS It computes and displays the number of elements stored in the input datacube.
OPH_CUBEIO It shows the hierarchy of all datacubes used to generate the input datacube and of those derived from it.
OPH_CUBESCHEMA It shows metadata information about a datacube and the dimensions related to it.
OPH_CUBESIZE It computes and displays the size of the input datacube.
OPH_METADATA It provides CRUD operations (Create, Read, Update and Delete) on OphidiaDB metadata.
OPH_SEARCH It provides enhanced searching on metadata.
OPH_SHOWGRID It shows information about one or more grids related to the specified container.
OPH_TASKS It shows information about executed tasks.

Virtual File System

These operators allows the user to browse the Ophidia Virtual File System.

OPH_CREATECONTAINER It creates an empty container.
OPH_DELETE It removes a datacube.
OPH_DELETECONTAINER It removes an empty container with related dimensions and grids.
OPH_FOLDER It manages folders of the Ophidia filesystem: creation and removal.
OPH_LIST It shows information about folders, container and datacubes fragmentation (file system).
OPH_MOVECONTAINER It moves/renames a visible container.

Workflow Management

This group includes a number of flow control operators that could be used within an Ophidia workflow to implement complex data processing in batch mode. In particular, they implement several advanced features: setting of run-time variables, iterative and parallel interface, selection interface, interactive workflows, interleaving workflows, etc.

OPH_ELSE Start the last sub-block of a selection block “if”.
OPH_ELSEIF Start a new sub-block of a selection block “if”.
OPH_ENDFOR Close a loop “for”.
OPH_ENDIF Close a selection block “if”.
OPH_FOR Implement a loop “for”.
OPH_IF Open a “if” selection block.
OPH_INPUT It sends commands or data to an interactive task.
OPH_SET Set a parameter in the workflow environment.
OPH_WAIT Wait until an event occurs.


This group consists of operators that allows the user to monitor or stop running workflows (e.g. check for task status), list submitted tasks, get the service parameters to configure automatically the terminal, list or remove sessions (see Session management), grant access permissions to sessions, manager cluster deployment (if enabled), etc.

The operators OPH_LOG_INFO and OPH_SERVICE allows to administrators to read logs and to start/stop Ophidia service.

OPH_CANCEL Stop the execution of a running workflow.
OPH_CLUSTER Start, stop and get information about clusters of I/O servers.
OPH_GET_CONFIG Request the configuration parameters.
OPH_INSTANCES It shows information about host partitions, hosts and dbms instances.
OPH_LOGGINGBK It shows info about jobs and sessions (logging bookkeeping).
OPH_LOG_INFO It reads the last lines from the server log or from a specific container log.
OPH_MANAGE_SESSION Request or set session data: session list, session creation date, authorized users, etc.
OPH_RESUME Request the list of the commands submitted within a session or the output of a command.
OPH_SERVICE Request or set the service status.


OPH_FS It browses the real file system: list files, change working directory, etc.
OPH_HIERARCHY It shows the list of the hierarchies or the description of a specified hierarchy.
OPH_MAN It shows a description of the behaviour of an operator/primitive.
OPH_OPERATORS_LIST It shows the list of all active operators.
OPH_PRIMITIVES_LIST It shows a list with info about active Ophidia Primitives loaded into a specific DBMS instance.