Some FAQs

Answers to some Frequently Asked Questions
 
 

General Questions about the product family

What is Polyhedra?

Polyhedra is a family of relational database management systems with a large degree of common functionality, including the same SQL engine and the same client-server protocols. Polyhedra is designed for use in embedded systems, so it is small and fast, and can be used in applications where regular administration is impractical or impossible.

What was Polyhedra designed for?

Polyhedra was designed to provide a coherent set of development tools for database applications in several specific market areas normally not well served by conventional database vendors (both Object-oriented and Relational). The core Real Time Relational Database (RTRDB) is designed to sit in an Open Systems environment employing TCP/IP and UDP for connections to clients and other database servers.

  • Real Time Data Management - The heart of Polyhedra is a fast memory-resident relational database management system called the rtrdb, that is ideally suited to applications requiring both real-time responses to data changes coupled with the flexibility of modern database technology. Such applications exist in the markets of Process Control and Automation, Telecommunications, Point of Sale, Materials Handling and many others.
     
  • Embedded Systems - As the Polyhedra database is memory resident, it is ideally suited to embedded systems that are often diskless. The Polyhedra database has been successfully employed in several embeded systems running on a variety of target achitectures, including Intel x86 and PowerPC-based systems.
     
  • System Front Ends - The RTRDB is capable of communicating directly and actively with other databases, systems and external devices. This makes it an ideal choice for integrating a lot of disparate data systems together into a single coherent application.
The software contains standards-conforming APIs for those wanting to write client applications in C, C++ or Java, and for use on Windows and Linux/x86 it also has an ODBC driver; on Windows, there is also an OLE DB data Provider. As client applications can be colocated or remote from the database(s) they are using, great flexibility is provided in the organisation of the overall system.

What is different about Polyhedra?

Polyhedra offers significant advantages over traditional DBMS systems:

  • Memory Resident - The Database server for Polyhedra IMDB is entirely memory resident. This provides performance that is significantly greater and more predictable than disk-based alternatives. Independent research shows in-memory databases to be an order of magnitude faster than disk based systems, even where the disk based system is cached into RAM.
    Data is persisted (written to a non-volatile store) by the creation of a journal file. Data be marked as persistent or transient to control whether changes to it are journalled, and an application can ask to be notified of a transaction's completion either after the transaction has committed in main memory, or after the journal record has been written. The timing of the creation of a "snapshot", a checkpoint of the current state of the database, is under the control of the application.
    (The Polyhedra family now also includes Polyhedra FlashLite, where the master copy of the data resides in a file, and there is a configurable cache to allow the database designer to balance performance and memory consumption.)
     
  • Fault Tolerant - Polyhedra can be configured so that servers run in a hot-standby arrangement, so that if the master database fails the standby can immediately take over in milliseconds or less.
     
  • Active Queries - Polyhedra incorporates a unique concept called active queries, which allow connected clients to monitor the database for changes to selected information, in a timely and scaleable fashion. No polling needed!
     
  • Active Database - Polyhedra supports the creation of scripts which are triggered by data changes. By use of these, the database becomes an active component in any application and not just a passive data repository like many others.
     
  • Heterogeneous Client-server Architecture - the separation of the the server (and the data it holds) from the client application code protects the database from rogue code, especially in environments where memory-protection is enabled. The platform-independence (heterogeneity) of the protocol used means that clients can be running on separate machines, using different operating systems and processor types to that on which the database server is running.

When was Polyhedra first released?

The first release of Polyhedra32 IMDB was in 1993; see the history section for more information.

What are in the release kits? How do I install Polyhedra?

A polyhedra release kit has a name such as win32-i386-msvc-08.06.0001.zip, which indicate not only what version of Polyhedra it contains, but also the platform for which it is intended - so here we have an 8.6.1 release kit for Polyhedra32 IMDB, for use on Windows on x86-architecture machines, with libraries suitable for use with the Visual C++ compiler. (By contrast, the file name for the corresponding Polyhedra64 IMDB release kit for use on 64-bit Windows platforms has the name win64-x86_64-msvc-08.06.0001.zip, and the Linux/PowerPC release kit is called linux-powerpc-gcc-08.06.0001.tar.gz.) The version naming scheme follows a standard major.minor.bugfix convention, so 8.0.0 was the first major release after the Polyhedra 7 series, and Polyhedra 8.4.1 was a bug-fix release for Polyhedra 8.4. Typically, a major release indicates a significant change in the functionality necessitating a substantive change in the protocols, file formats or APIs, whereas for a minor release the changes are minimal if you do not use the new functionality introduced by the new release. In all cases, though, the Polyhedra compatibility principles mean that adopting the new release is straightforward, and field-upgrades can almost always be done with zero downtime (if using a fault-tolerant server configuration).

In the case of Windows, the release kit is a ZIP file, whereas for other platforms it will be a .tar.gz file; in each case it contains a compressed directory image, and in essence all that needs to be done is to uncompress it. Thus on Windows, there is no need to alter the Windows registry; assuming a Polyhedra 8.7 release kit for Windows has been unpacked into, say, the C:\poly8.7 you would simply ensure that the PATH environment variable included the directory C:\poly8.7\win32\i386\bin. (This is covered in more detail in the installation guide document, included in the release kits.) The contents of the Polyhedra 8.7 release kits for Windows/x86 have the following structure:

  • poly8.7
    • evaluate.pdf
      a guide to getting started with Polyhedra. The latest version of this manual is available for download here.

    • feature.txt
      a document summarising the features that differ (in their availability) between different editions of Polyhedra.

    • install.pdf
      how to install Polyhedra. The latest version of this manual is available for download here.

    • readme.pdf
      Release notes for this release of Polyhedra, including a brief overview of newly added features, and information about migrating applications to use the new release.

    • version.txt
      a text file containing the version number of the new release.

    • examples
      a directory containing example software. The 'clients' subdirectory contains the source code for several applications that are also supplied in executable form in the release kits; these example applications are described in the evaluation guide, and used in the worked exercises in that document (which you are strongly advised to also follow for yourself, if you are new to Polyhedra). Demo_1 to demo_4 are used by the worked exercises in the evaluation guide, and the other subdirectories contain code illustrating particular Polyhedra features - read the text file in the subdirectory for details.

      • clients
      • demo_1
      • demo_2
      • demo_3
      • demo_4
      • demo_db_db_arb
      • ...
      • template

    • include
      header files for use when compiling your own client applications.

    • win32
      While all the other directories will have exactly the same contents for all the release kits for a particular version of Polyhedra, this directory is specific to the Windows release kits. Release kits for other platforms will have a similar, appropriately named directory with a similar structure: that is, a doc and examples directory, and a subdirectory named after the hardware architecture with a copy of the binary executables and (in a subdirectory named after the compiler toolset) some object modules and libraries suitable for use with the indicated compiler.

      • doc
        This contains text files describing how to compile and link client applications on this platform. It also contains instructions on relinking the main Polyhedra executables, to allow you to supply alternative definitions of certain functions - note that for certain editions of Polyhedra this will not be possible as the release kits omit the libraries you would need to achieve this.

      • examples
        some platform-specific examples.

      • i386
        • bin
          the main Polyhedra executables plus some client applications in executable form,

        • msvc
          • lib
            the libraries you will need to build and run your own client applications. For some editions of Polyhedra, this subdirectory will also include the libraries needed to relink the main Polyhedra executables.
In addition to the main release kits, there are also some supplementary, platform-specific release kits. Thus, for Windows and Linux/x86 we supply an ODBC driver kit that allows you to install the standard Polyhedra ODBC library as a driver for use with an ODBC driver manager. The Polyhedra JDBC driver is also supplied as a supplementary release kit; as it is a type-4 driver written purely in Java, it is platform-independent. The reference manuals are not included in the release kits, but can be obtained individually from here; customers with a support contract can also download the complete reference manual kit as a single ZIP file.


Polyhedra Features

Does Polyhedra support the relational model?

Yes, Polyhedra is relational. It also has some object-oriented features (such as table inheritance), but as far as client applications are concerned, it can be thought of a relational database system that allows queries and updates via its SQL engine.

What data types are supported?

Polyhedra supports 64-bit, 32-bit, 16-bit and 8-bit signed integers; 64-bit and 32-bit floating point values; variable-length character strings (both capped-length and unbounded); unbounded-length byte sequences; booleans; and, datetime (with microsecond resolution).

Does Polyhedra support entity and referential integrity?

In a word, yes.
 
Entity integrity says that record must have the right structure: for example, is a table all records have the same number of columns/attributes, and the value placed in a column is of the right type. Thus, you cannot store a string value or a floating-point value in a cell if the column is flagged as having an integer type. Polyhedra enforces this strictly - though if you put a 64-bit floating value into a cell flagged as holding a 32-bit quantity, for example, some accuracy is lost. Polyhedra also enforces 'not null' and uniqueness contraints - thus it ensures the values in the primary key attributes are check to be not not null, and the value in the primary key column (or the combination of values, if the table has a multi-column primary key) uniquely identify that record. Any operation that breaks entity integrity automatically causes the transaction to be aborted, with a suitable error response to the client that initiated the transaction.
 
Referential integrity says that if a column (or combination of columns) is defined to be a foreign key to a record in another table - or even a record in the same table - then for each row the value(s) in the cell(s) making up the foreign key are either null, or identify a single record in the referenced table. Polyhedra allows foreign keys to be defined, and aborts all transactions that break referential integrity. (However, Polyhedra does not perform cascaded deletes, where the deletion of a record will cause the deletion of all records that reference it.)

Does Polyhedra extend the relational model?

Yes. Firstly, Polyhedra allows the database designer to define a table as being 'derived from' another. So a table y that is derived from table x inherits all the attributes/columns that x has (including the primary key attributes), and can have additional columns.  And of course table x can derive from y (inheriting all its columns, including the columns inherited from x) and add further columns. When table t is added, deriving from y say, it can have additional columns with the same names as columns added in table z, and there are no problems with clashes. From the point of view of the database user, tables x, y, z and t all appear as standard tables, and can be populated, updated and queried via SQL in exactly the same way as normal; no special syntax is required. The main advantage of table inheritance is that it allows a more accurate representation of the real world. Thus, in a process control environment, a digital sensor and an analogue sensor have many things in common but their values are of different types, and an analogue sensor would normally have conversion factors (to convert from raw measurements to engineering limits) and alarm limits; all of this is easy to model with a base table called sensor and derived tables called digital and analogue. 

A second extension from the relational model is to allow columns/attributes to be flagged as 'shared' or 'virtual'. A shared column is one where all records in the table (and derived tables) share the same value. Update the shared value in one record, and the new value appears in all records. The shared value does not take up space in the record; instead, it is stored with the definition of the table in the schema. A virtual attribute is similar - except that derived tables keep their own copy of the value, at each level. Thus, if the sensor table has a virtual attribute called tabletype, it is easy to ensure all analogue sensors show the value ANALOGUE (or ANALOG if you prefer American English!) and digital sensors show the value DIGITAL.

What are active queries?

Polyhedra's active query mechanism provides a way for a client application to monitor record(s) in a Polyhedra database without having to poll. Basically, the client application launches a query almost in the normal way - but instead of the server forgetting about the query once it has been answered, it remembers enough about the query so that it can update the client when the records are changed. This is covered in more detail here.

What is the historian module?

Polyhedra 32 IMDB and Polyhedra 64 IMDB have a historian module that can be configured (by creating records in special control tables in the database) to monitor selected tables, and to capture time-stamped samples either periodically or when the values change. The time-series data is kept in a file that is treated as a large circular buffer, and be queried via SQL. Old samples can be archived before they overwritten, and archive files can be brought back online so that they can be queried. This is covered in more detail here.

Can Polyhedra take advantage of SMP and hyperthreaded computers?

As is common in computing, the answer is a conditional yes!
 
The Polyhedra database server uses multiple threads to do its work, and so - assuming of course that the operating system has been configured to allow the standard pthreads library to take advantage of the hardware feature, and depending on what the database has been asked to do - it should run faster on SMP machines and machines with hyperthreaded processors. As the Polyhedra software runs as an unprivileged user process, it does not need to be compiled specially for this to work.
 
For the Polyhedra-based application to work faster in such environments, there has to be some element of parallelism in the application. If one simply has a single client launching queries and transactions on the database in a serial fashion, the database itself will not go faster - but there will of course be extra CPU cycles available for any other processing that may be going on in the computer. If there a multiple clients using the Polyhedra database, then not only will the individual processes be able to be handled by separate processors, but also the separate threads in the database can be executed in parallel in separate processors.
 
(The database uses the threads for two purposes: for fault-tolerance/persistence support, and for query processing. A separate thread is used for transaction logging and for keeping the standby up to date, to avoid the database being blocked whilst this is being done. For query handling, there can either be a separate thread for each connected client, or the database can be configured to use a pool of threads that are shared between the current client connection. To allow queries to be done in parallel, an internal table-level, multiple-read, single-write locking mechanism is used. The overall effect is that a time-consuming query will not completely block queries being done on behalf of other clients; each query will see a self-consistent view of the data; and, performance is enhanced on SMP systems.)

What programming interfaces are available for the database??

Several APIs exist that can be used to interface external applications to a Polyhedra server:

  • Callback Client API - This API contains all of the active query management to interface to any Polyhedra server. This API supports active and static queries for both SQL and direct object queries. It is based on the callback model of programming (hence its name) and so is well-suited to the event-driven nature of Polyhedra.
    (NB - the libraries for this API are only provided for certain editions of Polyhedra.)

  • ODBC API - This API contains all of the active query management to interface a client application to any Polyhedra server. This API supports active and static queries for both SQL and direct object queries. It is based on the standard ODBC programming interface, but with extensions to better support the event-driven nature of Polyhedra. Polyhedra recommend the use of this API rather than the older, Callback API, as it is standards-based; also, if use is made of the SQLPrepare/SQLExecute functions, then it imposes less load on the server. On all platforms, ODBC client applications can be linked with the Polyhedra library directly, allowing them to make use of some Polyhedra-specific extensions to ODBC; alternatively, on Windows and many Linux platforms the Polyhedra library is available as an ODBC driver - in this case, the client applications would be linked with the corresponding ODBC driver manager

  • JDBC API - released in Q4 2000, this allows the Java programmer to access a Polyhedra database; the accomPanying library is written in Java, and so works with any Java engine. It uses the Polyhedra Native Protocol over TCP/IP to communicate with the Polyhedra Database Server. The release kit also contains a second set of class definitions, for use with Java engines such as CDLC that do not support JDBC.
    The driver supports JDBC 2.0 with some limitations. For 'Scrollable' result sets, all standard cursor movement methods are allowed; for 'updateable' result sets, moveToInsertRow(), updateXXX(), insertRow(), updateRow(), deleteRow(), etc., are supported. All the following settings are supported: TYPE_FORWARD_ONLY, TYPE_SCROLL_INSENSITIVE, TYPE_SCROLL_SENSITIVE.

  • ADO.NET and OLE DB - For use by Windows programmers, both an ADO.NET and an OLE DB data provider is available, which allows .NET applications and applications that understand OLE DB to access the Polyhedra database in an efficient fashion; both data provides make good use of the Polyhedra active query mechanism to notify the user code of changes in the database as they occur.
In addition, there are a number of special-purpose APIs that are collectively referred to as the Polyhedra embedded API (and documented in the 'Polyhedra on embedded systems' reference manual). These APIs can be used to 'fine-tune' the functionality of the Polyhedra database server, by providing alternative definitions of certain functions (and thus allow file-system calls to be intercepted, for example) or to provide tuning parameters to the memory management system used within the Polyhedra server.

Finally, for platforms on which Polyhedra provides an ODBC API or for which there is a Java engine that can use our JDBC driver, other options become available. For example, PHP and Python programs can interact with Polyhedra via ODBC. See here for more details.

Does Polyhedra support pessimistic locking?

Yes! With the release of Polyhedra 8.7, we now support both optimistic and pessimistic locking. We recommend the use of optimistic locks rather than pessimistic locks, as the latter are not really suited for real-time applications. 

What arbitration mechanism should I be using?

In a fault-tolerant set-up, it is important to ensure that the two Polyhedra servers know which should be master, and which should be standby - for if both think they are master, they will be operating independently (with no data synchronisation) whereas if both think they are standby, neither will be able to connect to the one they think is the current master. To allow you to control this, and determine when switch-over should occur, the Polyhedra servers use an external arbitration mechanism.

Polyhedra provides three ways for the server to communicate with the arbitration mechanism, and the choice of the one to use will depend on individual circumstances. The three ways are

  • Using an arbitration database

    This was the earliest of the three options, and is appropriate in low-volume applications, where it is not worth developing a hardware-based solution to avoid the cost of an extra computer per deployed system. In this scenario, there are two machines each running one of the Polyhedra servers that act as a fault-tolerant pair, while an independent database runs on a third machine. The third machine can be very low-specification, or it could be running other services to the overall system - a print server, say, that does not of itself need to be fault-tolerant.

    the arbitration database would have a table containing a record for each of the two FT servers, and when they start up each of the FT servers would connect to the arbitration database (using a fault-tolerant connection) and attach to 'its' record using an active query. Periodically, each FT server would update a time stamp field in its record, so that CL code running in the arbitration database (or a separate client application running on the arbitration machine, monitoring the arbitration database) can determine whether it is still live. A field in each record says whether the relevant FT server should be master or standby, and another field gives the heartbeat interval telling the server how often it should update the time stamp attribute.

    When one of the FT servers starts up, it needs to be able to connect to the arbitration database, and also - if it is to be the standby - it needs to be able to connect to the master. Apart from that, both the FT servers can survive if they temporarily lose connection to the arbitration database, provided they are in contact with their partner server. When the arbitration database restarts - or connection is re-established if it was a network failure - it allows the FT servers to tell it what mode they are currently operating in, whereas at all other times they take their orders from it. Thus, one has a resilient, software-only mechanism that survives a failure of one of the three machines or servers.

    Sample code illustrating the such a set-up is provided on request to customers and registered evaluators.

  • A simple TCP-based protocol

    In embedded applications that are going to be widely deployed, having an extra board or computer to act as an arbitrator would push the unit cost of each system too high. Instead, one would develop a hardware-based system so that one can reliably tell which of a pair of boards should be master, and which the standby. To allow your software to tell a Polyhedra server the master/standby status of the board on which it runs, a simple-TCP-based protocol has been developed. In its simplest form, you would have a process that acted as the server end of this protocol, that accepted a connection from the database process; whenever a message was received from the database server, a reply would be generated containing an indication of the board state (and thus the require master/standby state of the Polyhedra server). An example C-coded application is provided in the Polyhedra release kits. One could design a system where the arbitration processes on the two boards / machines could communicate with each other, and decide between themselves the master/standby staus. However, there are risks involved in such a setup, as it assumes an utterly reliable connection between the boards, such that a loss of a TCP/IP connection can be taken as an infallible indicator that the other server or the other board has failed.

  • A simple protocol over LINX (OSE signals)

    This is provided for the same reason as the TCP-based protocol option described above, but uses LINX (also known as OSE messages) as the transport. As a result, it is generally more appropriate to use this rather than the TCP-based option when deploying fault-tolerant Polyhedra systems under OSE, or when deploying Polyhedra alongside Enea Element (which makes heavy use of LINX).

So, to summarise, the RTRDB-based arbitration solution is only appropriate when just a few systems are likely to be deployed, or when each system will already have to have a third machine with some spare capacity. In other circumstances, the solution based on LINX will be the best if running on the OSE RTOS or alongside Element, and the simple TCP/IP-based solution is applicable in all other cases.

Does generation of a snapshot block transactions on the database?

(The following answer applies to Polyhedra32 IMDB, Polyhedra64 IMDB and Polyhedra Lite. Polyhedra Flash DBMS is different, in that it does not do journal logging (except to update a running standby server), and instead uses a technique known as shadow paging to maintain a consistent copy of the database on file.)

If one issues a ‘save’ command when using Polyhedra IMDB, the database server sets a flag on each persistent record to say that it needs to be sent to the new snapshot. Then, using a separate thread, it starts writing the new snapshot to a temporary file – first a copy of the schema and (if CL is being used) a copy of the compiled bytecode, followed by the database contents. When writing out the database contents, it does it in chunks, clearing the flag as it copies each record into a buffer.

While the dump is in process, other database transactions can occur. Queries cause no difficulties, but when it comes to updating or inserting records that still have the flag set, the database server clears the flag – but first puts a copy of the original state to one side, and it is this copy that is sent to the snapshot file when its turn comes.

When the snapshot file is complete, the original file is renamed as a backup, and the temporary file is given the name of the original file. (This avoids a ‘window of vulnerability’ where there is no valid snapshot. To guard against a system crash while the rename games are taking place, a start-up script can check for the existence of the database file before starting the database, and if not present it can rename the backup file as the database file.) The database server now writes new journal records to the end of the new snapshot, including any journal records that have been cached whilst the snapshot is in progress.

If the ‘save into <filename>’ form had been used, then the process is similar, except that the database server does not need to cache journal records: it can write them to the end of the main database file, as normal.

Thus, producing a snapshot does not block the database from servicing queries and other transactions. The only caveat is this: if a ‘save’ command is issued (not a ‘save into’), and another client issues a transaction using our ‘safe commit’ mechanism (where the acknowledgement of the successful transaction is delayed until the server has journalled away the transaction), then the acknowledgement is delayed until the journal record is written to the NEW database file.

What is the effect of journal_queue_size on the above? Well, if the database is being updated very quickly, the limit on the size the journal queue means the database server will start blocking transactions if the journal records are being produced too fast for the disk (or the standby, when one is present) to keep up. With regards to snapshots, it affects how much journal information can be cached before the database server stops blocking transactions that alter the database contents. Note that the journal queue limit is a size constraint, not a limit on the number of transactions – so it is possible that one big transaction might fill up the queue, whereas a number of smaller transactions might only partly fill it.

Turning now to standby start-up, the main database server uses a similar technique – except that it has to send over all (non-local) records, not just the persistent stuff. The master server does not consider the standby being ready until the initial snapshot has been transferred – so if a transaction with the safe-commit flag is performed after the standby has gone ready but before all the cached journal records have been transferred, acknowledgement of the new transaction will have to wait until the standby has fully caught up. As before, the maximum journal queue size might mean that the server has to block transactions – particularly if the database is large, the network is slow, and the transaction rate is high.


How do I...

There is a separate section of this site with some detailed description on how to achieve certain effects with Polyhedra. The most common 'how' question, though, is:

How can I design my application to get the best performance?

There is no hard and fast design rules for this. However, there are some general principles that can be applied:
  • Get the schema right

    • You have to know your data and how it will be used, and then design the schema accordingly.
    • Use inheritance where appropriate - this makes many queries much more efficient, avoiding the need for joins.
    • Denormalise to make the 'usual' queries easier (and use CL to maintain the integrity otherwise lost by the denormalisation)
    • Add indexes (sparingly) to speed up your normal queries.
    • Use varchar(n) rather than char when fields have a known size limit. This way, the field value is stored 'in record' instead of having a pointer to a dynamically-created buffer of the right size.

  • make use of CL in the database. This is efficient, with the following benefits:

    • it reduces the work of the clients making changes: integrity checks and 'knock-on' changes become the responsibility of the database designer, and client code is simplified;
    • integrity checks can be as complex as needed, and can be improved/extended without having to alter client applications; and,
    • it run within database, within transaction, and so cheap to perform and reduces client-server traffic.
       
  • Use active queries where appropriate. This avoids polling, less load. However, you should…

    • consider putting 'minimal intervals' on your queries; this reduces strain on server and comms when data is changing very rapidly;
    • simplify and restrict your queries - in particular, avoid joins, order by, and the use of select * (instead, specify the columns you want);
    • ensure all shared and virtual attributes are 'hidden'; and,
    • consider putting a row limit on your query.

  • Reduce client-server interaction. For example, you could...

    • batch up changes into larger transactions, where the logic of your application makes this legal and reasonable;
    • set off queries, etc in parallel - the library code will combine messages where possible;
    • use the 'update and SELECT' mechanism where appropriate. Polyhedra allows a query (other than an active query) to consist of a sequence of semicolon-sepated SQL DML statements (insert, update, delete, send) followed by a single SELECT statement. The changes are done as a single transaction, and, if successful the database then executes the select statement without any intervening transactions.
    • use Polyhedra's INSERT OR UPDATE SQL extension where appropriate. This can save an application having to check whether a record exists before updating it!
    • If using ODBC and find yourself frequently using the same SQL statement, differing only in the values supplied, consider using SQLPrepare once at the start of the program (with question-marks for the values), and SQLExecute whenever you need to invoke the statement. The values are read from locations you specify and transferred across in native format, so the message size is reduced - and the as the database server will have parsed the statement in advance, it also has less work to do.

  • Get the algorithms right!

  • An obvious point, perhaps, but one that unfortunately needs stressing. Careless coding or database design can cause an operation that should be, say, proportional to the number of records in a table to degenerate to something that is proportional to the square of the number of records, with disastrous consequences to overall performance as the table grows in size!
Users with a support contract can ask the help desk for advice on how to use particular features of the product, and Enea offers consultancy services such as design and code review to help you make best use of the system, and so help you get your Polyhedra-based product working (and to market) faster.