Caches
The Cache data source was specifically
designed to enable high-speed analytic processing of real-time data and the
comparison of current real-time values against history data, either visually or
as input to alert rules that activate automated behavior.
The Cache data source allows for easy
definition of a memory resident data cache that can store current scalar values,
tabular data with optional filters, as well as time-stamped scalar or tabular
data (up to a configurable number of entries), which keeps only the most current
information and discards older entries. A cache
history can be configured to time-stamp incoming data or to recognize a
time-stamp already included in incoming data. You can also optionally pre-load a
cache with data from another source, for example if you have historical
information stored in a database.
In many real-time situations, data enters
the system asynchronously. For example, in a financial trading application a
series of data might be delivered that contains multi-dimensional data about a
particular trading instrument. You might want to store the current value of a
particular market data feed based on the instrument name index (IBM) and the
activity index ("buy") and require a time-stamped history of this market data to
analyze the trend of a particular instrument over a period of time.
The Cache data source allows for much higher
performance than the traditional means of either performing analytics on
information stored in a database or querying it back out of the database when it
is necessary to make calculations.
Adding
Caches
In the Display Builder, select Tools>Caches
to open the Caches dialog. When you have finished adding all of your
caches and configuring their properties, Save the
display (.rtv) file and add this Cache
Definition file to the
Cache data source
configuration.
| |
|
| Add |
To add a new cache,
click Add and enter a cache name and select a cache type. Once you have
added a cache, select that cache from the list and edit properties in the Object
Properties dialog. |
| Cache
Name |
Enter a
unique name for each cache listed. Caches that do not specify a name, as well as caches with
a duplicate names, will not be created and an error will print to the
console. |
| Cache
Type |
Choose a type of cache
from the drop down menu (Table
or Double). |
| Copy |
Select a cache from
the list and click Copy to create a duplicate of that cache. NOTE: You must
enter a unique name for each copy
you make.
To copy a cache from your current display to
another display (.rtv) file, select a cache from the list and
click the Copy button 
in the toolbar (or Ctrl-C). Then open the other display (.rtv) file and
click the Paste button 
(or Ctrl-V). If a cache by that name already exists in that display
(.rtv) file, you will need to rename the cache.
NOTE: A cache pasted into another
display (.rtv) file will have the same data attachments as the original cache. |
| Remove |
Select a
cache from the list and click Remove to delete. |
| Display
Content |
Select a cache from the
list that is attached to data and click Display Content to view the
contents of the attached current and/or history table(s). |
| List All
Caches |
Select to view caches
from all display (.rtv) files and included
files. NOTE: Only properties for caches defined within the
current display (.rtv) file can be modified. |
Cache Definition Files
To create an Cache Definition file, save
the display (.rtv) file that contains the cache definition properties you set. See Application Options for
details on how to add a Cache Definition file to the Cache data source
configuration.
Viewing Caches
See the Attach to Cache Data section
for more information on attaching to cache data variables.
Table Cache
The Table Cache allows you to cache your
tabular data. Attach your input data to the valueTable property.
Cache Properties
|
allowDuplicatesInHistoryFlag |
If this property is
deselected, then before adding a new row to the History table the cache data
source will first check if an existing row has the identical timestamp and index
column values. If a duplicate does exist, the existing row will be replaced with
the new row.
NOTE: If duplicate history rows are acceptable or
unlikely to occur, then it is recommended that this property remain selected to maintain optimum
performance. |
| cacheName |
A unique name for the
cache. An
entry for this property is required.
Caches that do not specify a cacheName,
as well as caches with duplicate cacheName properties, will not be
created and an error will print to the console. |
|
indexColumnNames |
Enter a semicolon (;) separated
list of column names from the attached valueTable to be used as index columns.
|
|
indexColumnNamesForDelete |
Enter a semicolon (;)
separated list of column names from the attached valueTable from which
defunct rows will be removed. That is, any rows in the current cache table that
contain values in the specified indexColumnNamesForDelete that were not
updated. These static rows are considered defunct and removed from the current
cache table. |
|
timeSpan |
Amount of time that
rows will be kept in the History table according to their timestamp. Specify the
duration in seconds or specify a number followed by a single character
indicating the desired time interval (e.g. 15m for 15 minutes). Valid
characters are as follows:
| y |
years (365 days) |
| M |
months (31 days) |
| w |
weeks (7 days) |
| d |
days |
| h |
hours |
| m |
minutes |
| s |
seconds |
The timeSpan property only determines the
duration of rows kept in the History table by the cache data source. It does not
affect database storage, if any, associated with the cache.
NOTE: The maxNumberOfRows property will
limit the total number of rows in the History table regardless of the specified
timeSpan. |
|
timestampColumnName |
Specify the name of a
timestamp column. If the specified timestampColumnName is not found in
the incoming data, a column will be inserted and each row will contain the time
that row was received. |
Data Properties
|
deleteTable |
For an indexed table
cache, this is a data attachment which will cause selected rows to be removed
from the cache tables. Rows will be removed if their index column values match
those of a row in the table data coming from this attachment. |
|
initialTable |
Attach this property to
a table containing initial values for the cache. This table must contain the
same column(s) as the input table attached to valueTable, as well as a
timestamp column if timestampColumnName is specified. NOTE:
If the specified timestampColumnName is not found in
the incoming data, a column will be inserted. Data attached to this property works best if it is
only updated once at the startup of Enterprise RTView.
NOTE: A table attached the initialTable
property will be modified if you did not include a column with the
timestampColumnName and/or if the deleteTable property is updated. If
other objects in your Enterprise RTView application are attached to this same
table, those objects may also be affected. |
|
maxNumberOfRows |
Number of rows in the
History table. Default is 100. If set to 0, no History table is created and only
the Current table will be available in the Table drop down menu in the
Attach to Cache Data dialog. |
|
resetTrigger |
When data values
attached to this property receive an update the cache will be cleared.
|
|
schemaTable
|
Optionally attach this
property to any tabular data source (e.g. SQL query, XML file, etc.) to provide
the structure of a table you would like the Table Cache object to use. Only the
table's structure will be used from this data attachment, any row data will be
ignored. Once a schemaTable is
specified, Current and History tables will be initialized accordingly and the
Attach to Cache Data dialog will show the columns found in that table structure.
Once data becomes available, Table Cache objects will contain the columns found
in the specified schemaTable, in addition to columns found in the data.
NOTE: If the
data types of columns defined in the schemaTable differ from data types
found in the actual data attachment, then the schema types will be used and
incoming data will be converted.
If the specified timestampColumnName is not found in
the incoming data, a column will be inserted. |
| valueTable
|
Attach your input data
to this property if it is tabular. For scalar input data,
select the Double Cache object and attach your input data to the
value property. |
Historian Properties
You must specify your Cache definition (.rtv) file as an
Historian data configuration (,rtv) file
in order use the following object properties.
| Property
Name |
Description |
|
compactionType |
Select from the
following options:
- None - No compaction.
- Aggregate - Compact via
data aggregation.
- Displace - Compact via table
displacement.
You must specify at least one index column
via the indexColumnNames property and, where possible,
quoteColumnNamesFlag should be selected to preserve column name case.
NOTE: Based on your specified compactionRules,
use the -smoothcompaction command line
option to perform compaction on old data which currently exists in your
database from prior executions of the Historian.
|
compactionGroupBy |
This property applies
only if the selected
compactionType is Aggregate. Click on the button to specify the methods used to perform
compaction (i.e. sum, count, average, min or max). |
|
compactionRules |
Specify compaction
rules. NOTE: If the selected compactionType is Displace, then
currently this property only supports the use of one displacement rule. |
NOTE: These object properties apply to
Advanced Historian users only. |
| currentTableName |
Enter the name of a
table in your Historian database in which to store the cache's current data
table. If you specify a currentTableName and no table by that name exists
in your database, then one will be created for you the first time you run the
Historian. On each update of the data
attached to the valueTable property, the Historian will create or update
corresponding rows in the specified currentTableName in the Historian
database. The indexColumnNames property will be used to locate rows to
update otherwise, if no indexColumnNames are defined, the Historian will
replace the entire table on each update.
If the deleteTable property is used to
delete rows from the cache's current table, then Historian will also delete
those rows from the specified currentTableName table in the Historian
database.
On startup of an Enterprise RTView application,
the specified currentTableName will be queried from the Historian
database for initial rows to be loaded into the cache's current table. To
prevent this initial data from being loaded, you can run the Display Builder or
Display Viewer from a command window and use the -nohistory command line
option.
NOTE: The currentTableName property is not
supported in combination with the Historian's -kdbformat command line
option. |
| databaseName |
Name of your Historian
database that contains history and/or current tables for this cache. If left
blank, the database name RTVHISTORY is assumed. |
| historyTableName |
Enter the name of a
table in your Historian database in which to store the cache's history data
table. If you specify a historyTableName and no table by that name exists
in your database, then one will be created for you the first time you run the
Historian. When rows are appended to the
cache's history table, the Historian will also append those rows to the
specified historyTableName in the Historian database.
If you specify a timestampColumnName, the
Historian assumes that column will be used for sorting and purging rows in
chronological order and will not append its own timestamp columns to the
specified historyTableName table.
Before data is stored in the database, the
cache's schemaTable, if any, is applied.
If you specify a historyTableName,
Enterprise RTView applications will automatically query the Historian database
table for the initial rows to be loaded into the cache's history table, provided
that:
- The initialTable property is not
attached to data (indicating an explicit query has been configured to load
cache history data), and
- A timestampColumnName is specified (so
that it can be used to sort the SQL query result by time).
The number of rows loaded by this initial
query is limited by the maxNumberOfRows property. To prevent this
initial data from being loaded, you can run the Display Builder or Display
Viewer from a command window and use the -nohistory command line
option. |
| quoteColumnNamesFlag |
If selected, column
names will be quoted in all SQL queries and commands for this cache. |
Object Properties
| Property
Name |
Description |
| objName |
Name given to facilitate object management via
the Object List dialog. Select Tools>Object List. |
| objX |
Plot x-axis position of object. |
| objY |
Plot y-axis position of object. |
Double Cache
The Double Cache allows you to cache your
scalar (double) data. Attach your input data to the value
property. Cache Properties
| cacheName |
A unique name for the
cache. An
entry for this property is required.
Caches that do not specify a cacheName,
as well as caches with duplicate cacheName properties, will not be
created and an error will print to the console. |
|
timeSpan |
Amount of time that
rows will be kept in the History table according to their timestamp. Specify the
duration in seconds or specify a number followed by a single character
indicating the desired time interval (e.g. 15m for 15 minutes). Valid
characters are as follows:
| y |
years (365 days) |
| M |
months (31 days) |
| w |
weeks (7 days) |
| d |
days |
| h |
hours |
| m |
minutes |
| s |
seconds |
The timeSpan property only determines the
duration of rows kept in the History table by the cache data source. It does not
affect database storage, if any, associated with the cache.
NOTE: The maxNumberOfRows property will
limit the total number of rows in the History table regardless of the specified
timeSpan. |
|
timestampColumnName |
Specify the name of a
timestamp column. If the specified timestampColumnName is not found in
the incoming data, a column will be inserted and each row will contain the time
that row was received |
Data Properties
|
initialTable |
Attach this property to
a table containing initial values for the cache. This attachment must result in
a table with a single column of type double, as well as a timestamp column if
timestampColumnName is specified. NOTE: If the specified
timestampColumnName is not found in the incoming data, a column will be
inserted. Data attached to this property works best if it is
only updated once at the startup of Enterprise RTView.
NOTE: A table attached the initialTable
property will be modified if you did not include a column with the
timestampColumnName and/or if the deleteTable property is updated. If
other objects in your Enterprise RTView application are attached to this same
table, those objects may also be affected. |
|
maxNumberOfRows |
Number of rows in the
History table. Default is 100. If set to 0, no History table is created and only
the Current table will be available in the Table drop down menu in the
Attach to Cache Data dialog. |
|
resetTrigger |
When data values
attached to this property receive an update the cache will be cleared.
|
| value |
Attach your input data to this
property if it is scalar. For tabular input data, select the Table Cache object and attach your input data to the valueTable
property. |
Historian Properties
| Property
Name |
Description |
| databaseName |
Name of your Historian
database that contains history and/or current tables for this cache. If left
blank, the database name RTVHISTORY is assumed. |
| historyTableName |
Enter the name of a
table in your Historian database in which to store the cache's history data
table. If you specify a historyTableName and no table by that name exists
in your database, then one will be created for you the first time you run the
Historian. When rows are appended to the
cache's history table, the Historian will also append those rows to the
specified historyTableName in the Historian database.
If you specify a timestampColumnName, the
Historian assumes that column will be used for sorting and purging rows in
chronological order and will not append its own timestamp columns to the
specified historyTableName table.
Before data is stored in the database, the
cache's schemaTable, if any, is applied.
If you specify a historyTableName,
Enterprise RTView applications will automatically query the Historian database
table for the initial rows to be loaded into the cache's history table, provided
that:
- The initialTable property is not
attached to data (indicating an explicit query has been configured to load
cache history data), and
- A timestampColumnName is specified (so
that it can be used to sort the SQL query result by time).
The number of rows loaded by this initial
query is limited by the maxNumberOfRows property. To prevent this
initial data from being loaded, you can run the Display Builder or Display
Viewer from a command window and use the -nohistory command line
option. |
| quoteColumnNamesFlag |
If selected, column
names will be quoted in all SQL queries and commands for this cache. |
Object Properties
| Property
Name |
Description |
| objName |
Name given to facilitate object management via
the Object List dialog. Select Tools>Object List. |
| objX |
Plot x-axis position of object. |
| objY |
Plot y-axis position of object. |
|
