Streams are a key model component. They represent a structured store of data within PhixFlow receiving data from one or more components, processing it then storing it.
Stream Properties
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The tab toolbar has the following additional buttons:
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| Field | Description | |||||||||
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| Name | The name of the stream. | |||||||||
| Enabled | Whether or not the stream is enabled to run
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| Static Data | If ticked, this stream can be used
Static data is reference or "look up" data that is used as part of a stream calculation. Updating a static streamStatic streams are not updated during an analysis run that is initiated on another stream in the model. Instead, to update the data in a static stream you must run analysis directly on the stream
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| Period | This is Select the time period of for the stream. This can be either a regular period, or variable. There are four possible settings:
When the period is first set to Transactional the UID stream attribute will be created As transactional streams need a | |||||||||
| Stream Type | Select the stream type. The type of function used to generate this stream. Possible stream types are:indicates the function that operates on the data.
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| Supersede Items on Pipe | You can select Select a " loop " pipe - that is, a pipe linking pipe from the list of those available. A loop pipe links the stream back into to itself - in this field. If you do, new records will be compared to existing records, using the selected loop pipe, and if a repeated record is found, the old one will be marked as 'superseded'. It compares new data records to the existing data records. If there is a repeated record PhixFlow uses the new one in the stream and marks the old one as | |||||||||
| Audit Manual Changes | Only applies when period This check box is available when the Period is Transactional. If ticked, updates and deletes
When Audit Manual Changes is first set, the attributes
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- Right-click an attribute name to display the context menu.
- Select Edit the expression field.
- PhixFlow opens a simple text editor box
- Make changes to the attributes expression.
- Click
to save your changes.
| Field | Description |
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| Name | Name Enter the name of the Attributeattribute. |
| Type | This can be one of:Select the attribute type for the data. |
| Length/ Precision/Significant Figures | For a This option is available when Type is String, Integer or Decimal. Specify
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| Scale | Only applies to Decimal types. The number of digits after the decimal point; must be less than the number of significant figures. |
| Local | Only tick this box if this attribute is only required as part of the stream calculation, and it is not necessary to keep the result. |
| Order | The order of the attributes in the stream. This is important because the stream attribute expressions are evaluated in this order. If the results of an attribute expression, or a $ variable calculated during its calculation, are required in the expression of a second attribute - the second attribute must come after the first in the attribute list. |
| Expression | The expression used to generate the attribute value. This is written as a PhixFlow Expression. It must evaluate to a single value, of the type specified in the Type field. |
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| Field | Description | ||
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| Indexed | Tick this option if this field should be indexed in the underlying database. An indexed field should be used to increase performance on very large streams in the following situations:-
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| Filter conditions are case-independent by default | If ticked, new filter conditions on this field are case-insensitive by default. The filter window → Ignore Case check box inherits this setting; see Filters on Data Views. For case-insensitive filters, there is no difference if the attribute is also indexed.
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| Key | For in-memory streams, whether this field will be used as a key value. See How To: Summarise unsorted data with In Memory Streams. | ||
| Cache Key | If a cache key is set, the value of this attribute persists throughout the stream calculation, rather than being created from scratch for each stream item as normal. This allows you to keep track of the calculation as it progresses. The cache key is an expression that is evaluated for each stream item, and of course it can use the existing value of the attribute, in other words, to value it had in the previous stream item processed in the stream calculation. This allows expressions to use the "persistent" attribute value on subsequent stream items. The expression provided in the Cache Key is evaluated for each stream item so that this "persistent" attribute can refer to multiple value keyed on the "Cache Key". |
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In the cases where a mixture of the full archive fields Keep for X Days, Keep for Y StreamSets' and the superseded archive fields Keep Superseded for X Days, Keep Superseded for Y StreamSets are populated, then the full archive values will be first applied and the resultant stream item records will be archived and deleted. Only then will the remaining stream sets use the Keep Superseded ... values to apply a further condition to archive and delete any remaining non qualifying superseded records.
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If you load data without specifying a type what happens?
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Which fields can have "null"?
String
Apply a string type to sequences of characters (i.e., letters, numerals, symbols and punctuation marks). By default string attribute types have a fixed length of how long?
do we need to tell users about any information-loss if data that is naturally a different type gets loaded as a string?
Anchor Bigstring Bigstring
Bigstring
| Bigstring | |
| Bigstring |
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The maximum bigstring size can be configured in System Configuration → System Tuning → Maximum Bigstring Size.
Integer
Apply an integer type to whole numbers (not a fractions or decimals) that can be positive, negative, or zero.
What happens if you attempt to load a float or decimal number into an integer attribute?
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