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Fiona Sargeant (Unlicensed)

Fiona Sargeant (Unlicensed)

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Overview

Use the stream attributes properties tab to specify the characteristics of the the data in a table column.  

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Stream Attribute Properties

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Basic Settings

FieldDescription
NameEnter the name of the attribute.
TypeSelect the attribute type for the data.
  • String for text strings 
  • Bigstring for text
  • Integer for text
  • Float for text
  • Decimal for text
  • Date for text
  • Datetime for text
  • Graphic for text
  • TrueFalse for text

Length

This field is available when Type is String. Enter the maximum number of characters allowed in text data. For unlimited text strings, set a Type of  Bigstring. 

PrecisionThis field is available when Type is Integer. Enter the maximum number of digits allowed in whole numbers.
Significant FiguresThis field is available when Type is Decimal. Enter the maximum number of total digits for decimal numbers. 

For example, to specify numbers must have two digits before and after the decimal point, such as 12.34, enter:

Significant Figures  4

Decimal Places  2

Decimal Places

This field is available when Type is Decimal. Enter the maximum number of digits allowed after the decimal point.

This must be less than the number of significant figures.


Local

In most cases leave this option 

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 to keep both stream data and any result of using it in a calculation.

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 for an attribute that you need to use in a stream calculation, but you do not need to keep the result.

Order

The order of the attributes in the stream. Stream attribute expressions are evaluated in this order. 

This is important when you need to use the results of a calculation in another attribute:

  • either in its expression
  • or in a $ variable 

In the attribute list, the attribute that calculates the result must come before the attribute that requires the result.

ExpressionThe 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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FieldDescription
Indexed

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 to index this attribute in the underlying database.

To improve performance, index an attribute when the stream has a large data set and an output pipe from the stream uses this attribute to:

  • filter the stream data
  • sort or group the stream data.
Filter conditions are
case-independent by default

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 to set new filter conditions on this attribute to be 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. 

Note
This option affects the behaviour of filters for PhixFlow instances running on Oracle or MariaDB (MySQL) databases.
For PhixFlow instances running on a SQL Server database, filters are always case-independent.


Key

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 for in-memory streams, to specify that this field will be used as a key value. 

Cache Key

Enter an expression to be evaluated for each stream item (data record) in the stream. The expression can

  • either use the value of this attribute
  •  or calculate a different value

Once calculated, the cache key value persists throughout subsequent 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.

This means you can use a "persistent" attribute value in other expressions. 

CHECK THIS

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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

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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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