Processing: precision loss on decimal number

[qgib]

Author Name: Tobias Wendorff (Tobias Wendorff)
Original Redmine Issue: 21316
Affected QGIS version: 3.5(master)
Redmine category:processing/core
Assignee: Nyall Dawson

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Bug report

1. create a new Temporary Scratch Layer
2. add some fields
   @name: one
   type: decimal number (real)
   provider type: double

• length: 32
• precision: 30@

@name: two
type: decimal number (numeric)
provider type: numeric

• length: 20
• precision: 18@

@name: three
type: decimal number (decimal)
provider type: decimal

• length: 20
• precision: 18@

@name: four
type: decimal number (real)
provider type: real

• length: internally set to -1
• precision: internally set to -1@

@name: five
type: decimal number (double)
provider type: double precision

• length: internally set to -1
• precision: internally set to -1@

3. add a new feature
4. add the value "0.01234567890123456789" into each field (length 22, precision 20)
5. save & check results
   @- one : 0.012345678901234568430878013601

• two : 0.012345678901234567
• three: 0.012345678901234567
• four : 0.012345678901234568
• five : 0.012345678901234568@

6. When running "Refactor Fields", "Extract by Attribute" or others in Processing, the result is:
   @- one : 0.012345678901234568430878013601

• two : 0.012345678901234568
• three: 0.012345678901234568
• four : 0.01235 ["source field" shows, precision gets smashed to 5]
• five : 0.01235 ["source field" shows, precision gets smashed to 5]@

1. Expected results

The output field should have the same precision as the input field.

[qgib]

Author Name: Nyall Dawson (@nyalldawson)

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• assigned_to_id was configured as Nyall Dawson
• status_id was changed from Open to In Progress

[qgib]

Author Name: Nyall Dawson (@nyalldawson)

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Applied in changeset f3cb348.

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• done_ratio was changed from 0 to 100
• status_id was changed from In Progress to Closed