[QGIS-trac] [Quantum GIS] #1866: Add a "Merge" tool to the Ftools toolbox

[Quantum GIS]

#1866: Add a "Merge" tool to the Ftools toolbox
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   Reporter:  lutra                             |              Owner:  cfarmer      
       Type:  enhancement                       |             Status:  new          
   Priority:  major: does not work as expected  |          Milestone:  Version 1.2.0
  Component:  Python plugins and bindings       |            Version:  HEAD         
   Keywords:                                    |   Platform_version:               
   Platform:  All                               |           Must_fix:  No           
Status_info:  0                                 |  
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 ''"Merge: This geoprocess can work with many input layers. It merges all
 of
 these creating a new result layer which has a feature for each feature
 of all input layers. Because each input layer could have its own
 alphanumeric schema, user must select which layer will preserve its
 schema. The rest of input layers will only preserve those attributes
 whose name and type would be the same that an attribute of the input
 layer whose schema will be preserved."''

 As described in the above definition of "merge" it is necessary to select
 a "base" layer (the one that will preserve its schema) and how many other
 layer to merge with it. If too complicated it would be enough to have the
 chance to select the "base" layer and just another one.

 This for instance would be the approach used by gvSIG. Another option but
 would be
 the Arcgis approach: when selecting the layers (two or more) to be merged,
 the interface creates a list of all columns available and leave the user
 select what columns to keep and what columns not to use.

 If there are columns with the same name, then they are not replicated (so
 the values of columns of different layers will be merged into the same
 column) and if they are of different type, than the type of the column of
 the first selected layer is used.

 This approach is more flexible but has one disvantage: in some cases, when
 there are columns with the same name but different type, the operation
 fails. Example: when it cannot copy a text value into a numeric type
 column.

 If the latter approach will be used then this detail should be considered.

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Ticket URL: <https://trac.osgeo.org/qgis/ticket/1866>
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