IDifferencer Interface

  • Reference

Definition

Namespace:
Microsoft.SqlServer.Management.Sdk.Differencing
Assembly:
Microsoft.SqlServer.Management.Sdk.Sfc.dll
Package:
Microsoft.SqlServer.SqlManagementObjects v150.18208.0
Package:
Microsoft.SqlServer.SqlManagementObjects v160.2004021.0

This interface defines the Differential Service on SFC and SMO objects. The service walks and compares two specified graphs and returns an Diffgram (IEnumerable<DiffEntry>) representing the difference.

It is late-activated, meaning that it does not walk the graphs until the enumerator is accessed.

public interface IDifferencer
type IDifferencer = interface
Public Interface IDifferencer

Methods

CompareGraphs(Object, Object)

Compares two graphs (defined below) and returns the difference.

The result of CompareGraphs represents the difference to be applied to the target to obtain the source. (i.e., target + diff => source)

To support both SMO and SFC, the input are left as 'object' type. However, it allows only SqlSmoObject or SfcObject. This method throws InvalidArgumentException if the type of the specified objects is invalid.

Two graphs are said to comparable (i.e., have the same type), if they have the same structure at all levels, which means each node has the same type of children and properties. If the specified graphs are not comparable, this method throws InvalidArgumentException.

When a nodes on each graph has the same identity (represented by Urn in both SMO and SFC), it is said to be identical. When two identical nodes have the same values for all Properties, they are said to be equivalent (disregard the children they have).

During the comparison, this Service will examine all relevant nodes. (The relevance of nodes and properties is domain-specific.) For each pair of identical nodes from both sides, the Service compares all relevent Properties. If the nodes are not equivalent, a DiffEntry with DiffType.Updated are added to the result. The children will then be compared.

When a child appears in the source but not in the target, an DiffEntry with DiffType.Created is added to the result, likewise for DiffType.Deleted.

The Differencer walks the children (of all level) of a Created or Deleted node. The children entries are included in the result.

Finally, each pair of identical children is checked for equivalence.

CompareGraphs() scales to very large graphs and does not retain the entire graphs in memory if possible. Applications using this service should not have logic that depends on the ordering of the results, which may be different when the implementation changes in the future for further optimization.

The current implementation walks the tree in late-activate fashion. Resetting the result IEnumerator might result in the graphs being walked again.

The result IDiffgram is not thread-safe.
IsTypeEmitted(DiffType)

True to indicate the specified DiffType entries are included in the result diffgram.
SetTypeEmitted(DiffType)

Set the specified DiffType to be included in the result diffgram. This option affects the DiffEntry only if it is set before CompareGraphs() is called.
UnsetTypeEmitted(DiffType)

Unset (or clear) the specified DiffType to be excluded from the result diffgram. This option affects the DiffEntry only if it is set before CompareGraphs() is called.

Applies to