arcengine 查询 Recyle参数测试-优快云博客

本文探讨了Recycling参数在GIS查询中的作用，特别是在只读访问场景下。通过对比实验表明，设置Recycling为True能显著提升查询速度。

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助中有如此论述，指出recycling参数的主要性：

TheRecyclingparameter controls feature object allocation behavior. Recycling cursors rehydrate a single feature object on each fetch and can be used to optimize read-only access, for example, when drawing. It is illegal to maintain a reference on a feature object returned by a recycling cursor across multiple calls to NextFeature on the cursor. Feature objects returned by a recycling cursor should not be modified.

Non-recycling cursors return a separate feature object on each fetch. The objects returned by a non-recycling cursor may be modified and stored with polymorphic behavior. The geodatabase guarantees 'unique instance semantics' on non-recycling feature objects fetched during an edit session.

Recycling cursors should be used only for drawing and read-only access to object state. Use non-recycling search cursors to fetch objects that are to be updated.

通过下面的函数可以测试该参数的重要性：

Const N = 100000

Sub TestRecycle()
Dim amap As IMxDocument
Set amap = ThisDocument

Dim lyr As IFeatureLayer
Set lyr = amap.FocusMap.Layer(0)
Dim fc As IFeatureCursor

Dim qr As IQueryFilter
Set qr = New QueryFilter
qr.WhereClause = "objectID < " & N
Dim dt As Date

Debug.Print "Recyle: False"
dt = Now
Set fc = lyr.Search(qr, False)
While Not fc.NextFeature Is Nothing

Wend
Debug.Print "Seconds: " & DateDiff("s", dt, Now)

dt = Now
Debug.Print "Recyle: True"
Set fc = lyr.Search(qr, True)
While Not fc.NextFeature Is Nothing

Wend
Debug.Print "Seconds: " & DateDiff("s", dt, Now)

End Sub