Changes between Version 1 and Version 2 of rfc54_dataset_transactions

Timestamp:

Feb 24, 2015, 1:33:15 AM (9 years ago)

Author:

Even Rouault

Comment:

drv_pg_advanced.html: explain the effect of SetAttributeFilter() or SetSpatialFilter()

rfc54_dataset_transactions

@@ -378 +378 @@
 reading from the beginning.
 
+As calling SetAttributeFilter() or SetSpatialFilter() implies an implicit
+ResetReading(), they have the same effect as ResetReading(). That is to say,
+while an implict transaction is in progress, the transaction will be committed
+(if no other layer is being read), and a new one will be started again at the next
+GetNextFeature() call. On the contrary, if they are called within an explicit
+transaction, the transaction is maintained.
+
 With the above rules, the below examples show the SQL instructions that are
 run when using the OGR API in different scenarios.
@@ -386 +393 @@
                                    FETCH 1 IN cur1
 
+lyr1->SetAttributeFilter('xxx')
+     --> lyr1->ResetReading()      CLOSE cur1
+                                   COMMIT (implicit)
+
+lyr1->GetNextFeature()             BEGIN (implict)
+                                   DECLARE cur1 CURSOR  FOR SELECT * FROM lyr1 WHERE xxx
+                                   FETCH 1 IN cur1
+
 lyr2->GetNextFeature()             DECLARE cur2 CURSOR  FOR SELECT * FROM lyr2
                                    FETCH 1 IN cur2
@@ -395 +410 @@
 lyr1->CreateFeature(f)             INSERT INTO cur1 ...
 
+lyr1->SetAttributeFilter('xxx')
+     --> lyr1->ResetReading()      CLOSE cur1
+                                   COMMIT (implicit)
+
+lyr1->GetNextFeature()             DECLARE cur1 CURSOR  FOR SELECT * FROM lyr1 WHERE xxx
+                                   FETCH 1 IN cur1
+
 lyr1->ResetReading()               CLOSE cur1
 
@@ -400 +422 @@
                                    COMMIT (implicit)
 
-
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 ds->StartTransaction()             BEGIN
@@ -412 +434 @@
 lyr1->CreateFeature(f)             INSERT INTO cur1 ...
 
+lyr1->SetAttributeFilter('xxx')
+     --> lyr1->ResetReading()      CLOSE cur1
+                                   COMMIT (implicit)
+
+lyr1->GetNextFeature()             DECLARE cur1 CURSOR  FOR SELECT * FROM lyr1 WHERE xxx
+                                   FETCH 1 IN cur1
+
 lyr1->ResetReading()               CLOSE cur1
 
@@ -418 +447 @@
 ds->CommitTransaction()            COMMIT
 
-
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 ds->StartTransaction()             BEGIN
@@ -432 +461 @@
 lyr1->GetNextFeature()             FETCH 1 IN cur1      ==> Error since the cursor was closed with the commit. Explicit ResetReading() required before
 
-
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 lyr1->GetNextFeature()             BEGIN (implicit)