[Firebird-checkins] SF.net SVN: firebird:[59898] firebird/trunk

[<asf...@us...>]

Revision: 59898
          http://sourceforge.net/p/firebird/code/59898
Author:   asfernandes
Date:     2014-07-21 02:37:58 +0000 (Mon, 21 Jul 2014)
Log Message:
-----------
Fixed CORE-4488 - Wrong results of FOR SELECT <L> FROM <T> AS CURSOR <C> and table <T> is modified inside cursor's begin...end block.

Modified Paths:
--------------
    firebird/trunk/doc/sql.extensions/README.cursor_variables.txt
    firebird/trunk/src/dsql/ExprNodes.cpp

Modified: firebird/trunk/doc/sql.extensions/README.cursor_variables.txt
===================================================================
--- firebird/trunk/doc/sql.extensions/README.cursor_variables.txt	2014-07-21 00:32:30 UTC (rev 59897)
+++ firebird/trunk/doc/sql.extensions/README.cursor_variables.txt	2014-07-21 02:37:58 UTC (rev 59898)
@@ -21,7 +21,10 @@
     4) Cursor variables are read-only.
     5) A FOR SELECT without AS CURSOR needs the use of INTO, while with AS CURSOR it's not required,
        but still allowed. With FETCH, INTO is now optional.
-	6) It's allowed now to use the colon prefix when assigning to variables or NEW's fields.
+    6) It's allowed now to use the colon prefix when assigning to variables or NEW's fields.
+    7) Reading from a cursor variable returns the current field values. That means an UPDATE (with
+       WHERE CURRENT OF) also updates the fields for subsequent reads. And DELETE (with WHERE
+       CURRENT OF) makes subsequent reads to return NULL.
 
   Examples:
     1.

Modified: firebird/trunk/src/dsql/ExprNodes.cpp
===================================================================
--- firebird/trunk/src/dsql/ExprNodes.cpp	2014-07-21 00:32:30 UTC (rev 59897)
+++ firebird/trunk/src/dsql/ExprNodes.cpp	2014-07-21 02:37:58 UTC (rev 59898)
@@ -6820,6 +6820,16 @@
 				dsqlScratch->appendUChar(derivedContexts[i]);
 		}
 	}
+	else if ((context->ctx_flags & CTX_cursor) && val->is<FieldNode>())
+	{
+		// ASF: FieldNode::execute do not verify rpb_number.isValid(), and due to system triggers
+		// and also singular queries, we cannot start to do it. So to fix CORE-4488, we introduce
+		// the usage of blr_derived_expr for cursor fields, which in practice prefixes the
+		// FieldNode::execute by a test of rpb_number.isValid().
+		dsqlScratch->appendUChar(blr_derived_expr);
+		dsqlScratch->appendUChar(1);
+		GEN_stuff_context(dsqlScratch, val->as<FieldNode>()->dsqlContext);
+	}
 
 	GEN_expr(dsqlScratch, value);
 }

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