From b10fcbcb273704026641a07e3d09643798a431dd Mon Sep 17 00:00:00 2001
From: Boris Kolpackov <boris@codesynthesis.com>
Date: Wed, 19 Nov 2014 13:54:38 +0200
Subject: Allow empty runtime and execute views

Use them to handle INSERT/UPDATE SQL Server stored procedures.
---
 odb/mssql/statement.cxx       | 38 ++++++++++++++++++++++++--------------
 odb/mssql/statement.hxx       |  1 +
 odb/mssql/view-statements.hxx |  4 +++-
 3 files changed, 28 insertions(+), 15 deletions(-)

diff --git a/odb/mssql/statement.cxx b/odb/mssql/statement.cxx
index 00180ee..e87374b 100644
--- a/odb/mssql/statement.cxx
+++ b/odb/mssql/statement.cxx
@@ -862,16 +862,19 @@ namespace odb
       // Skip result sets that have no columns. These seem to be added
       // by DML statements that don't produce any result (e.g., EXEC).
       //
-      SQLSMALLINT cols (0);
-
-      while (cols == 0)
+      for (columns_ = 0; columns_ == 0;)
       {
-        r = SQLNumResultCols (stmt_, &cols);
+        {
+          SQLSMALLINT c;
+          r = SQLNumResultCols (stmt_, &c);
 
-        if (!SQL_SUCCEEDED (r))
-          translate_error (r, conn_, stmt_);
+          if (!SQL_SUCCEEDED (r))
+            translate_error (r, conn_, stmt_);
+
+          columns_ = static_cast<SQLUSMALLINT> (c);
+        }
 
-        if (cols == 0)
+        if (columns_ == 0)
         {
           r = SQLMoreResults (stmt_);
 
@@ -887,7 +890,7 @@ namespace odb
       // of this assertion is a native view with a number of data members
       // not matching the number of columns in the SELECT-list.
       //
-      assert (static_cast<SQLUSMALLINT> (cols) == result_count_ + long_count_);
+      assert (columns_ == result_count_ + long_count_);
     }
 
     select_statement::result select_statement::
@@ -898,15 +901,22 @@ namespace odb
       if (cc != 0 && cc->callback != 0)
         (cc->callback) (cc->context);
 
-      SQLRETURN r (SQLFetch (stmt_));
-
-      if (r == SQL_NO_DATA)
+      // Don't bother calling SQLFetch() if there are no columns.
+      //
+      if (columns_ == 0)
         return no_data;
+      else
+      {
+        SQLRETURN r (SQLFetch (stmt_));
 
-      if (!SQL_SUCCEEDED (r))
-        translate_error (r, conn_, stmt_);
+        if (r == SQL_NO_DATA)
+          return no_data;
 
-      return success;
+        if (!SQL_SUCCEEDED (r))
+          translate_error (r, conn_, stmt_);
+
+        return success;
+      }
     }
 
     void select_statement::
diff --git a/odb/mssql/statement.hxx b/odb/mssql/statement.hxx
index 1c012ce..36c87f1 100644
--- a/odb/mssql/statement.hxx
+++ b/odb/mssql/statement.hxx
@@ -201,6 +201,7 @@ namespace odb
       binding& result_;
       SQLUSMALLINT result_count_; // Actual number of columns bound.
       SQLUSMALLINT long_count_;   // Number of long data columns.
+      SQLUSMALLINT columns_;      // Number of columns in result set.
     };
 
     struct LIBODB_MSSQL_EXPORT auto_result
diff --git a/odb/mssql/view-statements.hxx b/odb/mssql/view-statements.hxx
index beb8d62..7a315a9 100644
--- a/odb/mssql/view-statements.hxx
+++ b/odb/mssql/view-statements.hxx
@@ -70,7 +70,9 @@ namespace odb
       image_type image_;
       std::size_t image_version_;
       binding image_binding_;
-      bind image_bind_[view_traits::column_count];
+      bind image_bind_[view_traits::column_count != 0
+                       ? view_traits::column_count
+                       : 1];
     };
   }
 }
-- 
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