Set the LOB prefetch length attribute in order to reduce the number o…

…f round

trips to determine the length and chunk size of the LOB.

src/dpiImpl.h

@@ -264,6 +264,7 @@ extern unsigned long dpiDebugLevel;
 #define DPI_OCI_ATTR_CONNECTION_CLASS               425
 #define DPI_OCI_ATTR_PURITY                         426
 #define DPI_OCI_ATTR_RECEIVE_TIMEOUT                436
+#define DPI_OCI_ATTR_LOBPREFETCH_LENGTH             440
 #define DPI_OCI_ATTR_SUBSCR_IPADDR                  452
 #define DPI_OCI_ATTR_UB8_ROW_COUNT                  457
 #define DPI_OCI_ATTR_SPOOL_AUTH                     460

src/dpiStmt.c

@@ -479,6 +479,7 @@ static int dpiStmt__define(dpiStmt *stmt, uint32_t pos, dpiVar *var,
 {
     void *defineHandle = NULL;
     dpiQueryInfo *queryInfo;
+    int tempBool;
 
     // no need to perform define if variable is unchanged
     if (stmt->queryVars[pos - 1] == var)
@@ -513,6 +514,15 @@ static int dpiStmt__define(dpiStmt *stmt, uint32_t pos, dpiVar *var,
             return DPI_FAILURE;
     }
 
+    // specify that the LOB length should be prefetched
+    if (var->nativeTypeNum == DPI_NATIVE_TYPE_LOB) {
+        tempBool = 1;
+        if (dpiOci__attrSet(defineHandle, DPI_OCI_HTYPE_DEFINE,
+                (void*) &tempBool, 0, DPI_OCI_ATTR_LOBPREFETCH_LENGTH,
+                "set lob prefetch length", error) < 0)
+            return DPI_FAILURE;
+    }
+
     // define objects, if applicable
     if (var->buffer.objectIndicator && dpiOci__defineObject(var, defineHandle,
             error) < 0)