adding ability to work with sqlite compiled with -DSQLITE_OMIT_DECLTYPE

fix #751

src/column.rs

@@ -86,6 +86,7 @@ impl Statement<'_> {
     }
 
     /// Returns a slice describing the columns of the result of the query.
+    #[cfg(feature = "column_decltype")]
     pub fn columns(&self) -> Vec<Column> {
         let n = self.column_count();
         let mut cols = Vec::with_capacity(n as usize);
@@ -123,6 +124,7 @@ impl<'stmt> Rows<'stmt> {
     }
 
     /// Returns a slice describing the columns of the Rows.
+    #[cfg(feature = "column_decltype")]
     pub fn columns(&self) -> Option<Vec<Column>> {
         self.stmt.map(Statement::columns)
     }
@@ -150,6 +152,7 @@ impl<'stmt> Row<'stmt> {
     }
 
     /// Returns a slice describing the columns of the Row.
+    #[cfg(feature = "column_decltype")]
     pub fn columns(&self) -> Vec<Column> {
         self.stmt.columns()
     }
@@ -157,11 +160,13 @@ impl<'stmt> Row<'stmt> {
 
 #[cfg(test)]
 mod test {
-    use super::Column;
     use crate::Connection;
 
     #[test]
+    #[cfg(feature = "column_decltype")]
     fn test_columns() {
+        use super::Column;
+
         let db = Connection::open_in_memory().unwrap();
         let query = db.prepare("SELECT * FROM sqlite_master").unwrap();
         let columns = query.columns();

src/raw_statement.rs

@@ -63,6 +63,7 @@ impl RawStatement {
         unsafe { ffi::sqlite3_column_type(self.ptr, idx as c_int) }
     }
 
+    #[cfg(feature = "column_decltype")]
     pub fn column_decltype(&self, idx: usize) -> Option<&CStr> {
         unsafe {
             let decltype = ffi::sqlite3_column_decltype(self.ptr, idx as c_int);