Correclty compute row count when fetching more rows than exist

Fixes #501

NEWS.md

@@ -1,5 +1,8 @@
 # bigrquery (development version)
 
+* `dbGetRowCount()` and `dbHasComplete()` now return correct values when you
+  try to fetch more rows than actually exist (#501).
+
 * `dbReadTable()`, `dbWriteTable()`, `dbExistsTable()`, `dbRemoveTable()`,
   and `dbListFields()` now all work with `DBI::Id()` (#537).
 

R/dbi-result.R

@@ -119,7 +119,7 @@ setMethod(
       bigint = res@bigint,
       quiet = res@quiet
     )
-    res@cursor$adv(n)
+    res@cursor$adv(nrow(data))
 
     data
   })

tests/testthat/test-dbi-result.R

@@ -43,6 +43,20 @@ test_that("can retrieve query in pieces and that quiet is respected", {
   expect_true(DBI::dbHasCompleted(res))
 })
 
+test_that("dbHasCompleted() is accurate if you fetch past end", {
+  con <- DBI::dbConnect(
+    bigquery(),
+    project = bq_test_project(),
+    dataset = "basedata"
+  )
+
+  res <- DBI::dbSendQuery(con, "SELECT cyl FROM mtcars LIMIT 5")
+  df <- DBI::dbFetch(res, 10)
+
+  expect_equal(DBI::dbGetRowCount(res), 5)
+  expect_true(DBI::dbHasCompleted(res))
+})
+
 test_that("can get metadata", {
   con <- DBI::dbConnect(
     bigquery(),