Improve median translations (#570)

Fixes #419
r-dbi · Nov 8, 2023 · f371c54 · f371c54
1 parent 2b3f5ef
commit f371c54
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Showing 3 changed files with 19 additions and 5 deletions.
diff --git a/NEWS.md b/NEWS.md
@@ -1,5 +1,8 @@
 # bigrquery (development version)
 
+* `median()` gets a translation that works in `summarise()` and a clear
+  error if you use it in `mutate()` (#419).
+
 * `dbGetQuery()`/`dbSendQuery()` gains support for parameterised queries via 
   the `params` argument (@byapparov, #444).
 

diff --git a/R/dplyr.R b/R/dplyr.R
@@ -252,9 +252,6 @@ sql_translation.BigQueryConnection <- function(x) {
       pmax = sql_prefix("GREATEST"),
       pmin = sql_prefix("LEAST"),
 
-      # Median
-      median = function(x) dbplyr::build_sql("APPROX_QUANTILES(", x, ", 2)[SAFE_ORDINAL(2)]"),
-
       runif = function(n = n(), min = 0, max = 1) {
         RAND <- NULL # quiet R CMD check
         dbplyr::sql_runif(RAND(), n = {{ n }}, min = min, max = max)
@@ -269,7 +266,12 @@ sql_translation.BigQueryConnection <- function(x) {
       sd =  sql_prefix("STDDEV_SAMP"),
       var = sql_prefix("VAR_SAMP"),
       cor = dbplyr::sql_aggregate_2("CORR"),
-      cov = dbplyr::sql_aggregate_2("COVAR_SAMP")
+      cov = dbplyr::sql_aggregate_2("COVAR_SAMP"),
+
+      # Median
+      median = function(x, na.rm = TRUE) {
+        dbplyr::build_sql("APPROX_QUANTILES(", x, ", 2)[SAFE_ORDINAL(2)]")
+      }
     ),
     dbplyr::sql_translator(.parent = dbplyr::base_win,
       all = dbplyr::win_absent("LOGICAL_AND"),
@@ -280,7 +282,9 @@ sql_translation.BigQueryConnection <- function(x) {
       cor = dbplyr::win_absent("CORR"),
       cov = dbplyr::win_absent("COVAR_SAMP"),
 
-      n_distinct = dbplyr::win_absent("n_distinct")
+      n_distinct = dbplyr::win_absent("n_distinct"),
+
+      median = dbplyr::win_absent("median")
     )
   )
 }

diff --git a/tests/testthat/test-dplyr.R b/tests/testthat/test-dplyr.R
@@ -137,6 +137,13 @@ test_that("runif is correctly translated", {
   )
 })
 
+test_that("median is correctly translated", {
+  expect_equal(
+    dbplyr::translate_sql(median(x), con = simulate_bigrquery(), window = FALSE),
+    dbplyr::sql("APPROX_QUANTILES(`x`, 2)[SAFE_ORDINAL(2)]")
+  )
+})
+
 test_that("can correctly print a lazy query", {
   con <- DBI::dbConnect(
     bigquery(),