"ORDER BY is ignored in subqueries without LIMIT" without a subquery

With dplyr 1.0.3 and dbplyr 2.0.0, I create a query:

library(dplyr)
#> 
#> Attaching package: 'dplyr'
#> The following objects are masked from 'package:stats':
#> 
#>     filter, lag
#> The following objects are masked from 'package:base':
#> 
#>     intersect, setdiff, setequal, union
dbpool <- pool::dbPool(RPostgres::Postgres(), ...)
query <- dplyr::tbl(dbpool, dbplyr::ident_q('echo_dfr.x_cwa_limits')) %>%
dplyr::select(external_permit_nmbr) %>%
dplyr::distinct() %>%
dplyr::arrange(external_permit_nmbr)

This works fine, and gives the SQL I expect:

dplyr::show_query(query)
#> <SQL>
#> SELECT DISTINCT "external_permit_nmbr"
#> FROM echo_dfr.x_cwa_limits
#> ORDER BY "external_permit_nmbr"

So far, so good. But when I run the query, I get a warning about a subquery:

result <- dplyr::pull(query)
#> Warning: ORDER BY is ignored in subqueries without LIMIT
#> i Do you need to move arrange() later in the pipeline or use window_order() instead?

This doesn't seem to make sense, because the generated SQL doesn't include a subquery. But indeed the result isn't sorted:

result[1:5]
#> [1] "WY0050091" "IL0034592" "WVG414531" "VAG110338" "WVG415225"

If I submit the above SQL to Postgres directly using pool::dbGetQuery(), without using dbplyr, it works as expected:

result <- pool::dbGetQuery(dbpool, 
'SELECT DISTINCT "external_permit_nmbr" FROM echo_dfr.x_cwa_limits ORDER BY "external_permit_nmbr"')

The result is sorted, and I don't get a warning.

I just verified that I get the same warning when the database driver is odbc::odbc(), although the generated SQL is slightly different (table name is in parentheses):

dplyr::show_query(query)
#> <SQL>
#> SELECT DISTINCT "EXTERNAL_PERMIT_NMBR"
#> FROM (echo_dfr.x_cwa_limits) 
#> ORDER BY "EXTERNAL_PERMIT_NMBR"
result <- dplyr::pull(query)
#> Warning: ORDER BY is ignored in subqueries without LIMIT
#> i Do you need to move arrange() later in the pipeline or use window_order() instead?

Could you please make a reprex, following the advice in https://dbplyr.tidyverse.org/articles/reprex.html?

Ok, here's a reprex:

library(dbplyr)
library(dplyr, warn.conflicts = FALSE)

con <- DBI::dbConnect(RPostgres::Postgres(),
  dbname = "test",
  host = "localhost",
  user = ""
)

db <- copy_to(con, data.frame(x = 1:2), "test")

db2 <- db %>% 
  select(x) %>% 
  distinct() %>% 
  arrange(x)

db2 %>% collect()
#> # A tibble: 2 x 1
#>       x
#>   <int>
#> 1     1
#> 2     2
db2 %>% pull()
#> Warning: ORDER BY is ignored in subqueries without LIMIT
#> ℹ Do you need to move arrange() later in the pipeline or use window_order() instead?
#> [1] 1 2

^{Created on 2021-01-21 by the reprex package (v0.3.0.9001)}

The problem seems to be specifically with pull()

And the problem is that pull() itself does a select to ensure that you're only retrieving a single column. I think the easiest fix is for pull() not to do that additional select when there's already only one column in the result.

Fixed in e2c383a

Wow. Thanks. I was going to find time today to make a reprex...

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"ORDER BY is ignored in subqueries without LIMIT" without a subquery #562

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"ORDER BY is ignored in subqueries without LIMIT" without a subquery #562

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andrew-schulman commented on Dec 15, 2020

hadley commented on Jan 19, 2021

hadley commented on Jan 21, 2021

hadley commented on Jan 21, 2021

hadley commented on Jan 21, 2021

andrew-schulman commented on Jan 23, 2021

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