Restrict table alias length to avoid truncation

R/lazy-join-query.R

@@ -199,15 +199,26 @@ sql_build.lazy_multi_join_query <- function(op, con, ...) {
 }
 
 generate_join_table_names <- function(table_names) {
+  table_name_length_max <- dplyr::coalesce(max(nchar(table_names$name)), 0)
+
   if (length(table_names$name) != 2) {
     table_names_repaired <- vctrs::vec_as_names(table_names$name, repair = "unique", quiet = TRUE)
     auto_name <- table_names$from != "as"
     table_names$name[auto_name] <- table_names_repaired[auto_name]
-
-    return(table_names$name)
+    table_names_prepared <- table_names$name
+  } else{
+    table_names_prepared <- join_two_table_alias(table_names$name, table_names$from)
   }
 
-  join_two_table_alias(table_names$name, table_names$from)
+  # avoid database aliases exceeding the database-specific maximum length
+  abbreviate(
+    table_names_prepared,
+    # arbitrarily floor at 63 (Postgres limit) to avoid unnecessarily truncating reasonable lengths
+    minlength = max(table_name_length_max, 63),
+    # (explicit, default) err on the side of unique table names instead of exact length
+    strict = FALSE,
+    named = FALSE
+  )
 }
 
 #' @export

tests/testthat/_snaps/verb-joins.md

@@ -40,6 +40,37 @@
       LEFT JOIN `foo2`.`df` AS `df_RHS`
         ON (`df_LHS`.`x` = `df_RHS`.`x`)
 
+# alias truncates long table names at database limit
+
+    Code
+      self_join2 %>% remote_query()
+    Output
+      <SQL> SELECT `a012345678901234567890123456789012345678901234567890123456789012_L`.*
+      FROM `a012345678901234567890123456789012345678901234567890123456789012` AS `a012345678901234567890123456789012345678901234567890123456789012_L`
+      LEFT JOIN `a012345678901234567890123456789012345678901234567890123456789012` AS `a012345678901234567890123456789012345678901234567890123456789012_R`
+        ON (
+          `a012345678901234567890123456789012345678901234567890123456789012_L`.`x` = `a012345678901234567890123456789012345678901234567890123456789012_R`.`x` AND
+          `a012345678901234567890123456789012345678901234567890123456789012_L`.`y` = `a012345678901234567890123456789012345678901234567890123456789012_R`.`y`
+        )
+
+---
+
+    Code
+      self_join3 %>% remote_query()
+    Output
+      <SQL> SELECT
+        `a012345678901234567890123456789012345678901234567890123456789012...1`.`x` AS `x`,
+        `a012345678901234567890123456789012345678901234567890123456789012...1`.`y` AS `y.x`,
+        `b012345678901234567890123456789012345678901234567890123456789012`.`y` AS `y.y`
+      FROM `a012345678901234567890123456789012345678901234567890123456789012` AS `a012345678901234567890123456789012345678901234567890123456789012...1`
+      LEFT JOIN `a012345678901234567890123456789012345678901234567890123456789012` AS `a012345678901234567890123456789012345678901234567890123456789012...2`
+        ON (
+          `a012345678901234567890123456789012345678901234567890123456789012...1`.`x` = `a012345678901234567890123456789012345678901234567890123456789012...2`.`x` AND
+          `a012345678901234567890123456789012345678901234567890123456789012...1`.`y` = `a012345678901234567890123456789012345678901234567890123456789012...2`.`y`
+        )
+      INNER JOIN `b012345678901234567890123456789012345678901234567890123456789012`
+        ON (`a012345678901234567890123456789012345678901234567890123456789012...1`.`x` = `b012345678901234567890123456789012345678901234567890123456789012`.`x`)
+
 # join check `x_as` and `y_as`
 
     Code

tests/testthat/test-verb-joins.R

@@ -72,6 +72,42 @@ test_that("join works with in_schema", {
   )
 })
 
+test_that("alias truncates long table names at database limit", {
+  # Postgres has max table name length of 63; ensure it's not exceeded when generating table alias
+  withr::local_db_connection(con <- dbConnect(RSQLite::SQLite(), ":memory:"))
+
+  nm1 <- paste0("a", paste0(0:62 %% 10, collapse = ""))
+  DBI::dbWriteTable(con, nm1, tibble(x = 1:3, y = "a"))
+  mf1 <- tbl(con, nm1)
+
+  nm2 <- paste0("b", paste0(0:62 %% 10, collapse = ""))
+  DBI::dbWriteTable(con, nm2, tibble(x = 2:3, y = "b"))
+  mf2 <- tbl(con, nm2)
+
+  # 2 tables
+  self_join2 <- left_join(mf1, mf1, by = c("x", "y"))
+
+  expect_equal(
+    self_join2 %>% collect(),
+    tibble(x = 1:3, y = "a")
+  )
+  expect_snapshot(
+    self_join2 %>% remote_query()
+  )
+
+  # 3 tables
+  self_join3 <- left_join(mf1, mf1, by = c("x", "y")) %>%
+    inner_join(mf2, by = "x")
+
+  expect_equal(
+    self_join3 %>% collect(),
+    tibble(x = 2:3, y.x = "a", y.y = "b")
+  )
+  expect_snapshot(
+    self_join3 %>% remote_query()
+  )
+})
+
 test_that("joins with non by variables gives cross join", {
   df1 <- memdb_frame(x = 1:5)
   df2 <- memdb_frame(y = 1:5)