Use private (session-specific) temporary tables in Oracle

NAMESPACE

@@ -60,6 +60,8 @@ S3method(db_supports_table_alias_with_as,TestConnection)
 S3method(db_table_temporary,"Microsoft SQL Server")
 S3method(db_table_temporary,DBIConnection)
 S3method(db_table_temporary,HDB)
+S3method(db_table_temporary,OraConnection)
+S3method(db_table_temporary,Oracle)
 S3method(dbplyr_as_join_by,character)
 S3method(dbplyr_as_join_by,default)
 S3method(dbplyr_as_join_by,dplyr_join_by)

NEWS.md

@@ -1,5 +1,6 @@
 # dbplyr (development version)
 
+* Oracle temporary tables now use private temporary tables (Oracle 18c+) instead of global temporary tables. This ensures data persists correctly and table names are automatically prefixed with `ORA$PTT_` (#750).
 * CTEs now correctly quote table names when the same query is used multiple times (#1559).
 * New `last_sql()` retrieves the most recent SQL query generated by dbplyr, which is useful for debugging (#1471).
 * Custom translations of functions starting with `.` work (@MichaelChirico, #1529).

R/backend-oracle.R

@@ -203,10 +203,45 @@ sql_table_analyze.Oracle <- function(con, table, ...) {
   sql_glue2(con, "ANALYZE TABLE {.tbl table} COMPUTE STATISTICS")
 }
 
+is_oracle_temporary_table <- function(table, con) {
+  grepl("^ORA\\$PTT_", table_path_name(table, con), ignore.case = TRUE)
+}
+
+#' @export
+db_table_temporary.Oracle <- function(con, table, temporary, ...) {
+  if (!temporary) {
+    list(table = table, temporary = FALSE)
+  } else if (!is_oracle_temporary_table(table, con)) {
+    new_name <- paste0("ORA$PTT_", table_path_name(table, con))
+    cli::cli_inform(
+      paste0("Created a temporary table named ", new_name),
+      class = c("dbplyr_message_temp_table", "dbplyr_message")
+    )
+    list(table = table_path(new_name), temporary = FALSE)
+  } else {
+    list(table = table, temporary = FALSE)
+  }
+}
+
 #' @export
 sql_query_save.Oracle <- function(con, sql, name, temporary = TRUE, ...) {
-  type <- if (temporary) "GLOBAL TEMPORARY TABLE" else "TABLE"
-  sql_glue2(con, "CREATE {.sql type} {.tbl name} AS\n{sql}")
+  # Since db_table_temporary handles the prefix, `temporary` here is always
+  # FALSE for temp tables (the name already has ORA$PTT_ prefix)
+
+  # ON COMMIT PRESERVE ROWS creates a session-specific temporary table
+  if (is_oracle_temporary_table(name, con)) {
+    sql_glue2(
+      con,
+      "
+      CREATE PRIVATE TEMPORARY TABLE {.tbl name}
+      ON COMMIT PRESERVE ROWS
+      AS
+      {sql}
+      "
+    )
+  } else {
+    sql_glue2(con, "CREATE TABLE {.tbl name} AS\n{sql}")
+  }
 }
 
 #' @export
@@ -253,6 +288,9 @@ sql_query_explain.OraConnection <- sql_query_explain.Oracle
 #' @export
 sql_table_analyze.OraConnection <- sql_table_analyze.Oracle
 
+#' @export
+db_table_temporary.OraConnection <- db_table_temporary.Oracle
+
 #' @export
 sql_query_save.OraConnection <- sql_query_save.Oracle
 

tests/testthat/_snaps/backend-oracle.md

@@ -40,6 +40,13 @@
       RETURNING `df_x`.`a`, `df_x`.`b` AS `b2`
       ;
 
+# db_table_temporary adds ORA$PTT_ prefix
+
+    Code
+      result <- db_table_temporary(con, table_path("tbl"), temporary = TRUE)
+    Message
+      Created a temporary table named ORA$PTT_tbl
+
 # generates custom sql
 
     Code
@@ -69,18 +76,19 @@
 ---
 
     Code
-      sql_query_save(con, sql("SELECT * FROM foo"), in_schema("schema", "tbl"))
+      sql_query_save(con, sql("SELECT * FROM foo"), "ORA$PTT_tbl")
     Output
-      <SQL> CREATE GLOBAL TEMPORARY TABLE `schema`.`tbl` AS
+      <SQL> CREATE PRIVATE TEMPORARY TABLE `ORA$PTT_tbl`
+      ON COMMIT PRESERVE ROWS
+      AS
       SELECT * FROM foo
 
 ---
 
     Code
-      sql_query_save(con, sql("SELECT * FROM foo"), in_schema("schema", "tbl"),
-      temporary = FALSE)
+      sql_query_save(con, sql("SELECT * FROM foo"), "tbl", temporary = FALSE)
     Output
-      <SQL> CREATE TABLE `schema`.`tbl` AS
+      <SQL> CREATE TABLE `tbl` AS
       SELECT * FROM foo
 
 ---

tests/testthat/test-backend-oracle.R

@@ -68,6 +68,27 @@ test_that("`sql_query_upsert()` is correct", {
   )
 })
 
+test_that("db_table_temporary adds ORA$PTT_ prefix", {
+  con <- simulate_oracle()
+
+  # Adds prefix (with message) for temporary tables
+  expect_snapshot(
+    result <- db_table_temporary(con, table_path("tbl"), temporary = TRUE)
+  )
+  expect_equal(as.character(result$table), "ORA$PTT_tbl")
+  expect_false(result$temporary)
+
+  # Doesn't double-prefix if already has ORA$PTT_
+  result <- db_table_temporary(con, table_path("ORA$PTT_tbl"), temporary = TRUE)
+  expect_equal(as.character(result$table), "ORA$PTT_tbl")
+  expect_false(result$temporary)
+
+  # Returns table unchanged for non-temporary
+  result <- db_table_temporary(con, table_path("tbl"), temporary = FALSE)
+  expect_equal(as.character(result$table), "tbl")
+  expect_false(result$temporary)
+})
+
 test_that("generates custom sql", {
   con <- simulate_oracle()
 
@@ -77,15 +98,13 @@ test_that("generates custom sql", {
   lf <- lazy_frame(x = 1, con = con)
   expect_snapshot(left_join(lf, lf, by = "x", na_matches = "na"))
 
+  # With ORA$PTT_ prefix -> creates PRIVATE TEMPORARY TABLE
+  expect_snapshot(sql_query_save(con, sql("SELECT * FROM foo"), "ORA$PTT_tbl"))
+  # Without ORA$PTT_ prefix -> creates regular TABLE
   expect_snapshot(sql_query_save(
     con,
     sql("SELECT * FROM foo"),
-    in_schema("schema", "tbl")
-  ))
-  expect_snapshot(sql_query_save(
-    con,
-    sql("SELECT * FROM foo"),
-    in_schema("schema", "tbl"),
+    "tbl",
     temporary = FALSE
   ))