From 154eeacd1afcc5720cc17aa31bd75a61d4aa885e Mon Sep 17 00:00:00 2001
From: Daniel Possenriede <possenriede@gmail.com>
Date: Fri, 2 Apr 2021 12:28:20 +0200
Subject: [PATCH] add pqListTables()

---
 DESCRIPTION         |  1 +
 NAMESPACE           |  2 ++
 R/PqGenerics.R      | 68 +++++++++++++++++++++++++++++++++++++++++++++
 man/pqListTables.Rd | 38 +++++++++++++++++++++++++
 4 files changed, 109 insertions(+)
 create mode 100644 R/PqGenerics.R
 create mode 100644 man/pqListTables.Rd

diff --git a/DESCRIPTION b/DESCRIPTION
index ec946efd..a0caf406 100644
--- a/DESCRIPTION
+++ b/DESCRIPTION
@@ -62,6 +62,7 @@ SystemRequirements: libpq >= 9.0: libpq-dev (deb) or
 Collate: 
     'PqDriver.R'
     'PqConnection.R'
+    'PqGenerics.R'
     'PqResult.R'
     'RPostgres-pkg.R'
     'RcppExports.R'
diff --git a/NAMESPACE b/NAMESPACE
index e0098385..1b5b2671 100644
--- a/NAMESPACE
+++ b/NAMESPACE
@@ -7,6 +7,7 @@ export(Redshift)
 export(postgresDefault)
 export(postgresHasDefault)
 export(postgresWaitForNotify)
+export(pqListTables)
 exportClasses(PqConnection)
 exportClasses(PqDriver)
 exportClasses(PqResult)
@@ -51,6 +52,7 @@ exportMethods(dbUnloadDriver)
 exportMethods(dbUnquoteIdentifier)
 exportMethods(dbWithTransaction)
 exportMethods(dbWriteTable)
+exportMethods(pqListTables)
 exportMethods(show)
 exportMethods(sqlData)
 import(DBI)
diff --git a/R/PqGenerics.R b/R/PqGenerics.R
new file mode 100644
index 00000000..18b88063
--- /dev/null
+++ b/R/PqGenerics.R
@@ -0,0 +1,68 @@
+# PostgreSQL-specific features and functions
+
+#' List remote tables
+#'
+#' Returns the unquoted names of remote tables and table-like objects accessible
+#' through this connection.
+#' This includes foreign and partitioned tables, (materialized) views, as well
+#' as temporary objects.
+#'
+#' @inheritParams postgres-tables
+#'
+#' @family PqConnection generics
+#'
+#' @examples
+#' # For running the examples on systems without PostgreSQL connection:
+#' run <- postgresHasDefault()
+#'
+#' library(DBI)
+#' if (run) con <- dbConnect(RPostgres::Postgres())
+#' if (run) dbListTables(con)
+#'
+#' if (run) dbWriteTable(con, "mtcars", mtcars, temporary = TRUE)
+#' if (run) dbListTables(con)
+#'
+#' if (run) dbDisconnect(con)
+#'
+#' @export
+setGeneric("pqListTables",
+           def = function(conn, ...) standardGeneric("pqListTables"),
+           valueClass = "character"
+)
+
+#' @rdname pqListTables
+#' @export
+setMethod("pqListTables", "PqConnection", function(conn) {
+  major_server_version <- dbGetInfo(conn)$db.version %/% 10000
+
+  query <- paste0(
+    # pg_class docs: https://www.postgresql.org/docs/current/catalog-pg-class.html
+    "SELECT cl.relname AS name FROM pg_class AS cl ",
+    "JOIN pg_namespace AS n ON cl.relnamespace = n.oid ",
+    "WHERE (n.nspname = ANY (current_schemas(true))) ",
+    "AND (n.nspname <> 'pg_catalog') "
+  )
+
+  if (major_server_version >= 10) {
+    # relkind = 'p' and relispartition only supported from v10 onwards
+    query <- paste0(
+      query,
+      # r = ordinary table, v = view, m = materialized view, f = foreign table, p = partitioned table
+      "AND (cl.relkind IN ('r', 'v', 'm', 'f', 'p')) ",
+      "AND NOT cl.relispartition "
+    )
+  } else {
+    query <- paste0(
+      query,
+      "AND (cl.relkind IN ('r', 'v', 'm', 'f')) "
+    )
+  }
+
+  query <- paste0(
+    query,
+    "ORDER BY name"
+  )
+
+  dbGetQuery(conn, query)[[1]]
+})
+
diff --git a/man/pqListTables.Rd b/man/pqListTables.Rd
new file mode 100644
index 00000000..e58bf76e
--- /dev/null
+++ b/man/pqListTables.Rd
@@ -0,0 +1,38 @@
+% Generated by roxygen2: do not edit by hand
+% Please edit documentation in R/PqGenerics.R
+\name{pqListTables}
+\alias{pqListTables}
+\alias{pqListTables,PqConnection-method}
+\title{List remote tables}
+\usage{
+pqListTables(conn, ...)
+
+\S4method{pqListTables}{PqConnection}(conn)
+}
+\arguments{
+\item{conn}{a \linkS4class{PqConnection} object, produced by
+\code{\link[DBI:dbConnect]{DBI::dbConnect()}}}
+
+\item{...}{Ignored.}
+}
+\description{
+Returns the unquoted names of remote tables and table-like objects accessible
+through this connection.
+This includes foreign and partitioned tables, (materialized) views, as well
+as temporary objects.
+}
+\examples{
+# For running the examples on systems without PostgreSQL connection:
+run <- postgresHasDefault()
+
+library(DBI)
+if (run) con <- dbConnect(RPostgres::Postgres())
+if (run) dbListTables(con)
+
+if (run) dbWriteTable(con, "mtcars", mtcars, temporary = TRUE)
+if (run) dbListTables(con)
+
+if (run) dbDisconnect(con)
+
+}
+\concept{PqConnection generics}