feat: Importing large objects from client side

NAMESPACE

@@ -6,6 +6,7 @@ export(Postgres)
 export(Redshift)
 export(postgresDefault)
 export(postgresHasDefault)
+export(postgresImportLargeObject)
 export(postgresIsTransacting)
 export(postgresWaitForNotify)
 exportClasses(PqConnection)

R/PqConnection.R

@@ -135,3 +135,41 @@ postgresWaitForNotify <- function(conn, timeout = 1) {
 postgresIsTransacting <- function(conn) {
   connection_is_transacting(conn@ptr)
 }
+
+
+#' Imports a large object from file
+#'
+#' Returns an object idenfier (Oid) for the imported large object
+#'
+#' @export
+#' @param conn a [PqConnection-class] object, produced by
+#'   [DBI::dbConnect()]
+#' @param filepath a path to the large object to import
+#' @param oid the oid to write to. Defaults to 0 which assigns an unused oid
+#' @return the identifier of the large object, an integer
+#' @examples
+#' \dontrun{
+#' con       <- postgresDefault()
+#' filepath <- 'your_image.png'
+#' dbWithTransaction(con, { 
+#'  oid <- postgresImportLargeObject(con, filepath)
+#' })
+#' }
+postgresImportLargeObject <- function(conn, filepath = NULL, oid = 0) {
+
+  if (!postgresIsTransacting(conn)) {
+    stopc("Cannot import a large object outside of a transaction")
+  }
+
+  if (is.null(filepath)) stopc("'filepath' cannot be NULL")
+  if (oid <  0)     stopc("'oid' cannot be negative")
+  if (is.null(oid)) stopc("'oid' cannot be NULL")
+  if (is.na(oid)) stopc("'oid' cannot be NA")
+  if (file.access(filepath,4) == -1) stopc(paste0("Unable to read from filepath '",filepath,"'"))
+
+
+  out_oid = connection_import_lo_from_file(conn@ptr, filepath, oid)
+  if (out_oid == 0) stopc("Import failed. Maybe you tried to write to an existing oid?")
+  return(out_oid)
+
+}

R/cpp11.R

@@ -36,6 +36,10 @@ connection_set_transacting <- function(con, transacting) {
   invisible(.Call(`_RPostgres_connection_set_transacting`, con, transacting))
 }
 
+connection_import_lo_from_file <- function(con, filename, oid) {
+  .Call(`_RPostgres_connection_import_lo_from_file`, con, filename, oid)
+}
+
 connection_copy_data <- function(con, sql, df) {
   invisible(.Call(`_RPostgres_connection_copy_data`, con, sql, df))
 }

_pkgdown.yml

@@ -41,6 +41,7 @@ reference:
   - '`RPostgres-package`'
   - postgresHasDefault
   - postgresWaitForNotify
+  - postgresImportLargeObject
 
 development:
   mode: auto

src/DbConnection.cpp

@@ -128,6 +128,11 @@ bool DbConnection::has_query() {
   return pCurrentResult_ != NULL;
 }
 
+int DbConnection::import_lo_from_file(std::string filename, int p_oid) {
+  Oid lo_oid = lo_import_with_oid(pConn_, filename.c_str(), p_oid);
+  return(lo_oid);
+}
+
 void DbConnection::copy_data(std::string sql, cpp11::list df) {
   LOG_DEBUG << sql;
 

src/DbConnection.h

@@ -35,6 +35,9 @@ class DbConnection : boost::noncopyable {
   bool has_query();
 
   void copy_data(std::string sql, cpp11::list df);
+
+  int  import_lo_from_file(std::string file_path, int p_oid);
+
 
   void check_connection();
   cpp11::list info();

src/connection.cpp

@@ -91,6 +91,10 @@ void connection_set_transacting(DbConnection* con, bool transacting) {
 }
 
 // Specific functions
+[[cpp11::register]]
+int connection_import_lo_from_file(DbConnection* con, std::string filename, int oid) {
+  return con->import_lo_from_file(filename, oid);
+}
 
 [[cpp11::register]]
 void connection_copy_data(DbConnection* con, std::string sql, cpp11::list df) {

src/cpp11.cpp

@@ -71,6 +71,13 @@ extern "C" SEXP _RPostgres_connection_set_transacting(SEXP con, SEXP transacting
   END_CPP11
 }
 // connection.cpp
+int connection_import_lo_from_file(DbConnection* con, std::string filename, int oid);
+extern "C" SEXP _RPostgres_connection_import_lo_from_file(SEXP con, SEXP filename, SEXP oid) {
+  BEGIN_CPP11
+    return cpp11::as_sexp(connection_import_lo_from_file(cpp11::as_cpp<cpp11::decay_t<DbConnection*>>(con), cpp11::as_cpp<cpp11::decay_t<std::string>>(filename), cpp11::as_cpp<cpp11::decay_t<int>>(oid)));
+  END_CPP11
+}
+// connection.cpp
 void connection_copy_data(DbConnection* con, std::string sql, cpp11::list df);
 extern "C" SEXP _RPostgres_connection_copy_data(SEXP con, SEXP sql, SEXP df) {
   BEGIN_CPP11
@@ -197,32 +204,33 @@ extern "C" SEXP _RPostgres_result_column_info(SEXP res) {
 
 extern "C" {
 static const R_CallMethodDef CallEntries[] = {
-    {"_RPostgres_client_version",              (DL_FUNC) &_RPostgres_client_version,              0},
-    {"_RPostgres_connection_copy_data",        (DL_FUNC) &_RPostgres_connection_copy_data,        3},
-    {"_RPostgres_connection_create",           (DL_FUNC) &_RPostgres_connection_create,           3},
-    {"_RPostgres_connection_get_temp_schema",  (DL_FUNC) &_RPostgres_connection_get_temp_schema,  1},
-    {"_RPostgres_connection_info",             (DL_FUNC) &_RPostgres_connection_info,             1},
-    {"_RPostgres_connection_is_transacting",   (DL_FUNC) &_RPostgres_connection_is_transacting,   1},
-    {"_RPostgres_connection_quote_identifier", (DL_FUNC) &_RPostgres_connection_quote_identifier, 2},
-    {"_RPostgres_connection_quote_string",     (DL_FUNC) &_RPostgres_connection_quote_string,     2},
-    {"_RPostgres_connection_release",          (DL_FUNC) &_RPostgres_connection_release,          1},
-    {"_RPostgres_connection_set_temp_schema",  (DL_FUNC) &_RPostgres_connection_set_temp_schema,  2},
-    {"_RPostgres_connection_set_transacting",  (DL_FUNC) &_RPostgres_connection_set_transacting,  2},
-    {"_RPostgres_connection_valid",            (DL_FUNC) &_RPostgres_connection_valid,            1},
-    {"_RPostgres_connection_wait_for_notify",  (DL_FUNC) &_RPostgres_connection_wait_for_notify,  2},
-    {"_RPostgres_encode_data_frame",           (DL_FUNC) &_RPostgres_encode_data_frame,           1},
-    {"_RPostgres_encode_vector",               (DL_FUNC) &_RPostgres_encode_vector,               1},
-    {"_RPostgres_encrypt_password",            (DL_FUNC) &_RPostgres_encrypt_password,            2},
-    {"_RPostgres_init_logging",                (DL_FUNC) &_RPostgres_init_logging,                1},
-    {"_RPostgres_result_bind",                 (DL_FUNC) &_RPostgres_result_bind,                 2},
-    {"_RPostgres_result_column_info",          (DL_FUNC) &_RPostgres_result_column_info,          1},
-    {"_RPostgres_result_create",               (DL_FUNC) &_RPostgres_result_create,               3},
-    {"_RPostgres_result_fetch",                (DL_FUNC) &_RPostgres_result_fetch,                2},
-    {"_RPostgres_result_has_completed",        (DL_FUNC) &_RPostgres_result_has_completed,        1},
-    {"_RPostgres_result_release",              (DL_FUNC) &_RPostgres_result_release,              1},
-    {"_RPostgres_result_rows_affected",        (DL_FUNC) &_RPostgres_result_rows_affected,        1},
-    {"_RPostgres_result_rows_fetched",         (DL_FUNC) &_RPostgres_result_rows_fetched,         1},
-    {"_RPostgres_result_valid",                (DL_FUNC) &_RPostgres_result_valid,                1},
+    {"_RPostgres_client_version",                 (DL_FUNC) &_RPostgres_client_version,                 0},
+    {"_RPostgres_connection_copy_data",           (DL_FUNC) &_RPostgres_connection_copy_data,           3},
+    {"_RPostgres_connection_create",              (DL_FUNC) &_RPostgres_connection_create,              3},
+    {"_RPostgres_connection_get_temp_schema",     (DL_FUNC) &_RPostgres_connection_get_temp_schema,     1},
+    {"_RPostgres_connection_import_lo_from_file", (DL_FUNC) &_RPostgres_connection_import_lo_from_file, 3},
+    {"_RPostgres_connection_info",                (DL_FUNC) &_RPostgres_connection_info,                1},
+    {"_RPostgres_connection_is_transacting",      (DL_FUNC) &_RPostgres_connection_is_transacting,      1},
+    {"_RPostgres_connection_quote_identifier",    (DL_FUNC) &_RPostgres_connection_quote_identifier,    2},
+    {"_RPostgres_connection_quote_string",        (DL_FUNC) &_RPostgres_connection_quote_string,        2},
+    {"_RPostgres_connection_release",             (DL_FUNC) &_RPostgres_connection_release,             1},
+    {"_RPostgres_connection_set_temp_schema",     (DL_FUNC) &_RPostgres_connection_set_temp_schema,     2},
+    {"_RPostgres_connection_set_transacting",     (DL_FUNC) &_RPostgres_connection_set_transacting,     2},
+    {"_RPostgres_connection_valid",               (DL_FUNC) &_RPostgres_connection_valid,               1},
+    {"_RPostgres_connection_wait_for_notify",     (DL_FUNC) &_RPostgres_connection_wait_for_notify,     2},
+    {"_RPostgres_encode_data_frame",              (DL_FUNC) &_RPostgres_encode_data_frame,              1},
+    {"_RPostgres_encode_vector",                  (DL_FUNC) &_RPostgres_encode_vector,                  1},
+    {"_RPostgres_encrypt_password",               (DL_FUNC) &_RPostgres_encrypt_password,               2},
+    {"_RPostgres_init_logging",                   (DL_FUNC) &_RPostgres_init_logging,                   1},
+    {"_RPostgres_result_bind",                    (DL_FUNC) &_RPostgres_result_bind,                    2},
+    {"_RPostgres_result_column_info",             (DL_FUNC) &_RPostgres_result_column_info,             1},
+    {"_RPostgres_result_create",                  (DL_FUNC) &_RPostgres_result_create,                  3},
+    {"_RPostgres_result_fetch",                   (DL_FUNC) &_RPostgres_result_fetch,                   2},
+    {"_RPostgres_result_has_completed",           (DL_FUNC) &_RPostgres_result_has_completed,           1},
+    {"_RPostgres_result_release",                 (DL_FUNC) &_RPostgres_result_release,                 1},
+    {"_RPostgres_result_rows_affected",           (DL_FUNC) &_RPostgres_result_rows_affected,           1},
+    {"_RPostgres_result_rows_fetched",            (DL_FUNC) &_RPostgres_result_rows_fetched,            1},
+    {"_RPostgres_result_valid",                   (DL_FUNC) &_RPostgres_result_valid,                   1},
     {NULL, NULL, 0}
 };
 }

src/pch.h

@@ -1,5 +1,6 @@
 #include <cpp11.hpp>
 #include <libpq-fe.h>
+#include <libpq/libpq-fs.h>
 
 #include <plogr.h>
 

tests/testthat/data/large_object.txt

@@ -0,0 +1 @@
+postgres

tests/testthat/test-ImportLargeObject.R

@@ -0,0 +1,37 @@
+
+test_that("can import and read a large object", {
+  con       <- postgresDefault()
+  on.exit(dbDisconnect(con))
+  test_file_path <- paste0(test_path(),'/data/large_object.txt')
+  dbWithTransaction(con, { oid <- postgresImportLargeObject(con, test_file_path) })
+  expect_gt(oid,0)
+  lo_data           <- unlist(dbGetQuery(con, "select lo_get($1) as lo_data", params=list(oid))$lo_data[1])
+  large_object_txt  <- as.raw(c(0x70, 0x6f, 0x73, 0x74, 0x67, 0x72, 0x65, 0x73)) # the string 'postgres'
+  expect_equal(lo_data, large_object_txt)
+})
+
+
+test_that("importing to an existing oid throws error", {
+  con       <- postgresDefault()
+  on.exit(dbDisconnect(con))
+  test_file_path <- paste0(test_path(),'/data/large_object.txt')
+  oid <- 1234
+  dbWithTransaction(con, { oid <- postgresImportLargeObject(con, test_file_path, oid) })
+
+  expect_error(
+    dbWithTransaction(con, { oid <- postgresImportLargeObject(con, test_file_path, oid) })
+  )
+  dbExecute(con, "select lo_unlink($1) as lo_data", params=list(oid))
+})
+
+
+test_that("import from a non-existing path throws error", {
+  con       <- postgresDefault()
+  on.exit(dbDisconnect(con))
+  test_file_path <- paste0(test_path(),'/data/large_object_that_does_not_exist.txt')
+  expect_error( 
+    dbWithTransaction(con, { oid <- postgresImportLargeObject(con, test_file_path) })
+  )
+})
+
+