feat: Importing large objects from client side #472
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@@ -135,3 +135,38 @@ postgresWaitForNotify <- function(conn, timeout = 1) { | |
| postgresIsTransacting <- function(conn) { | ||
| connection_is_transacting(conn@ptr) | ||
| } | ||
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| #' 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 | ||
| #' con <- postgresDefault() | ||
| #' path_to_file <- 'my_image.png' | ||
| #' dbWithTransaction(con, { | ||
| #' oid <- postgresImportLargeObject(con, test_file_path) | ||
| #' }) | ||
| postgresImportLargeObject <- function(conn, filepath = NULL, oid = 0) { | ||
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| if (!postgresIsTransacting(conn)) { | ||
| stopc("Cannot import a large object outside of a transaction") | ||
| } | ||
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| if (is.null(filepath)) stopc("'filepath' cannot be NULL") | ||
| if (oid < 0) stopc("'oid' cannot be negative") | ||
| if (is.null(oid) | is.na(oid)) stopc("'oid' cannot be NULL/NA") | ||
| if (file.access(filepath,4) == -1) stopc(paste0("Unable to read from filepath '",filepath,"'")) | ||
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There was a problem hiding this comment. What will the error look like if we let libpq do the check?
There was a problem hiding this comment. libpq returns an InvalidOid (a zero). Letting libpq do the check has the downside that we cannot inform the user of the specific problem as libpq's So currently if the accessibility of the file has changed, an error is thrown with the message There was a problem hiding this comment. I see:
Would that work well enough? Also: how do we auto-assign the OID? There was a problem hiding this comment. Thanks! I was unaware of
(It's a bit clunky as the term "error" is repeated, but informative nonetheless.) pqlib auto-assigns the oid if the argument 'oid' is zero. From the docs:
I also changed the return- and argument types to 'Oid' from int as oid's are implemented as unsigned integers. |
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| 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) | ||
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| } | ||
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| #include <cpp11.hpp> | ||
| #include <libpq-fe.h> | ||
| #include <libpq/libpq-fs.h> | ||
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| #include <plogr.h> | ||
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| postgres |
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| 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) | ||
| }) | ||
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| 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) }) | ||
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| expect_error( | ||
| dbWithTransaction(con, { oid <- postgresImportLargeObject(con, test_file_path, oid) }) | ||
| ) | ||
| dbExecute(con, "select lo_unlink($1) as lo_data", params=list(oid)) | ||
| }) | ||
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| 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) }) | ||
| ) | ||
| }) | ||
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Or perhaps this could be two checks?