Hi,
> I think your proposed change is OK, modulo some comments. But I think
> maybe we ought to delete all the stuff related to compressed_bound
> from bbstreamer_lz4_compressor_new() as well, because I don't see that
> there's any point. And then I think we should also add logic similar
> to what you've added here to bbstreamer_lz4_compressor_finalize(), so
> that we're not making the assumption that the buffer will get enlarged
> at some earlier point.
>
> Thoughts?
I agree that we should remove the compression bound stuff from
bbstreamer_lz4_compressor_new() and add a fix in
bbstreamer_lz4_compressor_content() and bbstreamer_lz4_compressor_finalize()
to enlarge the buffer if it falls short of the compress bound.
Patch attached.
Thanks,
Dipesh
From ee9b5e4739bf78b39dc34c9fcc76fc731b09b788 Mon Sep 17 00:00:00 2001
From: Dipesh Pandit <dipesh.pan...@enterprisedb.com>
Date: Thu, 31 Mar 2022 12:19:31 +0530
Subject: [PATCH] fix crash with lz4
We cannot fix the size of output buffer at client during lz4
compression. Client receives chunks from the server and the size of
these chunks varies depending upon the data sent by the server. The
output buffer capacity at client should be adjusted based on the size
of the chunk received from the server.
---
src/bin/pg_basebackup/bbstreamer_lz4.c | 22 ++++++++--------------
1 file changed, 8 insertions(+), 14 deletions(-)
diff --git a/src/bin/pg_basebackup/bbstreamer_lz4.c b/src/bin/pg_basebackup/bbstreamer_lz4.c
index 67f841d..2ffe224 100644
--- a/src/bin/pg_basebackup/bbstreamer_lz4.c
+++ b/src/bin/pg_basebackup/bbstreamer_lz4.c
@@ -73,7 +73,6 @@ bbstreamer_lz4_compressor_new(bbstreamer *next, bc_specification *compress)
bbstreamer_lz4_frame *streamer;
LZ4F_errorCode_t ctxError;
LZ4F_preferences_t *prefs;
- size_t compressed_bound;
Assert(next != NULL);
@@ -92,17 +91,6 @@ bbstreamer_lz4_compressor_new(bbstreamer *next, bc_specification *compress)
if ((compress->options & BACKUP_COMPRESSION_OPTION_LEVEL) != 0)
prefs->compressionLevel = compress->level;
- /*
- * Find out the compression bound, it specifies the minimum destination
- * capacity required in worst case for the success of compression operation
- * (LZ4F_compressUpdate) based on a given source size and preferences.
- */
- compressed_bound = LZ4F_compressBound(streamer->base.bbs_buffer.maxlen, prefs);
-
- /* Enlarge buffer if it falls short of compression bound. */
- if (streamer->base.bbs_buffer.maxlen < compressed_bound)
- enlargeStringInfo(&streamer->base.bbs_buffer, compressed_bound);
-
ctxError = LZ4F_createCompressionContext(&streamer->cctx, LZ4F_VERSION);
if (LZ4F_isError(ctxError))
pg_log_error("could not create lz4 compression context: %s",
@@ -170,7 +158,6 @@ bbstreamer_lz4_compressor_content(bbstreamer *streamer,
* forward the content to next streamer and empty the buffer.
*/
out_bound = LZ4F_compressBound(len, &mystreamer->prefs);
- Assert(mystreamer->base.bbs_buffer.maxlen >= out_bound);
if (avail_out < out_bound)
{
bbstreamer_content(mystreamer->base.bbs_next, member,
@@ -178,6 +165,10 @@ bbstreamer_lz4_compressor_content(bbstreamer *streamer,
mystreamer->bytes_written,
context);
+ /* Enlarge buffer if it falls short of out bound. */
+ if (mystreamer->base.bbs_buffer.maxlen < out_bound)
+ enlargeStringInfo(&mystreamer->base.bbs_buffer, out_bound);
+
avail_out = mystreamer->base.bbs_buffer.maxlen;
mystreamer->bytes_written = 0;
next_out = (uint8 *) mystreamer->base.bbs_buffer.data;
@@ -218,7 +209,6 @@ bbstreamer_lz4_compressor_finalize(bbstreamer *streamer)
/* Find out the footer bound and update the output buffer. */
footer_bound = LZ4F_compressBound(0, &mystreamer->prefs);
- Assert(mystreamer->base.bbs_buffer.maxlen >= footer_bound);
if ((mystreamer->base.bbs_buffer.maxlen - mystreamer->bytes_written) <
footer_bound)
{
@@ -227,6 +217,10 @@ bbstreamer_lz4_compressor_finalize(bbstreamer *streamer)
mystreamer->bytes_written,
BBSTREAMER_UNKNOWN);
+ /* Enlarge buffer if it falls short of footer bound. */
+ if (mystreamer->base.bbs_buffer.maxlen < footer_bound)
+ enlargeStringInfo(&mystreamer->base.bbs_buffer, footer_bound);
+
avail_out = mystreamer->base.bbs_buffer.maxlen;
mystreamer->bytes_written = 0;
next_out = (uint8 *) mystreamer->base.bbs_buffer.data;
--
1.8.3.1
