From 447cf2f8e9dcf9fd89c935f2daee13326a91630a Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Fri, 17 Jul 2020 12:14:28 -0400 Subject: [PATCH] Remove manual tracking of file position in pg_dump/pg_backup_custom.c. We do not really need to track the file position by hand. We were already relying on ftello() whenever the archive file is seekable, while if it's not seekable we don't need the file position info anyway because we're not going to be able to re-write the TOC. Moreover, that tracking was buggy since it failed to account for the effects of fseeko(). Somewhat remarkably, that seems not to have made for any live bugs up to now. We could fix the oversights, but it seems better to just get rid of the whole error-prone mess. In itself this is merely code cleanup. However, it's necessary infrastructure for an upcoming bug-fix patch (because that code *does* need valid file position after fseeko). The bug fix needs to go back as far as v12; hence, back-patch that far. Discussion: https://postgr.es/m/CALBH9DDuJ+scZc4MEvw5uO-=vRyR2=QF9+Yh=3hPEnKHWfS81A@mail.gmail.com --- src/bin/pg_dump/pg_backup_custom.c | 53 ++++++++---------------------- 1 file changed, 14 insertions(+), 39 deletions(-) diff --git a/src/bin/pg_dump/pg_backup_custom.c b/src/bin/pg_dump/pg_backup_custom.c index 369dcea429..2a88e89c19 100644 --- a/src/bin/pg_dump/pg_backup_custom.c +++ b/src/bin/pg_dump/pg_backup_custom.c @@ -70,14 +70,12 @@ typedef struct { CompressorState *cs; int hasSeek; - pgoff_t filePos; - pgoff_t dataStart; } lclContext; typedef struct { int dataState; - pgoff_t dataPos; + pgoff_t dataPos; /* valid only if dataState=K_OFFSET_POS_SET */ } lclTocEntry; @@ -144,8 +142,6 @@ InitArchiveFmt_Custom(ArchiveHandle *AH) AH->lo_buf_size = LOBBUFSIZE; AH->lo_buf = (void *) pg_malloc(LOBBUFSIZE); - ctx->filePos = 0; - /* * Now open the file */ @@ -185,7 +181,6 @@ InitArchiveFmt_Custom(ArchiveHandle *AH) ReadHead(AH); ReadToc(AH); - ctx->dataStart = _getFilePos(AH, ctx); } } @@ -291,7 +286,8 @@ _StartData(ArchiveHandle *AH, TocEntry *te) lclTocEntry *tctx = (lclTocEntry *) te->formatData; tctx->dataPos = _getFilePos(AH, ctx); - tctx->dataState = K_OFFSET_POS_SET; + if (tctx->dataPos >= 0) + tctx->dataState = K_OFFSET_POS_SET; _WriteByte(AH, BLK_DATA); /* Block type */ WriteInt(AH, te->dumpId); /* For sanity check */ @@ -352,7 +348,8 @@ _StartBlobs(ArchiveHandle *AH, TocEntry *te) lclTocEntry *tctx = (lclTocEntry *) te->formatData; tctx->dataPos = _getFilePos(AH, ctx); - tctx->dataState = K_OFFSET_POS_SET; + if (tctx->dataPos >= 0) + tctx->dataState = K_OFFSET_POS_SET; _WriteByte(AH, BLK_BLOBS); /* Block type */ WriteInt(AH, te->dumpId); /* For sanity check */ @@ -553,7 +550,6 @@ _skipBlobs(ArchiveHandle *AH) static void _skipData(ArchiveHandle *AH) { - lclContext *ctx = (lclContext *) AH->formatData; size_t blkLen; char *buf = NULL; int buflen = 0; @@ -577,8 +573,6 @@ _skipData(ArchiveHandle *AH) fatal("could not read from input file: %m"); } - ctx->filePos += blkLen; - blkLen = ReadInt(AH); } @@ -596,12 +590,10 @@ _skipData(ArchiveHandle *AH) static int _WriteByte(ArchiveHandle *AH, const int i) { - lclContext *ctx = (lclContext *) AH->formatData; int res; if ((res = fputc(i, AH->FH)) == EOF) WRITE_ERROR_EXIT; - ctx->filePos += 1; return 1; } @@ -617,13 +609,11 @@ _WriteByte(ArchiveHandle *AH, const int i) static int _ReadByte(ArchiveHandle *AH) { - lclContext *ctx = (lclContext *) AH->formatData; int res; res = getc(AH->FH); if (res == EOF) READ_ERROR_EXIT(AH->FH); - ctx->filePos += 1; return res; } @@ -637,11 +627,8 @@ _ReadByte(ArchiveHandle *AH) static void _WriteBuf(ArchiveHandle *AH, const void *buf, size_t len) { - lclContext *ctx = (lclContext *) AH->formatData; - if (fwrite(buf, 1, len, AH->FH) != len) WRITE_ERROR_EXIT; - ctx->filePos += len; } /* @@ -654,11 +641,8 @@ _WriteBuf(ArchiveHandle *AH, const void *buf, size_t len) static void _ReadBuf(ArchiveHandle *AH, void *buf, size_t len) { - lclContext *ctx = (lclContext *) AH->formatData; - if (fread(buf, 1, len, AH->FH) != len) READ_ERROR_EXIT(AH->FH); - ctx->filePos += len; } /* @@ -690,7 +674,6 @@ _CloseArchive(ArchiveHandle *AH) if (tpos < 0 && ctx->hasSeek) fatal("could not determine seek position in archive file: %m"); WriteToc(AH); - ctx->dataStart = _getFilePos(AH, ctx); WriteDataChunks(AH, NULL); /* @@ -864,30 +847,24 @@ _WorkerJobRestoreCustom(ArchiveHandle *AH, TocEntry *te) /* * Get the current position in the archive file. + * + * With a non-seekable archive file, we may not be able to obtain the + * file position. If so, just return -1. It's not too important in + * that case because we won't be able to rewrite the TOC to fill in + * data block offsets anyway. */ static pgoff_t _getFilePos(ArchiveHandle *AH, lclContext *ctx) { pgoff_t pos; - if (ctx->hasSeek) + pos = ftello(AH->FH); + if (pos < 0) { - /* - * Prior to 1.7 (pg7.3) we relied on the internally maintained - * pointer. Now we rely on ftello() always, unless the file has been - * found to not support it. For debugging purposes, print a warning - * if the internal pointer disagrees, so that we're more likely to - * notice if something's broken about the internal position tracking. - */ - pos = ftello(AH->FH); - if (pos < 0) + /* Not expected if we found we can seek. */ + if (ctx->hasSeek) fatal("could not determine seek position in archive file: %m"); - - if (pos != ctx->filePos) - pg_log_warning("ftell mismatch with expected position -- ftell used"); } - else - pos = ctx->filePos; return pos; } @@ -899,7 +876,6 @@ _getFilePos(ArchiveHandle *AH, lclContext *ctx) static void _readBlockHeader(ArchiveHandle *AH, int *type, int *id) { - lclContext *ctx = (lclContext *) AH->formatData; int byt; /* @@ -920,7 +896,6 @@ _readBlockHeader(ArchiveHandle *AH, int *type, int *id) *id = 0; /* don't return an uninitialized value */ return; } - ctx->filePos += 1; } *id = ReadInt(AH);