From cd4adf2105028a44527fe3fbbea65153de8d8a4c Mon Sep 17 00:00:00 2001 From: Amul Sul Date: Thu, 26 Jun 2025 11:42:53 +0530 Subject: [PATCH v10 2/8] Refactor: pg_waldump: Separate logic used to calculate the required read size. This refactoring prepares the codebase for an upcoming patch that will support reading WAL from tar files. The logic for calculating the required read size has been updated to handle both normal WAL files and WAL files located inside a tar archive. --- src/bin/pg_waldump/pg_waldump.c | 46 +++++++++++++++++++++++---------- 1 file changed, 33 insertions(+), 13 deletions(-) diff --git a/src/bin/pg_waldump/pg_waldump.c b/src/bin/pg_waldump/pg_waldump.c index 0a0e9b7caaf..a33fc28b9d5 100644 --- a/src/bin/pg_waldump/pg_waldump.c +++ b/src/bin/pg_waldump/pg_waldump.c @@ -327,6 +327,35 @@ identify_target_directory(char *directory, char *fname) return NULL; /* not reached */ } +/* + * Returns the size in bytes of the data to be read. Returns -1 if the end + * point has already been reached. + */ +static inline int +required_read_len(XLogDumpPrivate *private, XLogRecPtr targetPagePtr, + int reqLen) +{ + int count = XLOG_BLCKSZ; + + if (unlikely(private->endptr_reached)) + return -1; + + if (XLogRecPtrIsValid(private->endptr)) + { + if (targetPagePtr + XLOG_BLCKSZ <= private->endptr) + count = XLOG_BLCKSZ; + else if (targetPagePtr + reqLen <= private->endptr) + count = private->endptr - targetPagePtr; + else + { + private->endptr_reached = true; + return -1; + } + } + + return count; +} + /* pg_waldump's XLogReaderRoutine->segment_open callback */ static void WALDumpOpenSegment(XLogReaderState *state, XLogSegNo nextSegNo, @@ -384,21 +413,12 @@ WALDumpReadPage(XLogReaderState *state, XLogRecPtr targetPagePtr, int reqLen, XLogRecPtr targetPtr, char *readBuff) { XLogDumpPrivate *private = state->private_data; - int count = XLOG_BLCKSZ; + int count = required_read_len(private, targetPagePtr, reqLen); WALReadError errinfo; - if (XLogRecPtrIsValid(private->endptr)) - { - if (targetPagePtr + XLOG_BLCKSZ <= private->endptr) - count = XLOG_BLCKSZ; - else if (targetPagePtr + reqLen <= private->endptr) - count = private->endptr - targetPagePtr; - else - { - private->endptr_reached = true; - return -1; - } - } + /* Bail out if the count to be read is not valid */ + if (count < 0) + return -1; if (!WALRead(state, readBuff, targetPagePtr, count, private->timeline, &errinfo)) -- 2.47.1