Add SUMMARIZE incremental backup mode using PG 17+ WAL summarize feature

[heysky]

This commit adds a new incremental backup mode called SUMMARIZE that leverages PostgreSQL 17+'s native WAL summarize feature (summarize_wal GUC) to track modified data blocks without requiring external extensions like ptrack.

Feature Overview

The SUMMARIZE backup mode:

• Requires PostgreSQL 17+ with summarize_wal=on enabled
• Uses pg_wal_summary_contents() and pg_available_wal_summaries() functions
• Builds pagemap bitmaps from WAL summary information for incremental backups
• Validates WAL summary availability before backup starts

Files Modified

• src/pg_probackup.h: Added BACKUP_MODE_DIFF_SUMMARIZE enum and function declarations
• src/catalog.c: Updated backupModes[] array and mode parsing functions
• src/validate.c: Added SUMMARIZE mode to validation checks
• src/backup.c: Added WAL summary LSN validation and wait logic
• src/data.c: Added SUMMARIZE mode to incremental mode checks
• src/catchup.c: Added WAL summarize support for catchup command
• src/pg_probackup.c: Added SUMMARIZE to supported backup modes
• src/help.c: Updated help text to include SUMMARIZE mode
• Makefile: Added src/walsummary.o to object files list

New File

• src/walsummary.c: Core implementation of WAL summary integration
  • pg_is_walsummary_enabled(): Check if PG 17+ has summarize_wal enabled
  • get_walsummary_summarized_lsn(): Get current summarized LSN
  • wait_wal_summarization(): Wait for summarizer to catch up to target LSN (60s timeout)
  • make_pagemap_from_walsummary(): Build pagemap from WAL summary data

Key Implementation Details

Function Integration

The make_pagemap_from_walsummary() function:

1. Queries pg_available_wal_summaries() to find overlapping summary files
2. For each summary, calls pg_wal_summary_contents() with intersection range
3. Builds pagemap bitmaps for changed blocks
4. Matches WAL summary data to pgFile list using (dbOid, tblspcOid, relOid, forkName)

Usage

Create incremental backup with SUMMARIZE mode:
pg_probackup backup -B /backup/dir -b SUMMARIZE --instance=name -D /data/dir

Prerequisites:

• PostgreSQL 17 or higher
• summarize_wal=on in postgresql.conf
• Previous FULL backup exists

Error Handling

If WAL summarizer is disabled:
ERROR: WAL summarize backup mode requires summarize_wal to be enabled

If summarizer doesn't catch up within 60 seconds:
ERROR: WAL summarizer did not catch up to within timeout period. Incremental backup cannot proceed without complete WAL summaries.

[demonolock]

@heysky Thank you for you contrib. I left comments that may improve it. Please take a look. Also the target branch should be REL_2_5, not master.

[heysky]

@heysky Thank you for you contrib. I left comments that may improve it. Please take a look. Also the target branch should be REL_2_5, not master.

@demonolock Victoria, I've made the changes based on your feedback. Please review when you have a chance. It looks like that I cannot change the target brach directly on this PR. Shall I raise another PR based on branch REL_2_5 instead?