Discussion: https://postgr.es/m/CAPpHfdua-YFw3XTprfutzGp28xXLigFtzNbuFY8yPhqeq6X5kg%40mail.gmail.com
Reviewed-by: Aleksander Alekseev, Pavel Borisov, Vignesh C, Mason Sharp
Reviewed-by: Andres Freund, Chris Travers

Author: Andres Freund
Reviewed-by: Pavel Borisov
Discussion: https://www.postgresql.org/message-id/flat/CAPpHfdua-YFw3XTprfutzGp28xXLigFtzNbuFY8yPhqeq6X5kg%40mail.gmail.com

Snapshot have two pairing heap nodes: for data and system undos.

 * Added SearchCatCacheInternal_hook, SearchCatCacheList_hook
 * Added SysCacheGetAttr_hook

IsFatalError()
have_backup_in_progress()
SnapBuildNextPhaseAt()
DoLocalLockExist()

…ining

a lock.

Outline-atomics is a gcc compilation flag that enables runtime detection
of CPU support for atomic instructions.
Performance on CPUs that do support atomic instructions is improved,
while compatibility and performance on CPUs without atomic instructions
is not hurt.

Discussion: https://postgr.es/m/flat/099F69EE-51D3-4214-934A-1F28C0A1A7A7%40amazon.com
Author: Tsahi Zidenberg

They are allowed to stay during shutdown checkpointing and help checkpointer
do its work.

…ecks

To use curl during shared_preload_libraries initialization.

- added option --extension for pg_rewind
- extracted SimpleXLogRead from extractPageMap for generic wal iteration in pg_rewind

Also validates compatability of index AM with table AM at index creation

…on_info

 * Add xlogptr and xmin to determine right order of transactions when
   decoding on replica.
 * Add CSN snapshot data to snapshot builder.
 * Record CSN to the running xids and restore it during logical decoding
   to the snapshot builder.
 * Add function to update CSN snapshot data in snapshot builder.
 * Update CSN snapshot LSN in snapshot building after each transaction commit.
 * Restore CSN snapshot data in SnapBuildBuildSnapshot().

That allows S3 mode to finish WAL archiving if needed.

That allows to process flushed buffers in CheckPoint_hook().

Use GetIndexAmRoutineExtended instead for all Orioledb extensibility.

We split aminsert method to aminsert and aminsertextended.

aminsert is a method for indexes implemented in other extensions, it
accepts ItemPointer tupleid.

aminsertextended is for internal Postgres indexes and Orioledb, it
accepts Datum tupleid. They are not supposed to call aminsert method, so
that it is set NULL for them. We can not rely that extensions are aware
of aminsertextended, so index_insert() calls aminsert if it's not NULL
preferentially.

Signature of index_insert() is reverted so that it could be called by other
extensions. Datum tupleid is confined inside index_insert method.

It's the same approach done in configure.ac.