Revert 0f5ca02f53

0f5ca02f53 introduces 3 new keywords.  It appears to be too much for relatively
small feature.  Given now we past feature freeze, it's already late for
discussion of the new syntax.  So, revert.

Discussion: https://postgr.es/m/28209.1586294824%40sss.pgh.pa.us

2 files changed, 1 insertions, 297 deletions

diff --git a/src/backend/commands/Makefile b/src/backend/commands/Makefile
index 9b310926c12..d4815d3ce65 100644
--- a/src/backend/commands/Makefile
+++ b/src/backend/commands/Makefile
@@ -57,7 +57,6 @@ OBJS = \
 	user.o \
 	vacuum.o \
 	variable.o \
-	view.o \
-	wait.o
+	view.o
 
 include $(top_srcdir)/src/backend/common.mk
diff --git a/src/backend/commands/wait.c b/src/backend/commands/wait.c
deleted file mode 100644
index b7aee5b794b..00000000000
--- a/src/backend/commands/wait.c
+++ /dev/null
@@ -1,295 +0,0 @@
-/*-------------------------------------------------------------------------
- *
- * wait.c
- *	  Implements WAIT FOR clause for BEGIN and START TRANSACTION commands.
- *	  This clause allows waiting for given LSN to be replayed on standby.
- *
- * Copyright (c) 2020, PostgreSQL Global Development Group
- *
- * IDENTIFICATION
- *	  src/backend/commands/wait.c
- *
- *-------------------------------------------------------------------------
- */
-#include "postgres.h"
-
-#include <math.h>
-
-#include "access/xlog.h"
-#include "access/xlogdefs.h"
-#include "commands/wait.h"
-#include "funcapi.h"
-#include "miscadmin.h"
-#include "pgstat.h"
-#include "storage/backendid.h"
-#include "storage/pmsignal.h"
-#include "storage/proc.h"
-#include "storage/shmem.h"
-#include "storage/sinvaladt.h"
-#include "storage/spin.h"
-#include "utils/builtins.h"
-#include "utils/pg_lsn.h"
-#include "utils/timestamp.h"
-
-/*
- * Shared memory structure representing information about LSNs, which backends
- * are waiting for replay.
- */
-typedef struct
-{
-	slock_t		mutex;			/* mutex protecting the fields below */
-	int			max_backend_id; /* max backend_id present in lsns[] */
-	pg_atomic_uint64 min_lsn;	/* minimal waited LSN */
-	/* per-backend array of waited LSNs */
-	XLogRecPtr	lsns[FLEXIBLE_ARRAY_MEMBER];
-}			WaitLSNState;
-
-static WaitLSNState * state;
-
-/*
- * Add the wait event of the current backend to shared memory array
- */
-static void
-WaitLSNAdd(XLogRecPtr lsn_to_wait)
-{
-	SpinLockAcquire(&state->mutex);
-	if (state->max_backend_id < MyBackendId)
-		state->max_backend_id = MyBackendId;
-
-	state->lsns[MyBackendId] = lsn_to_wait;
-
-	if (lsn_to_wait < state->min_lsn.value)
-		state->min_lsn.value = lsn_to_wait;
-	SpinLockRelease(&state->mutex);
-}
-
-/*
- * Delete wait event of the current backend from the shared memory array.
- */
-void
-WaitLSNDelete(void)
-{
-	int			i;
-	XLogRecPtr	deleted_lsn;
-
-	SpinLockAcquire(&state->mutex);
-
-	deleted_lsn = state->lsns[MyBackendId];
-	state->lsns[MyBackendId] = InvalidXLogRecPtr;
-
-	/* If we are deleting the minimal LSN, then choose the next min_lsn */
-	if (!XLogRecPtrIsInvalid(deleted_lsn) &&
-		deleted_lsn == state->min_lsn.value)
-	{
-		state->min_lsn.value = InvalidXLogRecPtr;
-		for (i = 2; i <= state->max_backend_id; i++)
-		{
-			if (!XLogRecPtrIsInvalid(state->lsns[i]) &&
-				(state->lsns[i] < state->min_lsn.value ||
-				 XLogRecPtrIsInvalid(state->min_lsn.value)))
-			{
-				state->min_lsn.value = state->lsns[i];
-			}
-		}
-	}
-
-	/* If deleting from the end of the array, shorten the array's used part */
-	if (state->max_backend_id == MyBackendId)
-	{
-		for (i = (MyBackendId); i >= 2; i--)
-			if (!XLogRecPtrIsInvalid(state->lsns[i]))
-			{
-				state->max_backend_id = i;
-				break;
-			}
-	}
-
-	SpinLockRelease(&state->mutex);
-}
-
-/*
- * Report amount of shared memory space needed for WaitLSNState
- */
-Size
-WaitLSNShmemSize(void)
-{
-	Size		size;
-
-	size = offsetof(WaitLSNState, lsns);
-	size = add_size(size, mul_size(MaxBackends + 1, sizeof(XLogRecPtr)));
-	return size;
-}
-
-/*
- * Initialize an shared memory structure for waiting for LSN
- */
-void
-WaitLSNShmemInit(void)
-{
-	bool		found;
-	uint32		i;
-
-	state = (WaitLSNState *) ShmemInitStruct("pg_wait_lsn",
-											 WaitLSNShmemSize(),
-											 &found);
-	if (!found)
-	{
-		SpinLockInit(&state->mutex);
-
-		for (i = 0; i < (MaxBackends + 1); i++)
-			state->lsns[i] = InvalidXLogRecPtr;
-
-		state->max_backend_id = 0;
-		pg_atomic_init_u64(&state->min_lsn, InvalidXLogRecPtr);
-	}
-}
-
-/*
- * Set latches in shared memory to signal that new LSN has been replayed
- */
-void
-WaitLSNSetLatch(XLogRecPtr cur_lsn)
-{
-	uint32		i;
-	int			max_backend_id;
-	PGPROC	   *backend;
-
-	SpinLockAcquire(&state->mutex);
-	max_backend_id = state->max_backend_id;
-
-	for (i = 2; i <= max_backend_id; i++)
-	{
-		backend = BackendIdGetProc(i);
-
-		if (backend && state->lsns[i] != 0 &&
-			state->lsns[i] <= cur_lsn)
-		{
-			SetLatch(&backend->procLatch);
-		}
-	}
-	SpinLockRelease(&state->mutex);
-}
-
-/*
- * Get minimal LSN that some backend is waiting for
- */
-XLogRecPtr
-WaitLSNGetMin(void)
-{
-	return state->min_lsn.value;
-}
-
-/*
- * On WAIT use a latch to wait till LSN is replayed, postmaster dies or timeout
- * happens. Timeout is specified in milliseconds.  Returns true if LSN was
- * reached and false otherwise.
- */
-bool
-WaitLSNUtility(XLogRecPtr target_lsn, const int timeout_ms)
-{
-	XLogRecPtr	cur_lsn;
-	int			latch_events;
-	float8		endtime;
-	bool		res = false;
-	bool		wait_forever = (timeout_ms <= 0);
-
-	endtime = GetNowFloat() + timeout_ms / 1000.0;
-
-	latch_events = WL_LATCH_SET | WL_TIMEOUT | WL_EXIT_ON_PM_DEATH;
-
-	/* Check if we already reached the needed LSN */
-	cur_lsn = GetXLogReplayRecPtr(NULL);
-	if (cur_lsn >= target_lsn)
-		return true;
-
-	WaitLSNAdd(target_lsn);
-	ResetLatch(MyLatch);
-
-	/* Recheck if LSN was reached while WaitLSNAdd() and ResetLatch() */
-	cur_lsn = GetXLogReplayRecPtr(NULL);
-	if (cur_lsn >= target_lsn)
-		return true;
-
-	for (;;)
-	{
-		int			rc;
-		float8		time_left = 0;
-		long		time_left_ms = 0;
-
-		time_left = endtime - GetNowFloat();
-
-		/* Use 1 second as the default timeout to check for interrupts */
-		if (wait_forever || time_left < 0 || time_left > 1.0)
-			time_left_ms = 1000;
-		else
-			time_left_ms = (long) ceil(time_left * 1000.0);
-
-		/* If interrupt, LockErrorCleanup() will do WaitLSNDelete() for us */
-		CHECK_FOR_INTERRUPTS();
-
-		/* If postmaster dies, finish immediately */
-		if (!PostmasterIsAlive())
-			break;
-
-		rc = WaitLatch(MyLatch, latch_events, time_left_ms,
-					   WAIT_EVENT_CLIENT_READ);
-
-		ResetLatch(MyLatch);
-
-		if (rc & WL_LATCH_SET)
-			cur_lsn = GetXLogReplayRecPtr(NULL);
-
-		if (rc & WL_TIMEOUT)
-		{
-			time_left = endtime - GetNowFloat();
-			/* If the time specified by user has passed, stop waiting */
-			if (!wait_forever && time_left <= 0.0)
-				break;
-			cur_lsn = GetXLogReplayRecPtr(NULL);
-		}
-
-		/* If LSN has been replayed */
-		if (target_lsn <= cur_lsn)
-			break;
-	}
-
-	WaitLSNDelete();
-
-	if (cur_lsn < target_lsn)
-		ereport(WARNING,
-				(errcode(ERRCODE_IN_FAILED_SQL_TRANSACTION),
-				 errmsg("didn't start transaction because LSN was not reached"),
-				 errhint("Try to increase wait timeout.")));
-	else
-		res = true;
-
-	return res;
-}
-
-/*
- * Implementation of WAIT FOR clause for BEGIN and START TRANSACTION commands
- */
-int
-WaitLSNMain(WaitClause *stmt, DestReceiver *dest)
-{
-	TupleDesc	tupdesc;
-	TupOutputState *tstate;
-	XLogRecPtr	target_lsn;
-	bool		res = false;
-
-	target_lsn = DatumGetLSN(DirectFunctionCall1(pg_lsn_in,
-												 CStringGetDatum(stmt->lsn)));
-	res = WaitLSNUtility(target_lsn, stmt->timeout);
-
-	/* Need a tuple descriptor representing a single TEXT column */
-	tupdesc = CreateTemplateTupleDesc(1);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 1, "LSN reached", TEXTOID, -1, 0);
-
-	/* Prepare for projection of tuples */
-	tstate = begin_tup_output_tupdesc(dest, tupdesc, &TTSOpsMinimalTuple);
-
-	/* Send the result */
-	do_text_output_oneline(tstate, res ? "t" : "f");
-	end_tup_output(tstate);
-	return res;
-}