Adding upstream version 14.5.upstream/14.5upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1341 insertions, 0 deletions

diff --git a/src/backend/utils/mmgr/mcxt.c b/src/backend/utils/mmgr/mcxt.c
new file mode 100644
index 0000000..a5f31e2
--- /dev/null
+++ b/src/backend/utils/mmgr/mcxt.c
@@ -0,0 +1,1341 @@
+/*-------------------------------------------------------------------------
+ *
+ * mcxt.c
+ *	  POSTGRES memory context management code.
+ *
+ * This module handles context management operations that are independent
+ * of the particular kind of context being operated on.  It calls
+ * context-type-specific operations via the function pointers in a
+ * context's MemoryContextMethods struct.
+ *
+ *
+ * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/utils/mmgr/mcxt.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "mb/pg_wchar.h"
+#include "miscadmin.h"
+#include "storage/proc.h"
+#include "storage/procarray.h"
+#include "storage/procsignal.h"
+#include "utils/fmgrprotos.h"
+#include "utils/memdebug.h"
+#include "utils/memutils.h"
+
+
+/*****************************************************************************
+ *	  GLOBAL MEMORY															 *
+ *****************************************************************************/
+
+/*
+ * CurrentMemoryContext
+ *		Default memory context for allocations.
+ */
+MemoryContext CurrentMemoryContext = NULL;
+
+/*
+ * Standard top-level contexts. For a description of the purpose of each
+ * of these contexts, refer to src/backend/utils/mmgr/README
+ */
+MemoryContext TopMemoryContext = NULL;
+MemoryContext ErrorContext = NULL;
+MemoryContext PostmasterContext = NULL;
+MemoryContext CacheMemoryContext = NULL;
+MemoryContext MessageContext = NULL;
+MemoryContext TopTransactionContext = NULL;
+MemoryContext CurTransactionContext = NULL;
+
+/* This is a transient link to the active portal's memory context: */
+MemoryContext PortalContext = NULL;
+
+static void MemoryContextCallResetCallbacks(MemoryContext context);
+static void MemoryContextStatsInternal(MemoryContext context, int level,
+									   bool print, int max_children,
+									   MemoryContextCounters *totals,
+									   bool print_to_stderr);
+static void MemoryContextStatsPrint(MemoryContext context, void *passthru,
+									const char *stats_string,
+									bool print_to_stderr);
+
+/*
+ * You should not do memory allocations within a critical section, because
+ * an out-of-memory error will be escalated to a PANIC. To enforce that
+ * rule, the allocation functions Assert that.
+ */
+#define AssertNotInCriticalSection(context) \
+	Assert(CritSectionCount == 0 || (context)->allowInCritSection)
+
+
+/*****************************************************************************
+ *	  EXPORTED ROUTINES														 *
+ *****************************************************************************/
+
+
+/*
+ * MemoryContextInit
+ *		Start up the memory-context subsystem.
+ *
+ * This must be called before creating contexts or allocating memory in
+ * contexts.  TopMemoryContext and ErrorContext are initialized here;
+ * other contexts must be created afterwards.
+ *
+ * In normal multi-backend operation, this is called once during
+ * postmaster startup, and not at all by individual backend startup
+ * (since the backends inherit an already-initialized context subsystem
+ * by virtue of being forked off the postmaster).  But in an EXEC_BACKEND
+ * build, each process must do this for itself.
+ *
+ * In a standalone backend this must be called during backend startup.
+ */
+void
+MemoryContextInit(void)
+{
+	AssertState(TopMemoryContext == NULL);
+
+	/*
+	 * First, initialize TopMemoryContext, which is the parent of all others.
+	 */
+	TopMemoryContext = AllocSetContextCreate((MemoryContext) NULL,
+											 "TopMemoryContext",
+											 ALLOCSET_DEFAULT_SIZES);
+
+	/*
+	 * Not having any other place to point CurrentMemoryContext, make it point
+	 * to TopMemoryContext.  Caller should change this soon!
+	 */
+	CurrentMemoryContext = TopMemoryContext;
+
+	/*
+	 * Initialize ErrorContext as an AllocSetContext with slow growth rate ---
+	 * we don't really expect much to be allocated in it. More to the point,
+	 * require it to contain at least 8K at all times. This is the only case
+	 * where retained memory in a context is *essential* --- we want to be
+	 * sure ErrorContext still has some memory even if we've run out
+	 * elsewhere! Also, allow allocations in ErrorContext within a critical
+	 * section. Otherwise a PANIC will cause an assertion failure in the error
+	 * reporting code, before printing out the real cause of the failure.
+	 *
+	 * This should be the last step in this function, as elog.c assumes memory
+	 * management works once ErrorContext is non-null.
+	 */
+	ErrorContext = AllocSetContextCreate(TopMemoryContext,
+										 "ErrorContext",
+										 8 * 1024,
+										 8 * 1024,
+										 8 * 1024);
+	MemoryContextAllowInCriticalSection(ErrorContext, true);
+}
+
+/*
+ * MemoryContextReset
+ *		Release all space allocated within a context and delete all its
+ *		descendant contexts (but not the named context itself).
+ */
+void
+MemoryContextReset(MemoryContext context)
+{
+	AssertArg(MemoryContextIsValid(context));
+
+	/* save a function call in common case where there are no children */
+	if (context->firstchild != NULL)
+		MemoryContextDeleteChildren(context);
+
+	/* save a function call if no pallocs since startup or last reset */
+	if (!context->isReset)
+		MemoryContextResetOnly(context);
+}
+
+/*
+ * MemoryContextResetOnly
+ *		Release all space allocated within a context.
+ *		Nothing is done to the context's descendant contexts.
+ */
+void
+MemoryContextResetOnly(MemoryContext context)
+{
+	AssertArg(MemoryContextIsValid(context));
+
+	/* Nothing to do if no pallocs since startup or last reset */
+	if (!context->isReset)
+	{
+		MemoryContextCallResetCallbacks(context);
+
+		/*
+		 * If context->ident points into the context's memory, it will become
+		 * a dangling pointer.  We could prevent that by setting it to NULL
+		 * here, but that would break valid coding patterns that keep the
+		 * ident elsewhere, e.g. in a parent context.  Another idea is to use
+		 * MemoryContextContains(), but we don't require ident strings to be
+		 * in separately-palloc'd chunks, so that risks false positives.  So
+		 * for now we assume the programmer got it right.
+		 */
+
+		context->methods->reset(context);
+		context->isReset = true;
+		VALGRIND_DESTROY_MEMPOOL(context);
+		VALGRIND_CREATE_MEMPOOL(context, 0, false);
+	}
+}
+
+/*
+ * MemoryContextResetChildren
+ *		Release all space allocated within a context's descendants,
+ *		but don't delete the contexts themselves.  The named context
+ *		itself is not touched.
+ */
+void
+MemoryContextResetChildren(MemoryContext context)
+{
+	MemoryContext child;
+
+	AssertArg(MemoryContextIsValid(context));
+
+	for (child = context->firstchild; child != NULL; child = child->nextchild)
+	{
+		MemoryContextResetChildren(child);
+		MemoryContextResetOnly(child);
+	}
+}
+
+/*
+ * MemoryContextDelete
+ *		Delete a context and its descendants, and release all space
+ *		allocated therein.
+ *
+ * The type-specific delete routine removes all storage for the context,
+ * but we have to recurse to handle the children.
+ * We must also delink the context from its parent, if it has one.
+ */
+void
+MemoryContextDelete(MemoryContext context)
+{
+	AssertArg(MemoryContextIsValid(context));
+	/* We had better not be deleting TopMemoryContext ... */
+	Assert(context != TopMemoryContext);
+	/* And not CurrentMemoryContext, either */
+	Assert(context != CurrentMemoryContext);
+
+	/* save a function call in common case where there are no children */
+	if (context->firstchild != NULL)
+		MemoryContextDeleteChildren(context);
+
+	/*
+	 * It's not entirely clear whether 'tis better to do this before or after
+	 * delinking the context; but an error in a callback will likely result in
+	 * leaking the whole context (if it's not a root context) if we do it
+	 * after, so let's do it before.
+	 */
+	MemoryContextCallResetCallbacks(context);
+
+	/*
+	 * We delink the context from its parent before deleting it, so that if
+	 * there's an error we won't have deleted/busted contexts still attached
+	 * to the context tree.  Better a leak than a crash.
+	 */
+	MemoryContextSetParent(context, NULL);
+
+	/*
+	 * Also reset the context's ident pointer, in case it points into the
+	 * context.  This would only matter if someone tries to get stats on the
+	 * (already unlinked) context, which is unlikely, but let's be safe.
+	 */
+	context->ident = NULL;
+
+	context->methods->delete_context(context);
+
+	VALGRIND_DESTROY_MEMPOOL(context);
+}
+
+/*
+ * MemoryContextDeleteChildren
+ *		Delete all the descendants of the named context and release all
+ *		space allocated therein.  The named context itself is not touched.
+ */
+void
+MemoryContextDeleteChildren(MemoryContext context)
+{
+	AssertArg(MemoryContextIsValid(context));
+
+	/*
+	 * MemoryContextDelete will delink the child from me, so just iterate as
+	 * long as there is a child.
+	 */
+	while (context->firstchild != NULL)
+		MemoryContextDelete(context->firstchild);
+}
+
+/*
+ * MemoryContextRegisterResetCallback
+ *		Register a function to be called before next context reset/delete.
+ *		Such callbacks will be called in reverse order of registration.
+ *
+ * The caller is responsible for allocating a MemoryContextCallback struct
+ * to hold the info about this callback request, and for filling in the
+ * "func" and "arg" fields in the struct to show what function to call with
+ * what argument.  Typically the callback struct should be allocated within
+ * the specified context, since that means it will automatically be freed
+ * when no longer needed.
+ *
+ * There is no API for deregistering a callback once registered.  If you
+ * want it to not do anything anymore, adjust the state pointed to by its
+ * "arg" to indicate that.
+ */
+void
+MemoryContextRegisterResetCallback(MemoryContext context,
+								   MemoryContextCallback *cb)
+{
+	AssertArg(MemoryContextIsValid(context));
+
+	/* Push onto head so this will be called before older registrants. */
+	cb->next = context->reset_cbs;
+	context->reset_cbs = cb;
+	/* Mark the context as non-reset (it probably is already). */
+	context->isReset = false;
+}
+
+/*
+ * MemoryContextCallResetCallbacks
+ *		Internal function to call all registered callbacks for context.
+ */
+static void
+MemoryContextCallResetCallbacks(MemoryContext context)
+{
+	MemoryContextCallback *cb;
+
+	/*
+	 * We pop each callback from the list before calling.  That way, if an
+	 * error occurs inside the callback, we won't try to call it a second time
+	 * in the likely event that we reset or delete the context later.
+	 */
+	while ((cb = context->reset_cbs) != NULL)
+	{
+		context->reset_cbs = cb->next;
+		cb->func(cb->arg);
+	}
+}
+
+/*
+ * MemoryContextSetIdentifier
+ *		Set the identifier string for a memory context.
+ *
+ * An identifier can be provided to help distinguish among different contexts
+ * of the same kind in memory context stats dumps.  The identifier string
+ * must live at least as long as the context it is for; typically it is
+ * allocated inside that context, so that it automatically goes away on
+ * context deletion.  Pass id = NULL to forget any old identifier.
+ */
+void
+MemoryContextSetIdentifier(MemoryContext context, const char *id)
+{
+	AssertArg(MemoryContextIsValid(context));
+	context->ident = id;
+}
+
+/*
+ * MemoryContextSetParent
+ *		Change a context to belong to a new parent (or no parent).
+ *
+ * We provide this as an API function because it is sometimes useful to
+ * change a context's lifespan after creation.  For example, a context
+ * might be created underneath a transient context, filled with data,
+ * and then reparented underneath CacheMemoryContext to make it long-lived.
+ * In this way no special effort is needed to get rid of the context in case
+ * a failure occurs before its contents are completely set up.
+ *
+ * Callers often assume that this function cannot fail, so don't put any
+ * elog(ERROR) calls in it.
+ *
+ * A possible caller error is to reparent a context under itself, creating
+ * a loop in the context graph.  We assert here that context != new_parent,
+ * but checking for multi-level loops seems more trouble than it's worth.
+ */
+void
+MemoryContextSetParent(MemoryContext context, MemoryContext new_parent)
+{
+	AssertArg(MemoryContextIsValid(context));
+	AssertArg(context != new_parent);
+
+	/* Fast path if it's got correct parent already */
+	if (new_parent == context->parent)
+		return;
+
+	/* Delink from existing parent, if any */
+	if (context->parent)
+	{
+		MemoryContext parent = context->parent;
+
+		if (context->prevchild != NULL)
+			context->prevchild->nextchild = context->nextchild;
+		else
+		{
+			Assert(parent->firstchild == context);
+			parent->firstchild = context->nextchild;
+		}
+
+		if (context->nextchild != NULL)
+			context->nextchild->prevchild = context->prevchild;
+	}
+
+	/* And relink */
+	if (new_parent)
+	{
+		AssertArg(MemoryContextIsValid(new_parent));
+		context->parent = new_parent;
+		context->prevchild = NULL;
+		context->nextchild = new_parent->firstchild;
+		if (new_parent->firstchild != NULL)
+			new_parent->firstchild->prevchild = context;
+		new_parent->firstchild = context;
+	}
+	else
+	{
+		context->parent = NULL;
+		context->prevchild = NULL;
+		context->nextchild = NULL;
+	}
+}
+
+/*
+ * MemoryContextAllowInCriticalSection
+ *		Allow/disallow allocations in this memory context within a critical
+ *		section.
+ *
+ * Normally, memory allocations are not allowed within a critical section,
+ * because a failure would lead to PANIC.  There are a few exceptions to
+ * that, like allocations related to debugging code that is not supposed to
+ * be enabled in production.  This function can be used to exempt specific
+ * memory contexts from the assertion in palloc().
+ */
+void
+MemoryContextAllowInCriticalSection(MemoryContext context, bool allow)
+{
+	AssertArg(MemoryContextIsValid(context));
+
+	context->allowInCritSection = allow;
+}
+
+/*
+ * GetMemoryChunkSpace
+ *		Given a currently-allocated chunk, determine the total space
+ *		it occupies (including all memory-allocation overhead).
+ *
+ * This is useful for measuring the total space occupied by a set of
+ * allocated chunks.
+ */
+Size
+GetMemoryChunkSpace(void *pointer)
+{
+	MemoryContext context = GetMemoryChunkContext(pointer);
+
+	return context->methods->get_chunk_space(context, pointer);
+}
+
+/*
+ * MemoryContextGetParent
+ *		Get the parent context (if any) of the specified context
+ */
+MemoryContext
+MemoryContextGetParent(MemoryContext context)
+{
+	AssertArg(MemoryContextIsValid(context));
+
+	return context->parent;
+}
+
+/*
+ * MemoryContextIsEmpty
+ *		Is a memory context empty of any allocated space?
+ */
+bool
+MemoryContextIsEmpty(MemoryContext context)
+{
+	AssertArg(MemoryContextIsValid(context));
+
+	/*
+	 * For now, we consider a memory context nonempty if it has any children;
+	 * perhaps this should be changed later.
+	 */
+	if (context->firstchild != NULL)
+		return false;
+	/* Otherwise use the type-specific inquiry */
+	return context->methods->is_empty(context);
+}
+
+/*
+ * Find the memory allocated to blocks for this memory context. If recurse is
+ * true, also include children.
+ */
+Size
+MemoryContextMemAllocated(MemoryContext context, bool recurse)
+{
+	Size		total = context->mem_allocated;
+
+	AssertArg(MemoryContextIsValid(context));
+
+	if (recurse)
+	{
+		MemoryContext child;
+
+		for (child = context->firstchild;
+			 child != NULL;
+			 child = child->nextchild)
+			total += MemoryContextMemAllocated(child, true);
+	}
+
+	return total;
+}
+
+/*
+ * MemoryContextStats
+ *		Print statistics about the named context and all its descendants.
+ *
+ * This is just a debugging utility, so it's not very fancy.  However, we do
+ * make some effort to summarize when the output would otherwise be very long.
+ * The statistics are sent to stderr.
+ */
+void
+MemoryContextStats(MemoryContext context)
+{
+	/* A hard-wired limit on the number of children is usually good enough */
+	MemoryContextStatsDetail(context, 100, true);
+}
+
+/*
+ * MemoryContextStatsDetail
+ *
+ * Entry point for use if you want to vary the number of child contexts shown.
+ *
+ * If print_to_stderr is true, print statistics about the memory contexts
+ * with fprintf(stderr), otherwise use ereport().
+ */
+void
+MemoryContextStatsDetail(MemoryContext context, int max_children,
+						 bool print_to_stderr)
+{
+	MemoryContextCounters grand_totals;
+
+	memset(&grand_totals, 0, sizeof(grand_totals));
+
+	MemoryContextStatsInternal(context, 0, true, max_children, &grand_totals, print_to_stderr);
+
+	if (print_to_stderr)
+		fprintf(stderr,
+				"Grand total: %zu bytes in %zd blocks; %zu free (%zd chunks); %zu used\n",
+				grand_totals.totalspace, grand_totals.nblocks,
+				grand_totals.freespace, grand_totals.freechunks,
+				grand_totals.totalspace - grand_totals.freespace);
+	else
+
+		/*
+		 * Use LOG_SERVER_ONLY to prevent the memory contexts from being sent
+		 * to the connected client.
+		 *
+		 * We don't buffer the information about all memory contexts in a
+		 * backend into StringInfo and log it as one message. Otherwise which
+		 * may require the buffer to be enlarged very much and lead to OOM
+		 * error since there can be a large number of memory contexts in a
+		 * backend. Instead, we log one message per memory context.
+		 */
+		ereport(LOG_SERVER_ONLY,
+				(errhidestmt(true),
+				 errhidecontext(true),
+				 errmsg_internal("Grand total: %zu bytes in %zd blocks; %zu free (%zd chunks); %zu used",
+								 grand_totals.totalspace, grand_totals.nblocks,
+								 grand_totals.freespace, grand_totals.freechunks,
+								 grand_totals.totalspace - grand_totals.freespace)));
+}
+
+/*
+ * MemoryContextStatsInternal
+ *		One recursion level for MemoryContextStats
+ *
+ * Print this context if print is true, but in any case accumulate counts into
+ * *totals (if given).
+ */
+static void
+MemoryContextStatsInternal(MemoryContext context, int level,
+						   bool print, int max_children,
+						   MemoryContextCounters *totals,
+						   bool print_to_stderr)
+{
+	MemoryContextCounters local_totals;
+	MemoryContext child;
+	int			ichild;
+
+	AssertArg(MemoryContextIsValid(context));
+
+	/* Examine the context itself */
+	context->methods->stats(context,
+							print ? MemoryContextStatsPrint : NULL,
+							(void *) &level,
+							totals, print_to_stderr);
+
+	/*
+	 * Examine children.  If there are more than max_children of them, we do
+	 * not print the rest explicitly, but just summarize them.
+	 */
+	memset(&local_totals, 0, sizeof(local_totals));
+
+	for (child = context->firstchild, ichild = 0;
+		 child != NULL;
+		 child = child->nextchild, ichild++)
+	{
+		if (ichild < max_children)
+			MemoryContextStatsInternal(child, level + 1,
+									   print, max_children,
+									   totals,
+									   print_to_stderr);
+		else
+			MemoryContextStatsInternal(child, level + 1,
+									   false, max_children,
+									   &local_totals,
+									   print_to_stderr);
+	}
+
+	/* Deal with excess children */
+	if (ichild > max_children)
+	{
+		if (print)
+		{
+			if (print_to_stderr)
+			{
+				int			i;
+
+				for (i = 0; i <= level; i++)
+					fprintf(stderr, "  ");
+				fprintf(stderr,
+						"%d more child contexts containing %zu total in %zd blocks; %zu free (%zd chunks); %zu used\n",
+						ichild - max_children,
+						local_totals.totalspace,
+						local_totals.nblocks,
+						local_totals.freespace,
+						local_totals.freechunks,
+						local_totals.totalspace - local_totals.freespace);
+			}
+			else
+				ereport(LOG_SERVER_ONLY,
+						(errhidestmt(true),
+						 errhidecontext(true),
+						 errmsg_internal("level: %d; %d more child contexts containing %zu total in %zd blocks; %zu free (%zd chunks); %zu used",
+										 level,
+										 ichild - max_children,
+										 local_totals.totalspace,
+										 local_totals.nblocks,
+										 local_totals.freespace,
+										 local_totals.freechunks,
+										 local_totals.totalspace - local_totals.freespace)));
+		}
+
+		if (totals)
+		{
+			totals->nblocks += local_totals.nblocks;
+			totals->freechunks += local_totals.freechunks;
+			totals->totalspace += local_totals.totalspace;
+			totals->freespace += local_totals.freespace;
+		}
+	}
+}
+
+/*
+ * MemoryContextStatsPrint
+ *		Print callback used by MemoryContextStatsInternal
+ *
+ * For now, the passthru pointer just points to "int level"; later we might
+ * make that more complicated.
+ */
+static void
+MemoryContextStatsPrint(MemoryContext context, void *passthru,
+						const char *stats_string,
+						bool print_to_stderr)
+{
+	int			level = *(int *) passthru;
+	const char *name = context->name;
+	const char *ident = context->ident;
+	char		truncated_ident[110];
+	int			i;
+
+	/*
+	 * It seems preferable to label dynahash contexts with just the hash table
+	 * name.  Those are already unique enough, so the "dynahash" part isn't
+	 * very helpful, and this way is more consistent with pre-v11 practice.
+	 */
+	if (ident && strcmp(name, "dynahash") == 0)
+	{
+		name = ident;
+		ident = NULL;
+	}
+
+	truncated_ident[0] = '\0';
+
+	if (ident)
+	{
+		/*
+		 * Some contexts may have very long identifiers (e.g., SQL queries).
+		 * Arbitrarily truncate at 100 bytes, but be careful not to break
+		 * multibyte characters.  Also, replace ASCII control characters, such
+		 * as newlines, with spaces.
+		 */
+		int			idlen = strlen(ident);
+		bool		truncated = false;
+
+		strcpy(truncated_ident, ": ");
+		i = strlen(truncated_ident);
+
+		if (idlen > 100)
+		{
+			idlen = pg_mbcliplen(ident, idlen, 100);
+			truncated = true;
+		}
+
+		while (idlen-- > 0)
+		{
+			unsigned char c = *ident++;
+
+			if (c < ' ')
+				c = ' ';
+			truncated_ident[i++] = c;
+		}
+		truncated_ident[i] = '\0';
+
+		if (truncated)
+			strcat(truncated_ident, "...");
+	}
+
+	if (print_to_stderr)
+	{
+		for (i = 0; i < level; i++)
+			fprintf(stderr, "  ");
+		fprintf(stderr, "%s: %s%s\n", name, stats_string, truncated_ident);
+	}
+	else
+		ereport(LOG_SERVER_ONLY,
+				(errhidestmt(true),
+				 errhidecontext(true),
+				 errmsg_internal("level: %d; %s: %s%s",
+								 level, name, stats_string, truncated_ident)));
+}
+
+/*
+ * MemoryContextCheck
+ *		Check all chunks in the named context.
+ *
+ * This is just a debugging utility, so it's not fancy.
+ */
+#ifdef MEMORY_CONTEXT_CHECKING
+void
+MemoryContextCheck(MemoryContext context)
+{
+	MemoryContext child;
+
+	AssertArg(MemoryContextIsValid(context));
+
+	context->methods->check(context);
+	for (child = context->firstchild; child != NULL; child = child->nextchild)
+		MemoryContextCheck(child);
+}
+#endif
+
+/*
+ * MemoryContextContains
+ *		Detect whether an allocated chunk of memory belongs to a given
+ *		context or not.
+ *
+ * Caution: this test is reliable as long as 'pointer' does point to
+ * a chunk of memory allocated from *some* context.  If 'pointer' points
+ * at memory obtained in some other way, there is a small chance of a
+ * false-positive result, since the bits right before it might look like
+ * a valid chunk header by chance.
+ */
+bool
+MemoryContextContains(MemoryContext context, void *pointer)
+{
+	MemoryContext ptr_context;
+
+	/*
+	 * NB: Can't use GetMemoryChunkContext() here - that performs assertions
+	 * that aren't acceptable here since we might be passed memory not
+	 * allocated by any memory context.
+	 *
+	 * Try to detect bogus pointers handed to us, poorly though we can.
+	 * Presumably, a pointer that isn't MAXALIGNED isn't pointing at an
+	 * allocated chunk.
+	 */
+	if (pointer == NULL || pointer != (void *) MAXALIGN(pointer))
+		return false;
+
+	/*
+	 * OK, it's probably safe to look at the context.
+	 */
+	ptr_context = *(MemoryContext *) (((char *) pointer) - sizeof(void *));
+
+	return ptr_context == context;
+}
+
+/*
+ * MemoryContextCreate
+ *		Context-type-independent part of context creation.
+ *
+ * This is only intended to be called by context-type-specific
+ * context creation routines, not by the unwashed masses.
+ *
+ * The memory context creation procedure goes like this:
+ *	1.  Context-type-specific routine makes some initial space allocation,
+ *		including enough space for the context header.  If it fails,
+ *		it can ereport() with no damage done.
+ *	2.	Context-type-specific routine sets up all type-specific fields of
+ *		the header (those beyond MemoryContextData proper), as well as any
+ *		other management fields it needs to have a fully valid context.
+ *		Usually, failure in this step is impossible, but if it's possible
+ *		the initial space allocation should be freed before ereport'ing.
+ *	3.	Context-type-specific routine calls MemoryContextCreate() to fill in
+ *		the generic header fields and link the context into the context tree.
+ *	4.  We return to the context-type-specific routine, which finishes
+ *		up type-specific initialization.  This routine can now do things
+ *		that might fail (like allocate more memory), so long as it's
+ *		sure the node is left in a state that delete will handle.
+ *
+ * node: the as-yet-uninitialized common part of the context header node.
+ * tag: NodeTag code identifying the memory context type.
+ * methods: context-type-specific methods (usually statically allocated).
+ * parent: parent context, or NULL if this will be a top-level context.
+ * name: name of context (must be statically allocated).
+ *
+ * Context routines generally assume that MemoryContextCreate can't fail,
+ * so this can contain Assert but not elog/ereport.
+ */
+void
+MemoryContextCreate(MemoryContext node,
+					NodeTag tag,
+					const MemoryContextMethods *methods,
+					MemoryContext parent,
+					const char *name)
+{
+	/* Creating new memory contexts is not allowed in a critical section */
+	Assert(CritSectionCount == 0);
+
+	/* Initialize all standard fields of memory context header */
+	node->type = tag;
+	node->isReset = true;
+	node->methods = methods;
+	node->parent = parent;
+	node->firstchild = NULL;
+	node->mem_allocated = 0;
+	node->prevchild = NULL;
+	node->name = name;
+	node->ident = NULL;
+	node->reset_cbs = NULL;
+
+	/* OK to link node into context tree */
+	if (parent)
+	{
+		node->nextchild = parent->firstchild;
+		if (parent->firstchild != NULL)
+			parent->firstchild->prevchild = node;
+		parent->firstchild = node;
+		/* inherit allowInCritSection flag from parent */
+		node->allowInCritSection = parent->allowInCritSection;
+	}
+	else
+	{
+		node->nextchild = NULL;
+		node->allowInCritSection = false;
+	}
+
+	VALGRIND_CREATE_MEMPOOL(node, 0, false);
+}
+
+/*
+ * MemoryContextAlloc
+ *		Allocate space within the specified context.
+ *
+ * This could be turned into a macro, but we'd have to import
+ * nodes/memnodes.h into postgres.h which seems a bad idea.
+ */
+void *
+MemoryContextAlloc(MemoryContext context, Size size)
+{
+	void	   *ret;
+
+	AssertArg(MemoryContextIsValid(context));
+	AssertNotInCriticalSection(context);
+
+	if (!AllocSizeIsValid(size))
+		elog(ERROR, "invalid memory alloc request size %zu", size);
+
+	context->isReset = false;
+
+	ret = context->methods->alloc(context, size);
+	if (unlikely(ret == NULL))
+	{
+		MemoryContextStats(TopMemoryContext);
+
+		/*
+		 * Here, and elsewhere in this module, we show the target context's
+		 * "name" but not its "ident" (if any) in user-visible error messages.
+		 * The "ident" string might contain security-sensitive data, such as
+		 * values in SQL commands.
+		 */
+		ereport(ERROR,
+				(errcode(ERRCODE_OUT_OF_MEMORY),
+				 errmsg("out of memory"),
+				 errdetail("Failed on request of size %zu in memory context \"%s\".",
+						   size, context->name)));
+	}
+
+	VALGRIND_MEMPOOL_ALLOC(context, ret, size);
+
+	return ret;
+}
+
+/*
+ * MemoryContextAllocZero
+ *		Like MemoryContextAlloc, but clears allocated memory
+ *
+ *	We could just call MemoryContextAlloc then clear the memory, but this
+ *	is a very common combination, so we provide the combined operation.
+ */
+void *
+MemoryContextAllocZero(MemoryContext context, Size size)
+{
+	void	   *ret;
+
+	AssertArg(MemoryContextIsValid(context));
+	AssertNotInCriticalSection(context);
+
+	if (!AllocSizeIsValid(size))
+		elog(ERROR, "invalid memory alloc request size %zu", size);
+
+	context->isReset = false;
+
+	ret = context->methods->alloc(context, size);
+	if (unlikely(ret == NULL))
+	{
+		MemoryContextStats(TopMemoryContext);
+		ereport(ERROR,
+				(errcode(ERRCODE_OUT_OF_MEMORY),
+				 errmsg("out of memory"),
+				 errdetail("Failed on request of size %zu in memory context \"%s\".",
+						   size, context->name)));
+	}
+
+	VALGRIND_MEMPOOL_ALLOC(context, ret, size);
+
+	MemSetAligned(ret, 0, size);
+
+	return ret;
+}
+
+/*
+ * MemoryContextAllocZeroAligned
+ *		MemoryContextAllocZero where length is suitable for MemSetLoop
+ *
+ *	This might seem overly specialized, but it's not because newNode()
+ *	is so often called with compile-time-constant sizes.
+ */
+void *
+MemoryContextAllocZeroAligned(MemoryContext context, Size size)
+{
+	void	   *ret;
+
+	AssertArg(MemoryContextIsValid(context));
+	AssertNotInCriticalSection(context);
+
+	if (!AllocSizeIsValid(size))
+		elog(ERROR, "invalid memory alloc request size %zu", size);
+
+	context->isReset = false;
+
+	ret = context->methods->alloc(context, size);
+	if (unlikely(ret == NULL))
+	{
+		MemoryContextStats(TopMemoryContext);
+		ereport(ERROR,
+				(errcode(ERRCODE_OUT_OF_MEMORY),
+				 errmsg("out of memory"),
+				 errdetail("Failed on request of size %zu in memory context \"%s\".",
+						   size, context->name)));
+	}
+
+	VALGRIND_MEMPOOL_ALLOC(context, ret, size);
+
+	MemSetLoop(ret, 0, size);
+
+	return ret;
+}
+
+/*
+ * MemoryContextAllocExtended
+ *		Allocate space within the specified context using the given flags.
+ */
+void *
+MemoryContextAllocExtended(MemoryContext context, Size size, int flags)
+{
+	void	   *ret;
+
+	AssertArg(MemoryContextIsValid(context));
+	AssertNotInCriticalSection(context);
+
+	if (((flags & MCXT_ALLOC_HUGE) != 0 && !AllocHugeSizeIsValid(size)) ||
+		((flags & MCXT_ALLOC_HUGE) == 0 && !AllocSizeIsValid(size)))
+		elog(ERROR, "invalid memory alloc request size %zu", size);
+
+	context->isReset = false;
+
+	ret = context->methods->alloc(context, size);
+	if (unlikely(ret == NULL))
+	{
+		if ((flags & MCXT_ALLOC_NO_OOM) == 0)
+		{
+			MemoryContextStats(TopMemoryContext);
+			ereport(ERROR,
+					(errcode(ERRCODE_OUT_OF_MEMORY),
+					 errmsg("out of memory"),
+					 errdetail("Failed on request of size %zu in memory context \"%s\".",
+							   size, context->name)));
+		}
+		return NULL;
+	}
+
+	VALGRIND_MEMPOOL_ALLOC(context, ret, size);
+
+	if ((flags & MCXT_ALLOC_ZERO) != 0)
+		MemSetAligned(ret, 0, size);
+
+	return ret;
+}
+
+/*
+ * HandleLogMemoryContextInterrupt
+ *		Handle receipt of an interrupt indicating logging of memory
+ *		contexts.
+ *
+ * All the actual work is deferred to ProcessLogMemoryContextInterrupt(),
+ * because we cannot safely emit a log message inside the signal handler.
+ */
+void
+HandleLogMemoryContextInterrupt(void)
+{
+	InterruptPending = true;
+	LogMemoryContextPending = true;
+	/* latch will be set by procsignal_sigusr1_handler */
+}
+
+/*
+ * ProcessLogMemoryContextInterrupt
+ * 		Perform logging of memory contexts of this backend process.
+ *
+ * Any backend that participates in ProcSignal signaling must arrange
+ * to call this function if we see LogMemoryContextPending set.
+ * It is called from CHECK_FOR_INTERRUPTS(), which is enough because
+ * the target process for logging of memory contexts is a backend.
+ */
+void
+ProcessLogMemoryContextInterrupt(void)
+{
+	LogMemoryContextPending = false;
+
+	/*
+	 * Use LOG_SERVER_ONLY to prevent this message from being sent to the
+	 * connected client.
+	 */
+	ereport(LOG_SERVER_ONLY,
+			(errhidestmt(true),
+			 errhidecontext(true),
+			 errmsg("logging memory contexts of PID %d", MyProcPid)));
+
+	/*
+	 * When a backend process is consuming huge memory, logging all its memory
+	 * contexts might overrun available disk space. To prevent this, we limit
+	 * the number of child contexts to log per parent to 100.
+	 *
+	 * As with MemoryContextStats(), we suppose that practical cases where the
+	 * dump gets long will typically be huge numbers of siblings under the
+	 * same parent context; while the additional debugging value from seeing
+	 * details about individual siblings beyond 100 will not be large.
+	 */
+	MemoryContextStatsDetail(TopMemoryContext, 100, false);
+}
+
+void *
+palloc(Size size)
+{
+	/* duplicates MemoryContextAlloc to avoid increased overhead */
+	void	   *ret;
+	MemoryContext context = CurrentMemoryContext;
+
+	AssertArg(MemoryContextIsValid(context));
+	AssertNotInCriticalSection(context);
+
+	if (!AllocSizeIsValid(size))
+		elog(ERROR, "invalid memory alloc request size %zu", size);
+
+	context->isReset = false;
+
+	ret = context->methods->alloc(context, size);
+	if (unlikely(ret == NULL))
+	{
+		MemoryContextStats(TopMemoryContext);
+		ereport(ERROR,
+				(errcode(ERRCODE_OUT_OF_MEMORY),
+				 errmsg("out of memory"),
+				 errdetail("Failed on request of size %zu in memory context \"%s\".",
+						   size, context->name)));
+	}
+
+	VALGRIND_MEMPOOL_ALLOC(context, ret, size);
+
+	return ret;
+}
+
+void *
+palloc0(Size size)
+{
+	/* duplicates MemoryContextAllocZero to avoid increased overhead */
+	void	   *ret;
+	MemoryContext context = CurrentMemoryContext;
+
+	AssertArg(MemoryContextIsValid(context));
+	AssertNotInCriticalSection(context);
+
+	if (!AllocSizeIsValid(size))
+		elog(ERROR, "invalid memory alloc request size %zu", size);
+
+	context->isReset = false;
+
+	ret = context->methods->alloc(context, size);
+	if (unlikely(ret == NULL))
+	{
+		MemoryContextStats(TopMemoryContext);
+		ereport(ERROR,
+				(errcode(ERRCODE_OUT_OF_MEMORY),
+				 errmsg("out of memory"),
+				 errdetail("Failed on request of size %zu in memory context \"%s\".",
+						   size, context->name)));
+	}
+
+	VALGRIND_MEMPOOL_ALLOC(context, ret, size);
+
+	MemSetAligned(ret, 0, size);
+
+	return ret;
+}
+
+void *
+palloc_extended(Size size, int flags)
+{
+	/* duplicates MemoryContextAllocExtended to avoid increased overhead */
+	void	   *ret;
+	MemoryContext context = CurrentMemoryContext;
+
+	AssertArg(MemoryContextIsValid(context));
+	AssertNotInCriticalSection(context);
+
+	if (((flags & MCXT_ALLOC_HUGE) != 0 && !AllocHugeSizeIsValid(size)) ||
+		((flags & MCXT_ALLOC_HUGE) == 0 && !AllocSizeIsValid(size)))
+		elog(ERROR, "invalid memory alloc request size %zu", size);
+
+	context->isReset = false;
+
+	ret = context->methods->alloc(context, size);
+	if (unlikely(ret == NULL))
+	{
+		if ((flags & MCXT_ALLOC_NO_OOM) == 0)
+		{
+			MemoryContextStats(TopMemoryContext);
+			ereport(ERROR,
+					(errcode(ERRCODE_OUT_OF_MEMORY),
+					 errmsg("out of memory"),
+					 errdetail("Failed on request of size %zu in memory context \"%s\".",
+							   size, context->name)));
+		}
+		return NULL;
+	}
+
+	VALGRIND_MEMPOOL_ALLOC(context, ret, size);
+
+	if ((flags & MCXT_ALLOC_ZERO) != 0)
+		MemSetAligned(ret, 0, size);
+
+	return ret;
+}
+
+/*
+ * pfree
+ *		Release an allocated chunk.
+ */
+void
+pfree(void *pointer)
+{
+	MemoryContext context = GetMemoryChunkContext(pointer);
+
+	context->methods->free_p(context, pointer);
+	VALGRIND_MEMPOOL_FREE(context, pointer);
+}
+
+/*
+ * repalloc
+ *		Adjust the size of a previously allocated chunk.
+ */
+void *
+repalloc(void *pointer, Size size)
+{
+	MemoryContext context = GetMemoryChunkContext(pointer);
+	void	   *ret;
+
+	if (!AllocSizeIsValid(size))
+		elog(ERROR, "invalid memory alloc request size %zu", size);
+
+	AssertNotInCriticalSection(context);
+
+	/* isReset must be false already */
+	Assert(!context->isReset);
+
+	ret = context->methods->realloc(context, pointer, size);
+	if (unlikely(ret == NULL))
+	{
+		MemoryContextStats(TopMemoryContext);
+		ereport(ERROR,
+				(errcode(ERRCODE_OUT_OF_MEMORY),
+				 errmsg("out of memory"),
+				 errdetail("Failed on request of size %zu in memory context \"%s\".",
+						   size, context->name)));
+	}
+
+	VALGRIND_MEMPOOL_CHANGE(context, pointer, ret, size);
+
+	return ret;
+}
+
+/*
+ * MemoryContextAllocHuge
+ *		Allocate (possibly-expansive) space within the specified context.
+ *
+ * See considerations in comment at MaxAllocHugeSize.
+ */
+void *
+MemoryContextAllocHuge(MemoryContext context, Size size)
+{
+	void	   *ret;
+
+	AssertArg(MemoryContextIsValid(context));
+	AssertNotInCriticalSection(context);
+
+	if (!AllocHugeSizeIsValid(size))
+		elog(ERROR, "invalid memory alloc request size %zu", size);
+
+	context->isReset = false;
+
+	ret = context->methods->alloc(context, size);
+	if (unlikely(ret == NULL))
+	{
+		MemoryContextStats(TopMemoryContext);
+		ereport(ERROR,
+				(errcode(ERRCODE_OUT_OF_MEMORY),
+				 errmsg("out of memory"),
+				 errdetail("Failed on request of size %zu in memory context \"%s\".",
+						   size, context->name)));
+	}
+
+	VALGRIND_MEMPOOL_ALLOC(context, ret, size);
+
+	return ret;
+}
+
+/*
+ * repalloc_huge
+ *		Adjust the size of a previously allocated chunk, permitting a large
+ *		value.  The previous allocation need not have been "huge".
+ */
+void *
+repalloc_huge(void *pointer, Size size)
+{
+	MemoryContext context = GetMemoryChunkContext(pointer);
+	void	   *ret;
+
+	if (!AllocHugeSizeIsValid(size))
+		elog(ERROR, "invalid memory alloc request size %zu", size);
+
+	AssertNotInCriticalSection(context);
+
+	/* isReset must be false already */
+	Assert(!context->isReset);
+
+	ret = context->methods->realloc(context, pointer, size);
+	if (unlikely(ret == NULL))
+	{
+		MemoryContextStats(TopMemoryContext);
+		ereport(ERROR,
+				(errcode(ERRCODE_OUT_OF_MEMORY),
+				 errmsg("out of memory"),
+				 errdetail("Failed on request of size %zu in memory context \"%s\".",
+						   size, context->name)));
+	}
+
+	VALGRIND_MEMPOOL_CHANGE(context, pointer, ret, size);
+
+	return ret;
+}
+
+/*
+ * MemoryContextStrdup
+ *		Like strdup(), but allocate from the specified context
+ */
+char *
+MemoryContextStrdup(MemoryContext context, const char *string)
+{
+	char	   *nstr;
+	Size		len = strlen(string) + 1;
+
+	nstr = (char *) MemoryContextAlloc(context, len);
+
+	memcpy(nstr, string, len);
+
+	return nstr;
+}
+
+char *
+pstrdup(const char *in)
+{
+	return MemoryContextStrdup(CurrentMemoryContext, in);
+}
+
+/*
+ * pnstrdup
+ *		Like pstrdup(), but append null byte to a
+ *		not-necessarily-null-terminated input string.
+ */
+char *
+pnstrdup(const char *in, Size len)
+{
+	char	   *out;
+
+	len = strnlen(in, len);
+
+	out = palloc(len + 1);
+	memcpy(out, in, len);
+	out[len] = '\0';
+
+	return out;
+}
+
+/*
+ * Make copy of string with all trailing newline characters removed.
+ */
+char *
+pchomp(const char *in)
+{
+	size_t		n;
+
+	n = strlen(in);
+	while (n > 0 && in[n - 1] == '\n')
+		n--;
+	return pnstrdup(in, n);
+}