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diff --git a/src/include/lib/pairingheap.h b/src/include/lib/pairingheap.h
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+++ b/src/include/lib/pairingheap.h
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+/*
+ * pairingheap.h
+ *
+ * A Pairing Heap implementation
+ *
+ * Portions Copyright (c) 2012-2020, PostgreSQL Global Development Group
+ *
+ * src/include/lib/pairingheap.h
+ */
+
+#ifndef PAIRINGHEAP_H
+#define PAIRINGHEAP_H
+
+#include "lib/stringinfo.h"
+
+/* Enable if you need the pairingheap_dump() debug function */
+/* #define PAIRINGHEAP_DEBUG */
+
+/*
+ * This represents an element stored in the heap. Embed this in a larger
+ * struct containing the actual data you're storing.
+ *
+ * A node can have multiple children, which form a double-linked list.
+ * first_child points to the node's first child, and the subsequent children
+ * can be found by following the next_sibling pointers. The last child has
+ * next_sibling == NULL. The prev_or_parent pointer points to the node's
+ * previous sibling, or if the node is its parent's first child, to the
+ * parent.
+ */
+typedef struct pairingheap_node
+{
+	struct pairingheap_node *first_child;
+	struct pairingheap_node *next_sibling;
+	struct pairingheap_node *prev_or_parent;
+} pairingheap_node;
+
+/*
+ * Return the containing struct of 'type' where 'membername' is the
+ * pairingheap_node pointed at by 'ptr'.
+ *
+ * This is used to convert a pairingheap_node * back to its containing struct.
+ */
+#define pairingheap_container(type, membername, ptr) \
+	(AssertVariableIsOfTypeMacro(ptr, pairingheap_node *), \
+	 AssertVariableIsOfTypeMacro(((type *) NULL)->membername, pairingheap_node),  \
+	 ((type *) ((char *) (ptr) - offsetof(type, membername))))
+
+/*
+ * Like pairingheap_container, but used when the pointer is 'const ptr'
+ */
+#define pairingheap_const_container(type, membername, ptr) \
+	(AssertVariableIsOfTypeMacro(ptr, const pairingheap_node *), \
+	 AssertVariableIsOfTypeMacro(((type *) NULL)->membername, pairingheap_node),  \
+	 ((const type *) ((const char *) (ptr) - offsetof(type, membername))))
+
+/*
+ * For a max-heap, the comparator must return <0 iff a < b, 0 iff a == b,
+ * and >0 iff a > b.  For a min-heap, the conditions are reversed.
+ */
+typedef int (*pairingheap_comparator) (const pairingheap_node *a,
+									   const pairingheap_node *b,
+									   void *arg);
+
+/*
+ * A pairing heap.
+ *
+ * You can use pairingheap_allocate() to create a new palloc'd heap, or embed
+ * this in a larger struct, set ph_compare and ph_arg directly and initialize
+ * ph_root to NULL.
+ */
+typedef struct pairingheap
+{
+	pairingheap_comparator ph_compare;	/* comparison function */
+	void	   *ph_arg;			/* opaque argument to ph_compare */
+	pairingheap_node *ph_root;	/* current root of the heap */
+} pairingheap;
+
+extern pairingheap *pairingheap_allocate(pairingheap_comparator compare,
+										 void *arg);
+extern void pairingheap_free(pairingheap *heap);
+extern void pairingheap_add(pairingheap *heap, pairingheap_node *node);
+extern pairingheap_node *pairingheap_first(pairingheap *heap);
+extern pairingheap_node *pairingheap_remove_first(pairingheap *heap);
+extern void pairingheap_remove(pairingheap *heap, pairingheap_node *node);
+
+#ifdef PAIRINGHEAP_DEBUG
+extern char *pairingheap_dump(pairingheap *heap,
+							  void (*dumpfunc) (pairingheap_node *node, StringInfo buf, void *opaque),
+							  void *opaque);
+#endif
+
+/* Resets the heap to be empty. */
+#define pairingheap_reset(h)			((h)->ph_root = NULL)
+
+/* Is the heap empty? */
+#define pairingheap_is_empty(h)			((h)->ph_root == NULL)
+
+/* Is there exactly one node in the heap? */
+#define pairingheap_is_singular(h) \
+	((h)->ph_root && (h)->ph_root->first_child == NULL)
+
+#endif							/* PAIRINGHEAP_H */