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diff --git a/src/include/common/kwlookup.h b/src/include/common/kwlookup.h
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+++ b/src/include/common/kwlookup.h
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+/*-------------------------------------------------------------------------
+ *
+ * kwlookup.h
+ *	  Key word lookup for PostgreSQL
+ *
+ *
+ * Portions Copyright (c) 1996-2020, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/include/common/kwlookup.h
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef KWLOOKUP_H
+#define KWLOOKUP_H
+
+/* Hash function used by ScanKeywordLookup */
+typedef int (*ScanKeywordHashFunc) (const void *key, size_t keylen);
+
+/*
+ * This struct contains the data needed by ScanKeywordLookup to perform a
+ * search within a set of keywords.  The contents are typically generated by
+ * src/tools/gen_keywordlist.pl from a header containing PG_KEYWORD macros.
+ */
+typedef struct ScanKeywordList
+{
+	const char *kw_string;		/* all keywords in order, separated by \0 */
+	const uint16 *kw_offsets;	/* offsets to the start of each keyword */
+	ScanKeywordHashFunc hash;	/* perfect hash function for keywords */
+	int			num_keywords;	/* number of keywords */
+	int			max_kw_len;		/* length of longest keyword */
+} ScanKeywordList;
+
+
+extern int	ScanKeywordLookup(const char *text, const ScanKeywordList *keywords);
+
+/* Code that wants to retrieve the text of the N'th keyword should use this. */
+static inline const char *
+GetScanKeyword(int n, const ScanKeywordList *keywords)
+{
+	return keywords->kw_string + keywords->kw_offsets[n];
+}
+
+#endif							/* KWLOOKUP_H */