Add support for Daitch-Mokotoff Soundex in contrib/fuzzystrmatch.

This modernized version of Soundex works significantly better than
the original, particularly for non-English names.

Dag Lem, reviewed by quite a few people along the way

Discussion: https://postgr.es/m/yger1atbgfy.fsf@sid.nimrod.no

contrib/fuzzystrmatch/.gitignore

@@ -1,3 +1,5 @@
+# Generated files
+/daitch_mokotoff.h
 # Generated subdirectories
 /log/
 /results/

contrib/fuzzystrmatch/Makefile

@@ -3,14 +3,17 @@
 MODULE_big = fuzzystrmatch
 OBJS = \
 	$(WIN32RES) \
+	daitch_mokotoff.o \
 	dmetaphone.o \
 	fuzzystrmatch.o
 
 EXTENSION = fuzzystrmatch
-DATA = fuzzystrmatch--1.1.sql fuzzystrmatch--1.0--1.1.sql
+DATA = fuzzystrmatch--1.1.sql fuzzystrmatch--1.1--1.2.sql \
+	fuzzystrmatch--1.0--1.1.sql
+
 PGFILEDESC = "fuzzystrmatch - similarities and distance between strings"
 
-REGRESS = fuzzystrmatch
+REGRESS = fuzzystrmatch fuzzystrmatch_utf8
 
 ifdef USE_PGXS
 PG_CONFIG = pg_config
@@ -22,3 +25,16 @@ top_builddir = ../..
 include $(top_builddir)/src/Makefile.global
 include $(top_srcdir)/contrib/contrib-global.mk
 endif
+
+# Force this dependency to be known even without dependency info built:
+daitch_mokotoff.o: daitch_mokotoff.h
+
+daitch_mokotoff.h: daitch_mokotoff_header.pl
+	$(PERL) $< $@
+
+# daitch_mokotoff.h is included in tarballs, so it has to be made by
+# "distprep" and not cleaned except by "maintainer-clean".
+distprep: daitch_mokotoff.h
+
+maintainer-clean:
+	rm -f daitch_mokotoff.h

contrib/fuzzystrmatch/daitch_mokotoff.c

@@ -0,0 +1,577 @@
+/*
+ * Daitch-Mokotoff Soundex
+ *
+ * Copyright (c) 2023, PostgreSQL Global Development Group
+ *
+ * This module was originally sponsored by Finance Norway /
+ * Trafikkforsikringsforeningen, and implemented by Dag Lem <dag@nimrod.no>
+ *
+ * The implementation of the Daitch-Mokotoff Soundex System aims at correctness
+ * and high performance, and can be summarized as follows:
+ *
+ * - The processing of each phoneme is initiated by an O(1) table lookup.
+ * - For phonemes containing more than one character, a coding tree is traversed
+ *   to process the complete phoneme.
+ * - The (alternate) soundex codes are produced digit by digit in-place in
+ *   another tree structure.
+ *
+ * References:
+ *
+ * https://www.avotaynu.com/soundex.htm
+ * https://www.jewishgen.org/InfoFiles/Soundex.html
+ * https://familypedia.fandom.com/wiki/Daitch-Mokotoff_Soundex
+ * https://stevemorse.org/census/soundex.html (dmlat.php, dmsoundex.php)
+ * https://github.com/apache/commons-codec/ (dmrules.txt, DaitchMokotoffSoundex.java)
+ * https://metacpan.org/pod/Text::Phonetic (DaitchMokotoff.pm)
+ *
+ * A few notes on other implementations:
+ *
+ * - All other known implementations have the same unofficial rules for "UE",
+ *   these are also adapted by this implementation (0, 1, NC).
+ * - The only other known implementation which is capable of generating all
+ *   correct soundex codes in all cases is the JOS Soundex Calculator at
+ *   https://www.jewishgen.org/jos/jossound.htm
+ * - "J" is considered (only) a vowel in dmlat.php
+ * - The official rules for "RS" are commented out in dmlat.php
+ * - Identical code digits for adjacent letters are not collapsed correctly in
+ *   dmsoundex.php when double digit codes are involved. E.g. "BESST" yields
+ *   744300 instead of 743000 as for "BEST".
+ * - "J" is considered (only) a consonant in DaitchMokotoffSoundex.java
+ * - "Y" is not considered a vowel in DaitchMokotoffSoundex.java
+*/
+
+#include "postgres.h"
+
+#include "catalog/pg_type.h"
+#include "mb/pg_wchar.h"
+#include "utils/array.h"
+#include "utils/builtins.h"
+#include "utils/memutils.h"
+
+
+/*
+ * The soundex coding chart table is adapted from
+ * https://www.jewishgen.org/InfoFiles/Soundex.html
+ * See daitch_mokotoff_header.pl for details.
+*/
+
+/* Generated coding chart table */
+#include "daitch_mokotoff.h"
+
+#define DM_CODE_DIGITS 6
+
+/* Node in soundex code tree */
+typedef struct dm_node
+{
+	int			soundex_length; /* Length of generated soundex code */
+	char		soundex[DM_CODE_DIGITS];	/* Soundex code */
+	int			is_leaf;		/* Candidate for complete soundex code */
+	int			last_update;	/* Letter number for last update of node */
+	char		code_digit;		/* Last code digit, 0 - 9 */
+
+	/*
+	 * One or two alternate code digits leading to this node. If there are two
+	 * digits, one of them is always an 'X'. Repeated code digits and 'X' lead
+	 * back to the same node.
+	 */
+	char		prev_code_digits[2];
+	/* One or two alternate code digits moving forward. */
+	char		next_code_digits[2];
+	/* ORed together code index(es) used to reach current node. */
+	int			prev_code_index;
+	int			next_code_index;
+	/* Possible nodes branching out from this node - digits 0-9. */
+	struct dm_node *children[10];
+	/* Next node in linked list. Alternating index for each iteration. */
+	struct dm_node *next[2];
+} dm_node;
+
+/* Template for new node in soundex code tree. */
+static const dm_node start_node = {
+	.soundex_length = 0,
+	.soundex = "000000",		/* Six digits */
+	.is_leaf = 0,
+	.last_update = 0,
+	.code_digit = '\0',
+	.prev_code_digits = {'\0', '\0'},
+	.next_code_digits = {'\0', '\0'},
+	.prev_code_index = 0,
+	.next_code_index = 0,
+	.children = {NULL},
+	.next = {NULL}
+};
+
+/* Dummy soundex codes at end of input. */
+static const dm_codes end_codes[2] =
+{
+	{
+		"X", "X", "X"
+	}
+};
+
+/* Mapping from ISO8859-1 to upper-case ASCII, covering the range 0x60..0xFF. */
+static const char iso8859_1_to_ascii_upper[] =
+/*
+"`abcdefghijklmnopqrstuvwxyz{|}~                                  ¡¢£¤¥¦§¨©ª«¬ ®¯°±²³´µ¶·¸¹º»¼½¾¿ÀÁÂÃÄÅÆÇÈÉÊËÌÍÎÏÐÑÒÓÔÕÖ×ØÙÚÛÜÝÞßàáâãäåæçèéêëìíîïðñòóôõö÷øùúûüýþÿ"
+*/
+"`ABCDEFGHIJKLMNOPQRSTUVWXYZ{|}~                                  !                             ?AAAAAAECEEEEIIIIDNOOOOO*OUUUUYDSAAAAAAECEEEEIIIIDNOOOOO/OUUUUYDY";
+
+/* Internal C implementation */
+static bool daitch_mokotoff_coding(const char *word, ArrayBuildState *soundex);
+
+
+PG_FUNCTION_INFO_V1(daitch_mokotoff);
+
+Datum
+daitch_mokotoff(PG_FUNCTION_ARGS)
+{
+	text	   *arg = PG_GETARG_TEXT_PP(0);
+	Datum		retval;
+	char	   *string;
+	ArrayBuildState *soundex;
+	MemoryContext old_ctx,
+				tmp_ctx;
+
+	/* Work in a temporary context to simplify cleanup. */
+	tmp_ctx = AllocSetContextCreate(CurrentMemoryContext,
+									"daitch_mokotoff temporary context",
+									ALLOCSET_DEFAULT_SIZES);
+	old_ctx = MemoryContextSwitchTo(tmp_ctx);
+
+	/* We must convert the string to UTF-8 if it isn't already. */
+	string = pg_server_to_any(text_to_cstring(arg), VARSIZE_ANY_EXHDR(arg),
+							  PG_UTF8);
+
+	/* The result is built in this ArrayBuildState. */
+	soundex = initArrayResult(TEXTOID, tmp_ctx, false);
+
+	if (!daitch_mokotoff_coding(string, soundex))
+	{
+		/* No encodable characters in input */
+		MemoryContextSwitchTo(old_ctx);
+		MemoryContextDelete(tmp_ctx);
+		PG_RETURN_NULL();
+	}
+
+	retval = makeArrayResult(soundex, old_ctx);
+
+	MemoryContextSwitchTo(old_ctx);
+	MemoryContextDelete(tmp_ctx);
+
+	PG_RETURN_DATUM(retval);
+}
+
+
+/* Initialize soundex code tree node for next code digit. */
+static void
+initialize_node(dm_node *node, int last_update)
+{
+	if (node->last_update < last_update)
+	{
+		node->prev_code_digits[0] = node->next_code_digits[0];
+		node->prev_code_digits[1] = node->next_code_digits[1];
+		node->next_code_digits[0] = '\0';
+		node->next_code_digits[1] = '\0';
+		node->prev_code_index = node->next_code_index;
+		node->next_code_index = 0;
+		node->is_leaf = 0;
+		node->last_update = last_update;
+	}
+}
+
+
+/* Update soundex code tree node with next code digit. */
+static void
+add_next_code_digit(dm_node *node, int code_index, char code_digit)
+{
+	/* OR in index 1 or 2. */
+	node->next_code_index |= code_index;
+
+	if (!node->next_code_digits[0])
+		node->next_code_digits[0] = code_digit;
+	else if (node->next_code_digits[0] != code_digit)
+		node->next_code_digits[1] = code_digit;
+}
+
+
+/* Mark soundex code tree node as leaf. */
+static void
+set_leaf(dm_node *first_node[2], dm_node *last_node[2],
+		 dm_node *node, int ix_node)
+{
+	if (!node->is_leaf)
+	{
+		node->is_leaf = 1;
+
+		if (first_node[ix_node] == NULL)
+			first_node[ix_node] = node;
+		else
+			last_node[ix_node]->next[ix_node] = node;
+
+		last_node[ix_node] = node;
+		node->next[ix_node] = NULL;
+	}
+}
+
+
+/* Find next node corresponding to code digit, or create a new node. */
+static dm_node *
+find_or_create_child_node(dm_node *parent, char code_digit,
+						  ArrayBuildState *soundex)
+{
+	int			i = code_digit - '0';
+	dm_node   **nodes = parent->children;
+	dm_node    *node = nodes[i];
+
+	if (node)
+	{
+		/* Found existing child node. Skip completed nodes. */
+		return node->soundex_length < DM_CODE_DIGITS ? node : NULL;
+	}
+
+	/* Create new child node. */
+	node = palloc_object(dm_node);
+	nodes[i] = node;
+
+	*node = start_node;
+	memcpy(node->soundex, parent->soundex, sizeof(parent->soundex));
+	node->soundex_length = parent->soundex_length;
+	node->soundex[node->soundex_length++] = code_digit;
+	node->code_digit = code_digit;
+	node->next_code_index = node->prev_code_index;
+
+	if (node->soundex_length < DM_CODE_DIGITS)
+	{
+		return node;
+	}
+	else
+	{
+		/* Append completed soundex code to output array. */
+		text	   *out = cstring_to_text_with_len(node->soundex,
+												   DM_CODE_DIGITS);
+
+		accumArrayResult(soundex,
+						 PointerGetDatum(out),
+						 false,
+						 TEXTOID,
+						 CurrentMemoryContext);
+		return NULL;
+	}
+}
+
+
+/* Update node for next code digit(s). */
+static void
+update_node(dm_node *first_node[2], dm_node *last_node[2],
+			dm_node *node, int ix_node,
+			int letter_no, int prev_code_index, int next_code_index,
+			const char *next_code_digits, int digit_no,
+			ArrayBuildState *soundex)
+{
+	int			i;
+	char		next_code_digit = next_code_digits[digit_no];
+	int			num_dirty_nodes = 0;
+	dm_node    *dirty_nodes[2];
+
+	initialize_node(node, letter_no);
+
+	if (node->prev_code_index && !(node->prev_code_index & prev_code_index))
+	{
+		/*
+		 * If the sound (vowel / consonant) of this letter encoding doesn't
+		 * correspond to the coding index of the previous letter, we skip this
+		 * letter encoding. Note that currently, only "J" can be either a
+		 * vowel or a consonant.
+		 */
+		return;
+	}
+
+	if (next_code_digit == 'X' ||
+		(digit_no == 0 &&
+		 (node->prev_code_digits[0] == next_code_digit ||
+		  node->prev_code_digits[1] == next_code_digit)))
+	{
+		/* The code digit is the same as one of the previous (i.e. not added). */
+		dirty_nodes[num_dirty_nodes++] = node;
+	}
+
+	if (next_code_digit != 'X' &&
+		(digit_no > 0 ||
+		 node->prev_code_digits[0] != next_code_digit ||
+		 node->prev_code_digits[1]))
+	{
+		/* The code digit is different from one of the previous (i.e. added). */
+		node = find_or_create_child_node(node, next_code_digit, soundex);
+		if (node)
+		{
+			initialize_node(node, letter_no);
+			dirty_nodes[num_dirty_nodes++] = node;
+		}
+	}
+
+	for (i = 0; i < num_dirty_nodes; i++)
+	{
+		/* Add code digit leading to the current node. */
+		add_next_code_digit(dirty_nodes[i], next_code_index, next_code_digit);
+
+		if (next_code_digits[++digit_no])
+		{
+			update_node(first_node, last_node, dirty_nodes[i], ix_node,
+						letter_no, prev_code_index, next_code_index,
+						next_code_digits, digit_no,
+						soundex);
+		}
+		else
+		{
+			/* Add incomplete leaf node to linked list. */
+			set_leaf(first_node, last_node, dirty_nodes[i], ix_node);
+		}
+	}
+}
+
+
+/* Update soundex tree leaf nodes. */
+static void
+update_leaves(dm_node *first_node[2], int *ix_node, int letter_no,
+			  const dm_codes *codes, const dm_codes *next_codes,
+			  ArrayBuildState *soundex)
+{
+	int			i,
+				j,
+				code_index;
+	dm_node    *node,
+			   *last_node[2];
+	const dm_code *code,
+			   *next_code;
+	int			ix_node_next = (*ix_node + 1) & 1;	/* Alternating index: 0, 1 */
+
+	/* Initialize for new linked list of leaves. */
+	first_node[ix_node_next] = NULL;
+	last_node[ix_node_next] = NULL;
+
+	/* Process all nodes. */
+	for (node = first_node[*ix_node]; node; node = node->next[*ix_node])
+	{
+		/* One or two alternate code sequences. */
+		for (i = 0; i < 2 && (code = codes[i]) && code[0][0]; i++)
+		{
+			/* Coding for previous letter - before vowel: 1, all other: 2 */
+			int			prev_code_index = (code[0][0] > '1') + 1;
+
+			/* One or two alternate next code sequences. */
+			for (j = 0; j < 2 && (next_code = next_codes[j]) && next_code[0][0]; j++)
+			{
+				/* Determine which code to use. */
+				if (letter_no == 0)
+				{
+					/* This is the first letter. */
+					code_index = 0;
+				}
+				else if (next_code[0][0] <= '1')
+				{
+					/* The next letter is a vowel. */
+					code_index = 1;
+				}
+				else
+				{
+					/* All other cases. */
+					code_index = 2;
+				}
+
+				/* One or two sequential code digits. */
+				update_node(first_node, last_node, node, ix_node_next,
+							letter_no, prev_code_index, code_index,
+							code[code_index], 0,
+							soundex);
+			}
+		}
+	}
+
+	*ix_node = ix_node_next;
+}
+
+
+/*
+ * Return next character, converted from UTF-8 to uppercase ASCII.
+ * *ix is the current string index and is incremented by the character length.
+ */
+static char
+read_char(const unsigned char *str, int *ix)
+{
+	/* Substitute character for skipped code points. */
+	const char	na = '\x1a';
+	pg_wchar	c;
+
+	/* Decode UTF-8 character to ISO 10646 code point. */
+	str += *ix;
+	c = utf8_to_unicode(str);
+
+	/* Advance *ix, but (for safety) not if we've reached end of string. */
+	if (c)
+		*ix += pg_utf_mblen(str);
+
+	/* Convert. */
+	if (c >= (unsigned char) '[' && c <= (unsigned char) ']')
+	{
+		/* ASCII characters [, \, and ] are reserved for Ą, Ę, and Ţ/Ț. */
+		return na;
+	}
+	else if (c < 0x60)
+	{
+		/* Other non-lowercase ASCII characters can be used as-is. */
+		return (char) c;
+	}
+	else if (c < 0x100)
+	{
+		/* ISO-8859-1 code point; convert to upper-case ASCII via table. */
+		return iso8859_1_to_ascii_upper[c - 0x60];
+	}
+	else
+	{
+		/* Conversion of non-ASCII characters in the coding chart. */
+		switch (c)
+		{
+			case 0x0104:
+			case 0x0105:
+				/* Ą/ą */
+				return '[';
+			case 0x0118:
+			case 0x0119:
+				/* Ę/ę */
+				return '\\';
+			case 0x0162:
+			case 0x0163:
+			case 0x021A:
+			case 0x021B:
+				/* Ţ/ţ or Ț/ț */
+				return ']';
+			default:
+				return na;
+		}
+	}
+}
+
+
+/* Read next ASCII character, skipping any characters not in [A-\]]. */
+static char
+read_valid_char(const char *str, int *ix)
+{
+	char		c;
+
+	while ((c = read_char((const unsigned char *) str, ix)) != '\0')
+	{
+		if (c >= 'A' && c <= ']')
+			break;
+	}
+
+	return c;
+}
+
+
+/* Return sound coding for "letter" (letter sequence) */
+static const dm_codes *
+read_letter(const char *str, int *ix)
+{
+	char		c,
+				cmp;
+	int			i,
+				j;
+	const dm_letter *letters;
+	const dm_codes *codes;
+
+	/* First letter in sequence. */
+	if ((c = read_valid_char(str, ix)) == '\0')
+		return NULL;
+
+	letters = &letter_[c - 'A'];
+	codes = letters->codes;
+	i = *ix;
+
+	/* Any subsequent letters in sequence. */
+	while ((letters = letters->letters) && (c = read_valid_char(str, &i)))
+	{
+		for (j = 0; (cmp = letters[j].letter); j++)
+		{
+			if (cmp == c)
+			{
+				/* Letter found. */
+				letters = &letters[j];
+				if (letters->codes)
+				{
+					/* Coding for letter sequence found. */
+					codes = letters->codes;
+					*ix = i;
+				}
+				break;
+			}
+		}
+		if (!cmp)
+		{
+			/* The sequence of letters has no coding. */
+			break;
+		}
+	}
+
+	return codes;
+}
+
+
+/*
+ * Generate all Daitch-Mokotoff soundex codes for word,
+ * adding them to the "soundex" ArrayBuildState.
+ * Returns false if string has no encodable characters, else true.
+ */
+static bool
+daitch_mokotoff_coding(const char *word, ArrayBuildState *soundex)
+{
+	int			i = 0;
+	int			letter_no = 0;
+	int			ix_node = 0;
+	const dm_codes *codes,
+			   *next_codes;
+	dm_node    *first_node[2],
+			   *node;
+
+	/* First letter. */
+	if (!(codes = read_letter(word, &i)))
+	{
+		/* No encodable character in input. */
+		return false;
+	}
+
+	/* Starting point. */
+	first_node[ix_node] = palloc_object(dm_node);
+	*first_node[ix_node] = start_node;
+
+	/*
+	 * Loop until either the word input is exhausted, or all generated soundex
+	 * codes are completed to six digits.
+	 */
+	while (codes && first_node[ix_node])
+	{
+		next_codes = read_letter(word, &i);
+
+		/* Update leaf nodes. */
+		update_leaves(first_node, &ix_node, letter_no,
+					  codes, next_codes ? next_codes : end_codes,
+					  soundex);
+
+		codes = next_codes;
+		letter_no++;
+	}
+
+	/* Append all remaining (incomplete) soundex codes to output array. */
+	for (node = first_node[ix_node]; node; node = node->next[ix_node])
+	{
+		text	   *out = cstring_to_text_with_len(node->soundex,
+												   DM_CODE_DIGITS);
+
+		accumArrayResult(soundex,
+						 PointerGetDatum(out),
+						 false,
+						 TEXTOID,
+						 CurrentMemoryContext);
+	}
+
+	return true;
+}

contrib/fuzzystrmatch/daitch_mokotoff_header.pl

@@ -0,0 +1,223 @@
+#!/usr/bin/perl
+#
+# Generation of types and lookup tables for Daitch-Mokotoff soundex.
+#
+# Copyright (c) 2023, PostgreSQL Global Development Group
+#
+# This module was originally sponsored by Finance Norway /
+# Trafikkforsikringsforeningen, and implemented by Dag Lem <dag@nimrod.no>
+#
+
+use strict;
+use warnings;
+
+use utf8;
+use open IO => ':utf8', ':std';
+use Data::Dumper;
+
+die "Usage: $0 OUTPUT_FILE\n" if @ARGV != 1;
+my $output_file = $ARGV[0];
+
+# Open the output file
+open my $OUTPUT, '>', $output_file
+  or die "Could not open output file $output_file: $!\n";
+
+# Parse code table and generate tree for letter transitions.
+my %codes;
+my $table = [ {}, [ [ "", "", "" ] ] ];
+while (<DATA>)
+{
+	chomp;
+	my ($letters, $codes) = split(/\s+/);
+	my @codes = map { [ split(/,/) ] } split(/\|/, $codes);
+
+	my $key = "codes_" . join("_or_", map { join("_", @$_) } @codes);
+	my $val = join(
+		",\n",
+		map {
+			"\t{\n\t\t"
+			  . join(", ", map { "\"$_\"" } @$_) . "\n\t}"
+		} @codes);
+	$codes{$key} = $val;
+
+	for my $letter (split(/,/, $letters))
+	{
+		my $ref = $table->[0];
+		# Link each character to the next in the letter combination.
+		my @c = split(//, $letter);
+		my $last_c = pop(@c);
+		for my $c (@c)
+		{
+			$ref->{$c} //= [ {}, undef ];
+			$ref->{$c}[0] //= {};
+			$ref = $ref->{$c}[0];
+		}
+		# The sound code for the letter combination is stored at the last character.
+		$ref->{$last_c}[1] = $key;
+	}
+}
+close(DATA);
+
+print $OUTPUT <<EOF;
+/*
+ * Constants and lookup tables for Daitch-Mokotoff Soundex
+ *
+ * Copyright (c) 2023, PostgreSQL Global Development Group
+ *
+ * This file is generated by daitch_mokotoff_header.pl
+ */
+
+/* Coding chart table: Soundex codes */
+typedef char dm_code[2 + 1];	/* One or two sequential code digits + NUL */
+typedef dm_code dm_codes[3];	/* Start of name, before a vowel, any other */
+
+/* Coding chart table: Letter in input sequence */
+struct dm_letter
+{
+	char		letter;			/* Present letter in sequence */
+	const struct dm_letter *letters;	/* List of possible successive letters */
+	const dm_codes *codes;		/* Code sequence(s) for complete sequence */
+};
+
+typedef struct dm_letter dm_letter;
+
+/* Codes for letter sequence at start of name, before a vowel, and any other. */
+EOF
+
+for my $key (sort keys %codes)
+{
+	print $OUTPUT "static const dm_codes $key\[2\] =\n{\n"
+	  . $codes{$key}
+	  . "\n};\n";
+}
+
+print $OUTPUT <<EOF;
+
+/* Coding for alternative following letters in sequence. */
+EOF
+
+sub hash2code
+{
+	my ($ref, $letter) = @_;
+
+	my @letters = ();
+
+	my $h = $ref->[0];
+	for my $key (sort keys %$h)
+	{
+		$ref = $h->{$key};
+		my $children = "NULL";
+		if (defined $ref->[0])
+		{
+			$children = "letter_$letter$key";
+			hash2code($ref, "$letter$key");
+		}
+		my $codes = $ref->[1] // "NULL";
+		push(@letters, "\t{\n\t\t'$key', $children, $codes\n\t}");
+	}
+
+	print $OUTPUT "static const dm_letter letter_$letter\[\] =\n{\n";
+	for (@letters)
+	{
+		print $OUTPUT "$_,\n";
+	}
+	print $OUTPUT "\t{\n\t\t'\\0'\n\t}\n";
+	print $OUTPUT "};\n";
+}
+
+hash2code($table, '');
+
+close $OUTPUT;
+
+# Table adapted from https://www.jewishgen.org/InfoFiles/Soundex.html
+#
+# The conversion from the coding chart to the table should be self
+# explanatory, but note the differences stated below.
+#
+# X = NC (not coded)
+#
+# The non-ASCII letters in the coding chart are coded with substitute
+# lowercase ASCII letters, which sort after the uppercase ASCII letters:
+#
+# Ą => a (use '[' for table lookup)
+# Ę => e (use '\\' for table lookup)
+# Ţ => t (use ']' for table lookup)
+#
+# The rule for "UE" does not correspond to the coding chart, however
+# it is used by all other known implementations, including the one at
+# https://www.jewishgen.org/jos/jossound.htm (try e.g. "bouey").
+#
+# Note that the implementation assumes that vowels are assigned code
+# 0 or 1. "J" can be either a vowel or a consonant.
+#
+
+__DATA__
+AI,AJ,AY				0,1,X
+AU						0,7,X
+a						X,X,6|X,X,X
+A						0,X,X
+B						7,7,7
+CHS						5,54,54
+CH						5,5,5|4,4,4
+CK						5,5,5|45,45,45
+CZ,CS,CSZ,CZS			4,4,4
+C						5,5,5|4,4,4
+DRZ,DRS					4,4,4
+DS,DSH,DSZ				4,4,4
+DZ,DZH,DZS				4,4,4
+D,DT					3,3,3
+EI,EJ,EY				0,1,X
+EU						1,1,X
+e						X,X,6|X,X,X
+E						0,X,X
+FB						7,7,7
+F						7,7,7
+G						5,5,5
+H						5,5,X
+IA,IE,IO,IU				1,X,X
+I						0,X,X
+J						1,X,X|4,4,4
+KS						5,54,54
+KH						5,5,5
+K						5,5,5
+L						8,8,8
+MN						66,66,66
+M						6,6,6
+NM						66,66,66
+N						6,6,6
+OI,OJ,OY				0,1,X
+O						0,X,X
+P,PF,PH					7,7,7
+Q						5,5,5
+RZ,RS					94,94,94|4,4,4
+R						9,9,9
+SCHTSCH,SCHTSH,SCHTCH	2,4,4
+SCH						4,4,4
+SHTCH,SHCH,SHTSH		2,4,4
+SHT,SCHT,SCHD			2,43,43
+SH						4,4,4
+STCH,STSCH,SC			2,4,4
+STRZ,STRS,STSH			2,4,4
+ST						2,43,43
+SZCZ,SZCS				2,4,4
+SZT,SHD,SZD,SD			2,43,43
+SZ						4,4,4
+S						4,4,4
+TCH,TTCH,TTSCH			4,4,4
+TH						3,3,3
+TRZ,TRS					4,4,4
+TSCH,TSH				4,4,4
+TS,TTS,TTSZ,TC			4,4,4
+TZ,TTZ,TZS,TSZ			4,4,4
+t						3,3,3|4,4,4
+T						3,3,3
+UI,UJ,UY,UE				0,1,X
+U						0,X,X
+V						7,7,7
+W						7,7,7
+X						5,54,54
+Y						1,X,X
+ZDZ,ZDZH,ZHDZH			2,4,4
+ZD,ZHD					2,43,43
+ZH,ZS,ZSCH,ZSH			4,4,4
+Z						4,4,4

contrib/fuzzystrmatch/expected/fuzzystrmatch.out

@@ -65,3 +65,174 @@ SELECT dmetaphone_alt('gumbo');
  KMP
 (1 row)
 
+-- Wovels
+SELECT daitch_mokotoff('Augsburg');
+ daitch_mokotoff 
+-----------------
+ {054795}
+(1 row)
+
+SELECT daitch_mokotoff('Breuer');
+ daitch_mokotoff 
+-----------------
+ {791900}
+(1 row)
+
+SELECT daitch_mokotoff('Freud');
+ daitch_mokotoff 
+-----------------
+ {793000}
+(1 row)
+
+-- The letter "H"
+SELECT daitch_mokotoff('Halberstadt');
+ daitch_mokotoff 
+-----------------
+ {587943,587433}
+(1 row)
+
+SELECT daitch_mokotoff('Mannheim');
+ daitch_mokotoff 
+-----------------
+ {665600}
+(1 row)
+
+-- Adjacent sounds
+SELECT daitch_mokotoff('Chernowitz');
+ daitch_mokotoff 
+-----------------
+ {596740,496740}
+(1 row)
+
+-- Adjacent letters with identical adjacent code digits
+SELECT daitch_mokotoff('Cherkassy');
+ daitch_mokotoff 
+-----------------
+ {595400,495400}
+(1 row)
+
+SELECT daitch_mokotoff('Kleinman');
+ daitch_mokotoff 
+-----------------
+ {586660}
+(1 row)
+
+-- More than one word
+SELECT daitch_mokotoff('Nowy Targ');
+ daitch_mokotoff 
+-----------------
+ {673950}
+(1 row)
+
+-- Padded with "0"
+SELECT daitch_mokotoff('Berlin');
+ daitch_mokotoff 
+-----------------
+ {798600}
+(1 row)
+
+-- Other examples from https://www.avotaynu.com/soundex.htm
+SELECT daitch_mokotoff('Ceniow');
+ daitch_mokotoff 
+-----------------
+ {567000,467000}
+(1 row)
+
+SELECT daitch_mokotoff('Tsenyuv');
+ daitch_mokotoff 
+-----------------
+ {467000}
+(1 row)
+
+SELECT daitch_mokotoff('Holubica');
+ daitch_mokotoff 
+-----------------
+ {587500,587400}
+(1 row)
+
+SELECT daitch_mokotoff('Golubitsa');
+ daitch_mokotoff 
+-----------------
+ {587400}
+(1 row)
+
+SELECT daitch_mokotoff('Przemysl');
+ daitch_mokotoff 
+-----------------
+ {794648,746480}
+(1 row)
+
+SELECT daitch_mokotoff('Pshemeshil');
+ daitch_mokotoff 
+-----------------
+ {746480}
+(1 row)
+
+SELECT daitch_mokotoff('Rosochowaciec');
+                      daitch_mokotoff                      
+-----------------------------------------------------------
+ {945755,945754,945745,945744,944755,944754,944745,944744}
+(1 row)
+
+SELECT daitch_mokotoff('Rosokhovatsets');
+ daitch_mokotoff 
+-----------------
+ {945744}
+(1 row)
+
+-- Ignored characters
+SELECT daitch_mokotoff('''OBrien');
+ daitch_mokotoff 
+-----------------
+ {079600}
+(1 row)
+
+SELECT daitch_mokotoff('O''Brien');
+ daitch_mokotoff 
+-----------------
+ {079600}
+(1 row)
+
+-- "Difficult" cases, likely to cause trouble for other implementations.
+SELECT daitch_mokotoff('CJC');
+               daitch_mokotoff               
+---------------------------------------------
+ {550000,540000,545000,450000,400000,440000}
+(1 row)
+
+SELECT daitch_mokotoff('BESST');
+ daitch_mokotoff 
+-----------------
+ {743000}
+(1 row)
+
+SELECT daitch_mokotoff('BOUEY');
+ daitch_mokotoff 
+-----------------
+ {710000}
+(1 row)
+
+SELECT daitch_mokotoff('HANNMANN');
+ daitch_mokotoff 
+-----------------
+ {566600}
+(1 row)
+
+SELECT daitch_mokotoff('MCCOYJR');
+                      daitch_mokotoff                      
+-----------------------------------------------------------
+ {651900,654900,654190,654490,645190,645490,641900,644900}
+(1 row)
+
+SELECT daitch_mokotoff('ACCURSO');
+                      daitch_mokotoff                      
+-----------------------------------------------------------
+ {059400,054000,054940,054400,045940,045400,049400,044000}
+(1 row)
+
+SELECT daitch_mokotoff('BIERSCHBACH');
+                      daitch_mokotoff                      
+-----------------------------------------------------------
+ {794575,794574,794750,794740,745750,745740,747500,747400}
+(1 row)
+

contrib/fuzzystrmatch/expected/fuzzystrmatch_utf8.out

@@ -0,0 +1,61 @@
+/*
+ * This test must be run in a database with UTF-8 encoding,
+ * because other encodings don't support all the characters used.
+ */
+SELECT getdatabaseencoding() <> 'UTF8'
+       AS skip_test \gset
+\if :skip_test
+\quit
+\endif
+set client_encoding = utf8;
+-- CREATE EXTENSION IF NOT EXISTS fuzzystrmatch;
+-- Accents
+SELECT daitch_mokotoff('Müller');
+ daitch_mokotoff 
+-----------------
+ {689000}
+(1 row)
+
+SELECT daitch_mokotoff('Schäfer');
+ daitch_mokotoff 
+-----------------
+ {479000}
+(1 row)
+
+SELECT daitch_mokotoff('Straßburg');
+ daitch_mokotoff 
+-----------------
+ {294795}
+(1 row)
+
+SELECT daitch_mokotoff('Éregon');
+ daitch_mokotoff 
+-----------------
+ {095600}
+(1 row)
+
+-- Special characters added at https://www.jewishgen.org/InfoFiles/Soundex.html
+SELECT daitch_mokotoff('gąszczu');
+ daitch_mokotoff 
+-----------------
+ {564000,540000}
+(1 row)
+
+SELECT daitch_mokotoff('brzęczy');
+        daitch_mokotoff        
+-------------------------------
+ {794640,794400,746400,744000}
+(1 row)
+
+SELECT daitch_mokotoff('ţamas');
+ daitch_mokotoff 
+-----------------
+ {364000,464000}
+(1 row)
+
+SELECT daitch_mokotoff('țamas');
+ daitch_mokotoff 
+-----------------
+ {364000,464000}
+(1 row)
+

contrib/fuzzystrmatch/expected/fuzzystrmatch_utf8_1.out

@@ -0,0 +1,8 @@
+/*
+ * This test must be run in a database with UTF-8 encoding,
+ * because other encodings don't support all the characters used.
+ */
+SELECT getdatabaseencoding() <> 'UTF8'
+       AS skip_test \gset
+\if :skip_test
+\quit

contrib/fuzzystrmatch/fuzzystrmatch--1.1--1.2.sql

@@ -0,0 +1,8 @@
+/* contrib/fuzzystrmatch/fuzzystrmatch--1.1--1.2.sql */
+
+-- complain if script is sourced in psql, rather than via ALTER EXTENSION
+\echo Use "ALTER EXTENSION fuzzystrmatch UPDATE TO '1.2'" to load this file. \quit
+
+CREATE FUNCTION daitch_mokotoff(text) RETURNS text[]
+AS 'MODULE_PATHNAME', 'daitch_mokotoff'
+LANGUAGE C IMMUTABLE STRICT PARALLEL SAFE;

contrib/fuzzystrmatch/fuzzystrmatch.control

@@ -1,6 +1,6 @@
 # fuzzystrmatch extension
 comment = 'determine similarities and distance between strings'
-default_version = '1.1'
+default_version = '1.2'
 module_pathname = '$libdir/fuzzystrmatch'
 relocatable = true
 trusted = true

contrib/fuzzystrmatch/meson.build

@@ -1,10 +1,19 @@
 # Copyright (c) 2022-2023, PostgreSQL Global Development Group
 
 fuzzystrmatch_sources = files(
-  'fuzzystrmatch.c',
+  'daitch_mokotoff.c',
   'dmetaphone.c',
+  'fuzzystrmatch.c',
 )
 
+daitch_mokotoff_h = custom_target('daitch_mokotoff',
+  input: 'daitch_mokotoff_header.pl',
+  output: 'daitch_mokotoff.h',
+  command: [perl, '@INPUT@', '@OUTPUT@'],
+)
+generated_sources += daitch_mokotoff_h
+fuzzystrmatch_sources += daitch_mokotoff_h
+
 if host_system == 'windows'
   fuzzystrmatch_sources += rc_lib_gen.process(win32ver_rc, extra_args: [
     '--NAME', 'fuzzystrmatch',
@@ -13,6 +22,7 @@ endif
 
 fuzzystrmatch = shared_module('fuzzystrmatch',
   fuzzystrmatch_sources,
+  include_directories: include_directories('.'),
   kwargs: contrib_mod_args,
 )
 contrib_targets += fuzzystrmatch
@@ -21,6 +31,7 @@ install_data(
   'fuzzystrmatch.control',
   'fuzzystrmatch--1.0--1.1.sql',
   'fuzzystrmatch--1.1.sql',
+  'fuzzystrmatch--1.1--1.2.sql',
   kwargs: contrib_data_args,
 )
 
@@ -31,6 +42,7 @@ tests += {
   'regress': {
     'sql': [
       'fuzzystrmatch',
+      'fuzzystrmatch_utf8',
     ],
   },
 }

contrib/fuzzystrmatch/sql/fuzzystrmatch.sql

@@ -19,3 +19,48 @@ SELECT metaphone('GUMBO', 4);
 
 SELECT dmetaphone('gumbo');
 SELECT dmetaphone_alt('gumbo');
+
+-- Wovels
+SELECT daitch_mokotoff('Augsburg');
+SELECT daitch_mokotoff('Breuer');
+SELECT daitch_mokotoff('Freud');
+
+-- The letter "H"
+SELECT daitch_mokotoff('Halberstadt');
+SELECT daitch_mokotoff('Mannheim');
+
+-- Adjacent sounds
+SELECT daitch_mokotoff('Chernowitz');
+
+-- Adjacent letters with identical adjacent code digits
+SELECT daitch_mokotoff('Cherkassy');
+SELECT daitch_mokotoff('Kleinman');
+
+-- More than one word
+SELECT daitch_mokotoff('Nowy Targ');
+
+-- Padded with "0"
+SELECT daitch_mokotoff('Berlin');
+
+-- Other examples from https://www.avotaynu.com/soundex.htm
+SELECT daitch_mokotoff('Ceniow');
+SELECT daitch_mokotoff('Tsenyuv');
+SELECT daitch_mokotoff('Holubica');
+SELECT daitch_mokotoff('Golubitsa');
+SELECT daitch_mokotoff('Przemysl');
+SELECT daitch_mokotoff('Pshemeshil');
+SELECT daitch_mokotoff('Rosochowaciec');
+SELECT daitch_mokotoff('Rosokhovatsets');
+
+-- Ignored characters
+SELECT daitch_mokotoff('''OBrien');
+SELECT daitch_mokotoff('O''Brien');
+
+-- "Difficult" cases, likely to cause trouble for other implementations.
+SELECT daitch_mokotoff('CJC');
+SELECT daitch_mokotoff('BESST');
+SELECT daitch_mokotoff('BOUEY');
+SELECT daitch_mokotoff('HANNMANN');
+SELECT daitch_mokotoff('MCCOYJR');
+SELECT daitch_mokotoff('ACCURSO');
+SELECT daitch_mokotoff('BIERSCHBACH');

contrib/fuzzystrmatch/sql/fuzzystrmatch_utf8.sql

@@ -0,0 +1,26 @@
+/*
+ * This test must be run in a database with UTF-8 encoding,
+ * because other encodings don't support all the characters used.
+ */
+
+SELECT getdatabaseencoding() <> 'UTF8'
+       AS skip_test \gset
+\if :skip_test
+\quit
+\endif
+
+set client_encoding = utf8;
+
+-- CREATE EXTENSION IF NOT EXISTS fuzzystrmatch;
+
+-- Accents
+SELECT daitch_mokotoff('Müller');
+SELECT daitch_mokotoff('Schäfer');
+SELECT daitch_mokotoff('Straßburg');
+SELECT daitch_mokotoff('Éregon');
+
+-- Special characters added at https://www.jewishgen.org/InfoFiles/Soundex.html
+SELECT daitch_mokotoff('gąszczu');
+SELECT daitch_mokotoff('brzęczy');
+SELECT daitch_mokotoff('ţamas');
+SELECT daitch_mokotoff('țamas');

doc/src/sgml/fuzzystrmatch.sgml

@@ -17,6 +17,8 @@
    At present, the <function>soundex</function>, <function>metaphone</function>,
    <function>dmetaphone</function>, and <function>dmetaphone_alt</function> functions do
    not work well with multibyte encodings (such as UTF-8).
+   Use <function>daitch_mokotoff</function>
+   or <function>levenshtein</function> with such data.
   </para>
  </caution>
 
@@ -88,6 +90,159 @@ SELECT * FROM s WHERE difference(s.nm, 'john') &gt; 2;
 </programlisting>
  </sect2>
 
+ <sect2 id="fuzzystrmatch-daitch-mokotoff">
+  <title>Daitch-Mokotoff Soundex</title>
+
+  <para>
+   Like the original Soundex system, Daitch-Mokotoff Soundex matches
+   similar-sounding names by converting them to the same code.
+   However, Daitch-Mokotoff Soundex is significantly more useful for
+   non-English names than the original system.
+   Major improvements over the original system include:
+
+   <itemizedlist spacing="compact" mark="bullet">
+    <listitem>
+     <para>
+      The code is based on the first six meaningful letters rather than four.
+     </para>
+    </listitem>
+    <listitem>
+     <para>
+      A letter or combination of letters maps into ten possible codes rather
+      than seven.
+     </para>
+    </listitem>
+    <listitem>
+     <para>
+      Where two consecutive letters have a single sound, they are coded as a
+      single number.
+     </para>
+    </listitem>
+    <listitem>
+     <para>
+      When a letter or combination of letters may have different sounds,
+      multiple codes are emitted to cover all possibilities.
+     </para>
+    </listitem>
+   </itemizedlist>
+  </para>
+
+  <indexterm>
+   <primary>daitch_mokotoff</primary>
+  </indexterm>
+
+  <para>
+   This function generates the Daitch-Mokotoff soundex codes for its input:
+  </para>
+
+<synopsis>
+daitch_mokotoff(<parameter>source</parameter> text) returns text[]
+</synopsis>
+
+  <para>
+   The result may contain one or more codes depending on how many plausible
+   pronunciations there are, so it is represented as an array.
+  </para>
+
+  <para>
+   Since a Daitch-Mokotoff soundex code consists of only 6 digits,
+   <parameter>source</parameter> should be preferably a single word or name.
+  </para>
+
+  <para>
+   Here are some examples:
+  </para>
+
+<programlisting>
+SELECT daitch_mokotoff('George');
+ daitch_mokotoff
+-----------------
+ {595000}
+
+SELECT daitch_mokotoff('John');
+ daitch_mokotoff
+-----------------
+ {160000,460000}
+
+SELECT daitch_mokotoff('Bierschbach');
+                      daitch_mokotoff
+-----------------------------------------------------------
+ {794575,794574,794750,794740,745750,745740,747500,747400}
+
+SELECT daitch_mokotoff('Schwartzenegger');
+ daitch_mokotoff
+-----------------
+ {479465}
+</programlisting>
+
+  <para>
+   For matching of single names, returned text arrays can be matched
+   directly using the <literal>&amp;&amp;</literal> operator: any overlap
+   can be considered a match.  A GIN index may
+   be used for efficiency, see <xref linkend="gin"/> and this example:
+  </para>
+
+<programlisting>
+CREATE TABLE s (nm text);
+CREATE INDEX ix_s_dm ON s USING gin (daitch_mokotoff(nm)) WITH (fastupdate = off);
+
+INSERT INTO s (nm) VALUES
+  ('Schwartzenegger'),
+  ('John'),
+  ('James'),
+  ('Steinman'),
+  ('Steinmetz');
+
+SELECT * FROM s WHERE daitch_mokotoff(nm) &amp;&amp; daitch_mokotoff('Swartzenegger');
+SELECT * FROM s WHERE daitch_mokotoff(nm) &amp;&amp; daitch_mokotoff('Jane');
+SELECT * FROM s WHERE daitch_mokotoff(nm) &amp;&amp; daitch_mokotoff('Jens');
+</programlisting>
+
+  <para>
+   For indexing and matching of any number of names in any order, Full Text
+   Search features can be used. See <xref linkend="textsearch"/> and this
+   example:
+  </para>
+
+<programlisting>
+CREATE FUNCTION soundex_tsvector(v_name text) RETURNS tsvector
+BEGIN ATOMIC
+  SELECT to_tsvector('simple',
+                     string_agg(array_to_string(daitch_mokotoff(n), ' '), ' '))
+  FROM regexp_split_to_table(v_name, '\s+') AS n;
+END;
+
+CREATE FUNCTION soundex_tsquery(v_name text) RETURNS tsquery
+BEGIN ATOMIC
+  SELECT string_agg('(' || array_to_string(daitch_mokotoff(n), '|') || ')', '&amp;')::tsquery
+  FROM regexp_split_to_table(v_name, '\s+') AS n;
+END;
+
+CREATE TABLE s (nm text);
+CREATE INDEX ix_s_txt ON s USING gin (soundex_tsvector(nm)) WITH (fastupdate = off);
+
+INSERT INTO s (nm) VALUES
+  ('John Doe'),
+  ('Jane Roe'),
+  ('Public John Q.'),
+  ('George Best'),
+  ('John Yamson');
+
+SELECT * FROM s WHERE soundex_tsvector(nm) @@ soundex_tsquery('john');
+SELECT * FROM s WHERE soundex_tsvector(nm) @@ soundex_tsquery('jane doe');
+SELECT * FROM s WHERE soundex_tsvector(nm) @@ soundex_tsquery('john public');
+SELECT * FROM s WHERE soundex_tsvector(nm) @@ soundex_tsquery('besst, giorgio');
+SELECT * FROM s WHERE soundex_tsvector(nm) @@ soundex_tsquery('Jameson John');
+</programlisting>
+
+  <para>
+   If it is desired to avoid recalculation of soundex codes during index
+   rechecks, an index on a separate column can be used instead of an index on
+   an expression.  A stored generated column can be used for this; see
+   <xref linkend="ddl-generated-columns"/>.
+  </para>
+ </sect2>
+
  <sect2 id="fuzzystrmatch-levenshtein">
   <title>Levenshtein</title>
 
@@ -104,10 +259,10 @@ SELECT * FROM s WHERE difference(s.nm, 'john') &gt; 2;
   </indexterm>
 
 <synopsis>
-levenshtein(text source, text target, int ins_cost, int del_cost, int sub_cost) returns int
-levenshtein(text source, text target) returns int
-levenshtein_less_equal(text source, text target, int ins_cost, int del_cost, int sub_cost, int max_d) returns int
-levenshtein_less_equal(text source, text target, int max_d) returns int
+levenshtein(source text, target text, ins_cost int, del_cost int, sub_cost int) returns int
+levenshtein(source text, target text) returns int
+levenshtein_less_equal(source text, target text, ins_cost int, del_cost int, sub_cost int, max_d int) returns int
+levenshtein_less_equal(source text, target text, max_d int) returns int
 </synopsis>
 
   <para>
@@ -177,7 +332,7 @@ test=# SELECT levenshtein_less_equal('extensive', 'exhaustive', 4);
   </indexterm>
 
 <synopsis>
-metaphone(text source, int max_output_length) returns text
+metaphone(source text, max_output_length int) returns text
 </synopsis>
 
   <para>
@@ -220,8 +375,8 @@ test=# SELECT metaphone('GUMBO', 4);
   </indexterm>
 
 <synopsis>
-dmetaphone(text source) returns text
-dmetaphone_alt(text source) returns text
+dmetaphone(source text) returns text
+dmetaphone_alt(source text) returns text
 </synopsis>
 
   <para>