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postgresql/contrib/fuzzystrmatch/daitch_mokotoff.c

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/*
* Daitch-Mokotoff Soundex
*
* Copyright (c) 2023-2024, 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{|}~ ! ?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 conversions below. */
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: /* LATIN CAPITAL LETTER A WITH OGONEK */
case 0x0105: /* LATIN SMALL LETTER A WITH OGONEK */
return '[';
case 0x0118: /* LATIN CAPITAL LETTER E WITH OGONEK */
case 0x0119: /* LATIN SMALL LETTER E WITH OGONEK */
return '\\';
case 0x0162: /* LATIN CAPITAL LETTER T WITH CEDILLA */
case 0x0163: /* LATIN SMALL LETTER T WITH CEDILLA */
case 0x021A: /* LATIN CAPITAL LETTER T WITH COMMA BELOW */
case 0x021B: /* LATIN SMALL LETTER T WITH COMMA BELOW */
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;
}
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