dict_snowball.c

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/*-------------------------------------------------------------------------
 *
 * dict_snowball.c
 *      Snowball dictionary
 *
 * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
 *
 * IDENTIFICATION
 *    src/backend/snowball/dict_snowball.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"
 
#include "catalog/pg_collation_d.h"
#include "commands/defrem.h"
#include "mb/pg_wchar.h"
#include "tsearch/ts_public.h"
#include "utils/formatting.h"
 
/* Some platforms define MAXINT and/or MININT, causing conflicts */
#ifdef MAXINT
#undef MAXINT
#endif
#ifdef MININT
#undef MININT
#endif
 
/* Now we can include the original Snowball header.h */
#include "snowball/libstemmer/header.h"
#include "snowball/libstemmer/stem_ISO_8859_1_basque.h"
#include "snowball/libstemmer/stem_ISO_8859_1_catalan.h"
#include "snowball/libstemmer/stem_ISO_8859_1_danish.h"
#include "snowball/libstemmer/stem_ISO_8859_1_dutch.h"
#include "snowball/libstemmer/stem_ISO_8859_1_english.h"
#include "snowball/libstemmer/stem_ISO_8859_1_finnish.h"
#include "snowball/libstemmer/stem_ISO_8859_1_french.h"
#include "snowball/libstemmer/stem_ISO_8859_1_german.h"
#include "snowball/libstemmer/stem_ISO_8859_1_indonesian.h"
#include "snowball/libstemmer/stem_ISO_8859_1_irish.h"
#include "snowball/libstemmer/stem_ISO_8859_1_italian.h"
#include "snowball/libstemmer/stem_ISO_8859_1_norwegian.h"
#include "snowball/libstemmer/stem_ISO_8859_1_porter.h"
#include "snowball/libstemmer/stem_ISO_8859_1_portuguese.h"
#include "snowball/libstemmer/stem_ISO_8859_1_spanish.h"
#include "snowball/libstemmer/stem_ISO_8859_1_swedish.h"
#include "snowball/libstemmer/stem_ISO_8859_2_hungarian.h"
#include "snowball/libstemmer/stem_KOI8_R_russian.h"
#include "snowball/libstemmer/stem_UTF_8_arabic.h"
#include "snowball/libstemmer/stem_UTF_8_armenian.h"
#include "snowball/libstemmer/stem_UTF_8_basque.h"
#include "snowball/libstemmer/stem_UTF_8_catalan.h"
#include "snowball/libstemmer/stem_UTF_8_danish.h"
#include "snowball/libstemmer/stem_UTF_8_dutch.h"
#include "snowball/libstemmer/stem_UTF_8_english.h"
#include "snowball/libstemmer/stem_UTF_8_estonian.h"
#include "snowball/libstemmer/stem_UTF_8_finnish.h"
#include "snowball/libstemmer/stem_UTF_8_french.h"
#include "snowball/libstemmer/stem_UTF_8_german.h"
#include "snowball/libstemmer/stem_UTF_8_greek.h"
#include "snowball/libstemmer/stem_UTF_8_hindi.h"
#include "snowball/libstemmer/stem_UTF_8_hungarian.h"
#include "snowball/libstemmer/stem_UTF_8_indonesian.h"
#include "snowball/libstemmer/stem_UTF_8_irish.h"
#include "snowball/libstemmer/stem_UTF_8_italian.h"
#include "snowball/libstemmer/stem_UTF_8_lithuanian.h"
#include "snowball/libstemmer/stem_UTF_8_nepali.h"
#include "snowball/libstemmer/stem_UTF_8_norwegian.h"
#include "snowball/libstemmer/stem_UTF_8_porter.h"
#include "snowball/libstemmer/stem_UTF_8_portuguese.h"
#include "snowball/libstemmer/stem_UTF_8_romanian.h"
#include "snowball/libstemmer/stem_UTF_8_russian.h"
#include "snowball/libstemmer/stem_UTF_8_serbian.h"
#include "snowball/libstemmer/stem_UTF_8_spanish.h"
#include "snowball/libstemmer/stem_UTF_8_swedish.h"
#include "snowball/libstemmer/stem_UTF_8_tamil.h"
#include "snowball/libstemmer/stem_UTF_8_turkish.h"
#include "snowball/libstemmer/stem_UTF_8_yiddish.h"
 
PG_MODULE_MAGIC_EXT(
                    .name = "dict_snowball",
                    .version = PG_VERSION
);
 
PG_FUNCTION_INFO_V1(dsnowball_init);
 
PG_FUNCTION_INFO_V1(dsnowball_lexize);
 
/* List of supported modules */
typedef struct stemmer_module
{
    const char *name;
    pg_enc      enc;
    struct SN_env *(*create) (void);
    void        (*close) (struct SN_env *);
    int         (*stem) (struct SN_env *);
} stemmer_module;
 
/* Args: stemmer name, PG code for encoding, Snowball's name for encoding */
#define STEMMER_MODULE(name,enc,senc) \
    {#name, enc, name##_##senc##_create_env, name##_##senc##_close_env, name##_##senc##_stem}
 
static const stemmer_module stemmer_modules[] =
{
    /*
     * Stemmers list from Snowball distribution
     */
    STEMMER_MODULE(basque, PG_LATIN1, ISO_8859_1),
    STEMMER_MODULE(catalan, PG_LATIN1, ISO_8859_1),
    STEMMER_MODULE(danish, PG_LATIN1, ISO_8859_1),
    STEMMER_MODULE(dutch, PG_LATIN1, ISO_8859_1),
    STEMMER_MODULE(english, PG_LATIN1, ISO_8859_1),
    STEMMER_MODULE(finnish, PG_LATIN1, ISO_8859_1),
    STEMMER_MODULE(french, PG_LATIN1, ISO_8859_1),
    STEMMER_MODULE(german, PG_LATIN1, ISO_8859_1),
    STEMMER_MODULE(indonesian, PG_LATIN1, ISO_8859_1),
    STEMMER_MODULE(irish, PG_LATIN1, ISO_8859_1),
    STEMMER_MODULE(italian, PG_LATIN1, ISO_8859_1),
    STEMMER_MODULE(norwegian, PG_LATIN1, ISO_8859_1),
    STEMMER_MODULE(porter, PG_LATIN1, ISO_8859_1),
    STEMMER_MODULE(portuguese, PG_LATIN1, ISO_8859_1),
    STEMMER_MODULE(spanish, PG_LATIN1, ISO_8859_1),
    STEMMER_MODULE(swedish, PG_LATIN1, ISO_8859_1),
    STEMMER_MODULE(hungarian, PG_LATIN2, ISO_8859_2),
    STEMMER_MODULE(russian, PG_KOI8R, KOI8_R),
    STEMMER_MODULE(arabic, PG_UTF8, UTF_8),
    STEMMER_MODULE(armenian, PG_UTF8, UTF_8),
    STEMMER_MODULE(basque, PG_UTF8, UTF_8),
    STEMMER_MODULE(catalan, PG_UTF8, UTF_8),
    STEMMER_MODULE(danish, PG_UTF8, UTF_8),
    STEMMER_MODULE(dutch, PG_UTF8, UTF_8),
    STEMMER_MODULE(english, PG_UTF8, UTF_8),
    STEMMER_MODULE(estonian, PG_UTF8, UTF_8),
    STEMMER_MODULE(finnish, PG_UTF8, UTF_8),
    STEMMER_MODULE(french, PG_UTF8, UTF_8),
    STEMMER_MODULE(german, PG_UTF8, UTF_8),
    STEMMER_MODULE(greek, PG_UTF8, UTF_8),
    STEMMER_MODULE(hindi, PG_UTF8, UTF_8),
    STEMMER_MODULE(hungarian, PG_UTF8, UTF_8),
    STEMMER_MODULE(indonesian, PG_UTF8, UTF_8),
    STEMMER_MODULE(irish, PG_UTF8, UTF_8),
    STEMMER_MODULE(italian, PG_UTF8, UTF_8),
    STEMMER_MODULE(lithuanian, PG_UTF8, UTF_8),
    STEMMER_MODULE(nepali, PG_UTF8, UTF_8),
    STEMMER_MODULE(norwegian, PG_UTF8, UTF_8),
    STEMMER_MODULE(porter, PG_UTF8, UTF_8),
    STEMMER_MODULE(portuguese, PG_UTF8, UTF_8),
    STEMMER_MODULE(romanian, PG_UTF8, UTF_8),
    STEMMER_MODULE(russian, PG_UTF8, UTF_8),
    STEMMER_MODULE(serbian, PG_UTF8, UTF_8),
    STEMMER_MODULE(spanish, PG_UTF8, UTF_8),
    STEMMER_MODULE(swedish, PG_UTF8, UTF_8),
    STEMMER_MODULE(tamil, PG_UTF8, UTF_8),
    STEMMER_MODULE(turkish, PG_UTF8, UTF_8),
    STEMMER_MODULE(yiddish, PG_UTF8, UTF_8),
 
    /*
     * Stemmer with PG_SQL_ASCII encoding should be valid for any server
     * encoding
     */
    STEMMER_MODULE(english, PG_SQL_ASCII, ISO_8859_1),
 
    {NULL, 0, NULL, NULL, NULL} /* list end marker */
};
 
 
typedef struct DictSnowball
{
    struct SN_env *z;
    StopList    stoplist;
    bool        needrecode;     /* needs recoding before/after call stem */
    int         (*stem) (struct SN_env *z);
 
    /*
     * snowball saves alloced memory between calls, so we should run it in our
     * private memory context. Note, init function is executed in long lived
     * context, so we just remember CurrentMemoryContext
     */
    MemoryContext dictCtx;
} DictSnowball;
 
 
static void
locate_stem_module(DictSnowball *d, const char *lang)
{
    const stemmer_module *m;
 
    /*
     * First, try to find exact match of stemmer module. Stemmer with
     * PG_SQL_ASCII encoding is treated as working with any server encoding
     */
    for (m = stemmer_modules; m->name; m++)
    {
        if ((m->enc == PG_SQL_ASCII || m->enc == GetDatabaseEncoding()) &&
            pg_strcasecmp(m->name, lang) == 0)
        {
            d->stem = m->stem;
            d->z = m->create();
            d->needrecode = false;
            return;
        }
    }
 
    /*
     * Second, try to find stemmer for needed language for UTF8 encoding.
     */
    for (m = stemmer_modules; m->name; m++)
    {
        if (m->enc == PG_UTF8 && pg_strcasecmp(m->name, lang) == 0)
        {
            d->stem = m->stem;
            d->z = m->create();
            d->needrecode = true;
            return;
        }
    }
 
    ereport(ERROR,
            (errcode(ERRCODE_UNDEFINED_OBJECT),
             errmsg("no Snowball stemmer available for language \"%s\" and encoding \"%s\"",
                    lang, GetDatabaseEncodingName())));
}
 
Datum
dsnowball_init(PG_FUNCTION_ARGS)
{
    List       *dictoptions = (List *) PG_GETARG_POINTER(0);
    DictSnowball *d;
    bool        stoploaded = false;
    ListCell   *l;
 
    d = (DictSnowball *) palloc0(sizeof(DictSnowball));
 
    foreach(l, dictoptions)
    {
        DefElem    *defel = (DefElem *) lfirst(l);
 
        if (strcmp(defel->defname, "stopwords") == 0)
        {
            if (stoploaded)
                ereport(ERROR,
                        (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                         errmsg("multiple StopWords parameters")));
            readstoplist(defGetString(defel), &d->stoplist, str_tolower);
            stoploaded = true;
        }
        else if (strcmp(defel->defname, "language") == 0)
        {
            if (d->stem)
                ereport(ERROR,
                        (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                         errmsg("multiple Language parameters")));
            locate_stem_module(d, defGetString(defel));
        }
        else
        {
            ereport(ERROR,
                    (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                     errmsg("unrecognized Snowball parameter: \"%s\"",
                            defel->defname)));
        }
    }
 
    if (!d->stem)
        ereport(ERROR,
                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                 errmsg("missing Language parameter")));
 
    d->dictCtx = CurrentMemoryContext;
 
    PG_RETURN_POINTER(d);
}
 
Datum
dsnowball_lexize(PG_FUNCTION_ARGS)
{
    DictSnowball *d = (DictSnowball *) PG_GETARG_POINTER(0);
    char       *in = (char *) PG_GETARG_POINTER(1);
    int32       len = PG_GETARG_INT32(2);
    char       *txt = str_tolower(in, len, DEFAULT_COLLATION_OID);
    TSLexeme   *res = palloc0(sizeof(TSLexeme) * 2);
 
    /*
     * Do not pass strings exceeding 1000 bytes to the stemmer, as they're
     * surely not words in any human language.  This restriction avoids
     * wasting cycles on stuff like base64-encoded data, and it protects us
     * against possible inefficiency or misbehavior in the stemmer.  (For
     * example, the Turkish stemmer has an indefinite recursion, so it can
     * crash on long-enough strings.)  However, Snowball dictionaries are
     * defined to recognize all strings, so we can't reject the string as an
     * unknown word.
     */
    if (len > 1000)
    {
        /* return the lexeme lowercased, but otherwise unmodified */
        res->lexeme = txt;
    }
    else if (*txt == '\0' || searchstoplist(&(d->stoplist), txt))
    {
        /* empty or stopword, so report as stopword */
        pfree(txt);
    }
    else
    {
        MemoryContext saveCtx;
 
        /*
         * recode to utf8 if stemmer is utf8 and doesn't match server encoding
         */
        if (d->needrecode)
        {
            char       *recoded;
 
            recoded = pg_server_to_any(txt, strlen(txt), PG_UTF8);
            if (recoded != txt)
            {
                pfree(txt);
                txt = recoded;
            }
        }
 
        /* see comment about d->dictCtx */
        saveCtx = MemoryContextSwitchTo(d->dictCtx);
        SN_set_current(d->z, strlen(txt), (symbol *) txt);
        d->stem(d->z);
        MemoryContextSwitchTo(saveCtx);
 
        if (d->z->p && d->z->l)
        {
            txt = repalloc(txt, d->z->l + 1);
            memcpy(txt, d->z->p, d->z->l);
            txt[d->z->l] = '\0';
        }
 
        /* back recode if needed */
        if (d->needrecode)
        {
            char       *recoded;
 
            recoded = pg_any_to_server(txt, strlen(txt), PG_UTF8);
            if (recoded != txt)
            {
                pfree(txt);
                txt = recoded;
            }
        }
 
        res->lexeme = txt;
    }
 
    PG_RETURN_POINTER(res);
}