dict_snowball.c

Go to the documentation of this file.

/*-------------------------------------------------------------------------
 *
 * dict_snowball.c
 *      Snowball dictionary
 *
 * Portions Copyright (c) 1996-2013, PostgreSQL Global Development Group
 *
 * IDENTIFICATION
 *    src/backend/snowball/dict_snowball.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include "commands/defrem.h"
#include "tsearch/ts_locale.h"
#include "tsearch/ts_utils.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_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_hungarian.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_romanian.h"
#include "snowball/libstemmer/stem_KOI8_R_russian.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_finnish.h"
#include "snowball/libstemmer/stem_UTF_8_french.h"
#include "snowball/libstemmer/stem_UTF_8_german.h"
#include "snowball/libstemmer/stem_UTF_8_hungarian.h"
#include "snowball/libstemmer/stem_UTF_8_italian.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_spanish.h"
#include "snowball/libstemmer/stem_UTF_8_swedish.h"
#include "snowball/libstemmer/stem_UTF_8_turkish.h"


PG_MODULE_MAGIC;

PG_FUNCTION_INFO_V1(dsnowball_init);
Datum       dsnowball_init(PG_FUNCTION_ARGS);

PG_FUNCTION_INFO_V1(dsnowball_lexize);
Datum       dsnowball_lexize(PG_FUNCTION_ARGS);

/* 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;

static const stemmer_module stemmer_modules[] =
{
    /*
     * Stemmers list from Snowball distribution
     */
    {"danish", PG_LATIN1, danish_ISO_8859_1_create_env, danish_ISO_8859_1_close_env, danish_ISO_8859_1_stem},
    {"dutch", PG_LATIN1, dutch_ISO_8859_1_create_env, dutch_ISO_8859_1_close_env, dutch_ISO_8859_1_stem},
    {"english", PG_LATIN1, english_ISO_8859_1_create_env, english_ISO_8859_1_close_env, english_ISO_8859_1_stem},
    {"finnish", PG_LATIN1, finnish_ISO_8859_1_create_env, finnish_ISO_8859_1_close_env, finnish_ISO_8859_1_stem},
    {"french", PG_LATIN1, french_ISO_8859_1_create_env, french_ISO_8859_1_close_env, french_ISO_8859_1_stem},
    {"german", PG_LATIN1, german_ISO_8859_1_create_env, german_ISO_8859_1_close_env, german_ISO_8859_1_stem},
    {"hungarian", PG_LATIN1, hungarian_ISO_8859_1_create_env, hungarian_ISO_8859_1_close_env, hungarian_ISO_8859_1_stem},
    {"italian", PG_LATIN1, italian_ISO_8859_1_create_env, italian_ISO_8859_1_close_env, italian_ISO_8859_1_stem},
    {"norwegian", PG_LATIN1, norwegian_ISO_8859_1_create_env, norwegian_ISO_8859_1_close_env, norwegian_ISO_8859_1_stem},
    {"porter", PG_LATIN1, porter_ISO_8859_1_create_env, porter_ISO_8859_1_close_env, porter_ISO_8859_1_stem},
    {"portuguese", PG_LATIN1, portuguese_ISO_8859_1_create_env, portuguese_ISO_8859_1_close_env, portuguese_ISO_8859_1_stem},
    {"spanish", PG_LATIN1, spanish_ISO_8859_1_create_env, spanish_ISO_8859_1_close_env, spanish_ISO_8859_1_stem},
    {"swedish", PG_LATIN1, swedish_ISO_8859_1_create_env, swedish_ISO_8859_1_close_env, swedish_ISO_8859_1_stem},
    {"romanian", PG_LATIN2, romanian_ISO_8859_2_create_env, romanian_ISO_8859_2_close_env, romanian_ISO_8859_2_stem},
    {"russian", PG_KOI8R, russian_KOI8_R_create_env, russian_KOI8_R_close_env, russian_KOI8_R_stem},
    {"danish", PG_UTF8, danish_UTF_8_create_env, danish_UTF_8_close_env, danish_UTF_8_stem},
    {"dutch", PG_UTF8, dutch_UTF_8_create_env, dutch_UTF_8_close_env, dutch_UTF_8_stem},
    {"english", PG_UTF8, english_UTF_8_create_env, english_UTF_8_close_env, english_UTF_8_stem},
    {"finnish", PG_UTF8, finnish_UTF_8_create_env, finnish_UTF_8_close_env, finnish_UTF_8_stem},
    {"french", PG_UTF8, french_UTF_8_create_env, french_UTF_8_close_env, french_UTF_8_stem},
    {"german", PG_UTF8, german_UTF_8_create_env, german_UTF_8_close_env, german_UTF_8_stem},
    {"hungarian", PG_UTF8, hungarian_UTF_8_create_env, hungarian_UTF_8_close_env, hungarian_UTF_8_stem},
    {"italian", PG_UTF8, italian_UTF_8_create_env, italian_UTF_8_close_env, italian_UTF_8_stem},
    {"norwegian", PG_UTF8, norwegian_UTF_8_create_env, norwegian_UTF_8_close_env, norwegian_UTF_8_stem},
    {"porter", PG_UTF8, porter_UTF_8_create_env, porter_UTF_8_close_env, porter_UTF_8_stem},
    {"portuguese", PG_UTF8, portuguese_UTF_8_create_env, portuguese_UTF_8_close_env, portuguese_UTF_8_stem},
    {"romanian", PG_UTF8, romanian_UTF_8_create_env, romanian_UTF_8_close_env, romanian_UTF_8_stem},
    {"russian", PG_UTF8, russian_UTF_8_create_env, russian_UTF_8_close_env, russian_UTF_8_stem},
    {"spanish", PG_UTF8, spanish_UTF_8_create_env, spanish_UTF_8_close_env, spanish_UTF_8_stem},
    {"swedish", PG_UTF8, swedish_UTF_8_create_env, swedish_UTF_8_close_env, swedish_UTF_8_stem},
    {"turkish", PG_UTF8, turkish_UTF_8_create_env, turkish_UTF_8_close_env, turkish_UTF_8_stem},

    /*
     * Stemmer with PG_SQL_ASCII encoding should be valid for any server
     * encoding
     */
    {"english", PG_SQL_ASCII, english_ISO_8859_1_create_env, english_ISO_8859_1_close_env, english_ISO_8859_1_stem},

    {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, 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 (pg_strcasecmp("StopWords", defel->defname) == 0)
        {
            if (stoploaded)
                ereport(ERROR,
                        (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                         errmsg("multiple StopWords parameters")));
            readstoplist(defGetString(defel), &d->stoplist, lowerstr);
            stoploaded = true;
        }
        else if (pg_strcasecmp("Language", defel->defname) == 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 = lowerstr_with_len(in, len);
    TSLexeme   *res = palloc0(sizeof(TSLexeme) * 2);

    if (*txt == '\0' || searchstoplist(&(d->stoplist), txt))
    {
        pfree(txt);
    }
    else
    {
        MemoryContext saveCtx;

        /*
         * recode to utf8 if stemmer is utf8 and doesn't match server encoding
         */
        if (d->needrecode)
        {
            char       *recoded;

            recoded = (char *) pg_do_encoding_conversion((unsigned char *) txt,
                                                         strlen(txt),
                                                       GetDatabaseEncoding(),
                                                         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 = (char *) pg_do_encoding_conversion((unsigned char *) txt,
                                                         strlen(txt),
                                                         PG_UTF8,
                                                      GetDatabaseEncoding());
            if (recoded != txt)
            {
                pfree(txt);
                txt = recoded;
            }
        }

        res->lexeme = txt;
    }

    PG_RETURN_POINTER(res);
}