tsrank.c

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/*-------------------------------------------------------------------------
 *
 * tsrank.c
 *      rank tsvector by tsquery
 *
 * Portions Copyright (c) 1996-2026, PostgreSQL Global Development Group
 *
 *
 * IDENTIFICATION
 *    src/backend/utils/adt/tsrank.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"
 
#include <limits.h>
#include <math.h>
 
#include "miscadmin.h"
#include "tsearch/ts_utils.h"
#include "utils/array.h"
#include "utils/fmgrprotos.h"
 
#define NUM_WEIGHTS 4
static const float default_weights[NUM_WEIGHTS] = {0.1f, 0.2f, 0.4f, 1.0f};
 
#define wpos(wep)   ( w[ WEP_GETWEIGHT(wep) ] )
 
#define RANK_NO_NORM            0x00
#define RANK_NORM_LOGLENGTH     0x01
#define RANK_NORM_LENGTH        0x02
#define RANK_NORM_EXTDIST       0x04
#define RANK_NORM_UNIQ          0x08
#define RANK_NORM_LOGUNIQ       0x10
#define RANK_NORM_RDIVRPLUS1    0x20
#define DEF_NORM_METHOD         RANK_NO_NORM
 
static float calc_rank_or(const float *w, TSVector t, TSQuery q);
static float calc_rank_and(const float *w, TSVector t, TSQuery q);
 
/*
 * Returns a weight of a word collocation
 */
static float4
word_distance(int32 w)
{
    if (w > 100)
        return 1e-30f;
 
    return 1.0 / (1.005 + 0.05 * exp(((float4) w) / 1.5 - 2));
}
 
static int
cnt_length(TSVector t)
{
    WordEntry  *ptr = ARRPTR(t),
               *end = (WordEntry *) STRPTR(t);
    int         len = 0;
 
    while (ptr < end)
    {
        int         clen = POSDATALEN(t, ptr);
 
        if (clen == 0)
            len += 1;
        else
            len += clen;
 
        ptr++;
    }
 
    return len;
}
 
 
#define WordECompareQueryItem(e,q,p,i,m) \
    tsCompareString((q) + (i)->distance, (i)->length,   \
                    (e) + (p)->pos, (p)->len, (m))
 
 
/*
 * Returns a pointer to a WordEntry's array corresponding to 'item' from
 * tsvector 't'. 'q' is the TSQuery containing 'item'.
 * Returns NULL if not found.
 */
static WordEntry *
find_wordentry(TSVector t, TSQuery q, QueryOperand *item, int32 *nitem)
{
    WordEntry  *StopLow = ARRPTR(t);
    WordEntry  *StopHigh = (WordEntry *) STRPTR(t);
    WordEntry  *StopMiddle = StopHigh;
    int         difference;
 
    *nitem = 0;
 
    /* Loop invariant: StopLow <= item < StopHigh */
    while (StopLow < StopHigh)
    {
        StopMiddle = StopLow + (StopHigh - StopLow) / 2;
        difference = WordECompareQueryItem(STRPTR(t), GETOPERAND(q), StopMiddle, item, false);
        if (difference == 0)
        {
            StopHigh = StopMiddle;
            *nitem = 1;
            break;
        }
        else if (difference > 0)
            StopLow = StopMiddle + 1;
        else
            StopHigh = StopMiddle;
    }
 
    if (item->prefix)
    {
        if (StopLow >= StopHigh)
            StopMiddle = StopHigh;
 
        *nitem = 0;
 
        while (StopMiddle < (WordEntry *) STRPTR(t) &&
               WordECompareQueryItem(STRPTR(t), GETOPERAND(q), StopMiddle, item, true) == 0)
        {
            (*nitem)++;
            StopMiddle++;
        }
    }
 
    return (*nitem > 0) ? StopHigh : NULL;
}
 
 
/*
 * sort QueryOperands by (length, word)
 */
static int
compareQueryOperand(const void *a, const void *b, void *arg)
{
    char       *operand = (char *) arg;
    QueryOperand *qa = (*(QueryOperand *const *) a);
    QueryOperand *qb = (*(QueryOperand *const *) b);
 
    return tsCompareString(operand + qa->distance, qa->length,
                           operand + qb->distance, qb->length,
                           false);
}
 
/*
 * Returns a sorted, de-duplicated array of QueryOperands in a query.
 * The returned QueryOperands are pointers to the original QueryOperands
 * in the query.
 *
 * Length of the returned array is stored in *size
 */
static QueryOperand **
SortAndUniqItems(TSQuery q, int *size)
{
    char       *operand = GETOPERAND(q);
    QueryItem  *item = GETQUERY(q);
    QueryOperand **res,
              **ptr,
              **prevptr;
 
    ptr = res = palloc_array(QueryOperand *, *size);
 
    /* Collect all operands from the tree to res */
    while ((*size)--)
    {
        if (item->type == QI_VAL)
        {
            *ptr = (QueryOperand *) item;
            ptr++;
        }
        item++;
    }
 
    *size = ptr - res;
    if (*size < 2)
        return res;
 
    qsort_arg(res, *size, sizeof(QueryOperand *), compareQueryOperand, operand);
 
    ptr = res + 1;
    prevptr = res;
 
    /* remove duplicates */
    while (ptr - res < *size)
    {
        if (compareQueryOperand(ptr, prevptr, operand) != 0)
        {
            prevptr++;
            *prevptr = *ptr;
        }
        ptr++;
    }
 
    *size = prevptr + 1 - res;
    return res;
}
 
static float
calc_rank_and(const float *w, TSVector t, TSQuery q)
{
    WordEntryPosVector **pos;
    WordEntryPosVector1 posnull;
    WordEntryPosVector *POSNULL;
    int         i,
                k,
                l,
                p;
    WordEntry  *entry,
               *firstentry;
    WordEntryPos *post,
               *ct;
    int32       dimt,
                lenct,
                dist,
                nitem;
    float       res = -1.0;
    QueryOperand **item;
    int         size = q->size;
 
    item = SortAndUniqItems(q, &size);
    if (size < 2)
    {
        pfree(item);
        return calc_rank_or(w, t, q);
    }
    pos = palloc0_array(WordEntryPosVector *, q->size);
 
    /* A dummy WordEntryPos array to use when haspos is false */
    posnull.npos = 1;
    posnull.pos[0] = 0;
    WEP_SETPOS(posnull.pos[0], MAXENTRYPOS - 1);
    POSNULL = (WordEntryPosVector *) &posnull;
 
    for (i = 0; i < size; i++)
    {
        firstentry = entry = find_wordentry(t, q, item[i], &nitem);
        if (!entry)
            continue;
 
        while (entry - firstentry < nitem)
        {
            if (entry->haspos)
                pos[i] = _POSVECPTR(t, entry);
            else
                pos[i] = POSNULL;
 
            dimt = pos[i]->npos;
            post = pos[i]->pos;
            for (k = 0; k < i; k++)
            {
                if (!pos[k])
                    continue;
                lenct = pos[k]->npos;
                ct = pos[k]->pos;
                for (l = 0; l < dimt; l++)
                {
                    for (p = 0; p < lenct; p++)
                    {
                        dist = abs((int) WEP_GETPOS(post[l]) - (int) WEP_GETPOS(ct[p]));
                        if (dist || (dist == 0 && (pos[i] == POSNULL || pos[k] == POSNULL)))
                        {
                            float       curw;
 
                            if (!dist)
                                dist = MAXENTRYPOS;
                            curw = sqrt(wpos(post[l]) * wpos(ct[p]) * word_distance(dist));
                            res = (res < 0) ? curw : 1.0 - (1.0 - res) * (1.0 - curw);
                        }
                    }
                }
            }
 
            entry++;
        }
    }
    pfree(pos);
    pfree(item);
    return res;
}
 
static float
calc_rank_or(const float *w, TSVector t, TSQuery q)
{
    WordEntry  *entry,
               *firstentry;
    WordEntryPosVector1 posnull;
    WordEntryPos *post;
    int32       dimt,
                j,
                i,
                nitem;
    float       res = 0.0;
    QueryOperand **item;
    int         size = q->size;
 
    /* A dummy WordEntryPos array to use when haspos is false */
    posnull.npos = 1;
    posnull.pos[0] = 0;
 
    item = SortAndUniqItems(q, &size);
 
    for (i = 0; i < size; i++)
    {
        float       resj,
                    wjm;
        int32       jm;
 
        firstentry = entry = find_wordentry(t, q, item[i], &nitem);
        if (!entry)
            continue;
 
        while (entry - firstentry < nitem)
        {
            if (entry->haspos)
            {
                dimt = POSDATALEN(t, entry);
                post = POSDATAPTR(t, entry);
            }
            else
            {
                dimt = posnull.npos;
                post = posnull.pos;
            }
 
            resj = 0.0;
            wjm = -1.0;
            jm = 0;
            for (j = 0; j < dimt; j++)
            {
                resj = resj + wpos(post[j]) / ((j + 1) * (j + 1));
                if (wpos(post[j]) > wjm)
                {
                    wjm = wpos(post[j]);
                    jm = j;
                }
            }
/*
            limit (sum(1/i^2),i=1,inf) = pi^2/6
            resj = sum(wi/i^2),i=1,noccurrence,
            wi - should be sorted desc,
            don't sort for now, just choose maximum weight. This should be corrected
            Oleg Bartunov
*/
            res = res + (wjm + resj - wjm / ((jm + 1) * (jm + 1))) / 1.64493406685;
 
            entry++;
        }
    }
    if (size > 0)
        res = res / size;
    pfree(item);
    return res;
}
 
static float
calc_rank(const float *w, TSVector t, TSQuery q, int32 method)
{
    QueryItem  *item = GETQUERY(q);
    float       res = 0.0;
    int         len;
 
    if (!t->size || !q->size)
        return 0.0;
 
    /* XXX: What about NOT? */
    res = (item->type == QI_OPR && (item->qoperator.oper == OP_AND ||
                                    item->qoperator.oper == OP_PHRASE)) ?
        calc_rank_and(w, t, q) :
        calc_rank_or(w, t, q);
 
    if (res < 0)
        res = 1e-20f;
 
    if ((method & RANK_NORM_LOGLENGTH) && t->size > 0)
        res /= log((double) (cnt_length(t) + 1)) / log(2.0);
 
    if (method & RANK_NORM_LENGTH)
    {
        len = cnt_length(t);
        if (len > 0)
            res /= (float) len;
    }
 
    /* RANK_NORM_EXTDIST not applicable */
 
    if ((method & RANK_NORM_UNIQ) && t->size > 0)
        res /= (float) (t->size);
 
    if ((method & RANK_NORM_LOGUNIQ) && t->size > 0)
        res /= log((double) (t->size + 1)) / log(2.0);
 
    if (method & RANK_NORM_RDIVRPLUS1)
        res /= (res + 1);
 
    return res;
}
 
/*
 * Extract weights from an array. The weights are stored in *ws, which must
 * have space for NUM_WEIGHTS elements.
 */
static void
getWeights(ArrayType *win, float *ws)
{
    int         i;
    float4     *arrdata;
 
    Assert(win != NULL);
 
    if (ARR_NDIM(win) != 1)
        ereport(ERROR,
                (errcode(ERRCODE_ARRAY_SUBSCRIPT_ERROR),
                 errmsg("array of weight must be one-dimensional")));
 
    if (ArrayGetNItems(ARR_NDIM(win), ARR_DIMS(win)) < NUM_WEIGHTS)
        ereport(ERROR,
                (errcode(ERRCODE_ARRAY_SUBSCRIPT_ERROR),
                 errmsg("array of weight is too short")));
 
    if (array_contains_nulls(win))
        ereport(ERROR,
                (errcode(ERRCODE_NULL_VALUE_NOT_ALLOWED),
                 errmsg("array of weight must not contain nulls")));
 
    arrdata = (float4 *) ARR_DATA_PTR(win);
    for (i = 0; i < NUM_WEIGHTS; i++)
    {
        ws[i] = (arrdata[i] >= 0) ? arrdata[i] : default_weights[i];
        if (ws[i] > 1.0)
            ereport(ERROR,
                    (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                     errmsg("weight out of range")));
    }
}
 
Datum
ts_rank_wttf(PG_FUNCTION_ARGS)
{
    ArrayType  *win = (ArrayType *) PG_DETOAST_DATUM(PG_GETARG_DATUM(0));
    TSVector    txt = PG_GETARG_TSVECTOR(1);
    TSQuery     query = PG_GETARG_TSQUERY(2);
    int         method = PG_GETARG_INT32(3);
    float       weights[NUM_WEIGHTS];
    float       res;
 
    getWeights(win, weights);
    res = calc_rank(weights, txt, query, method);
 
    PG_FREE_IF_COPY(win, 0);
    PG_FREE_IF_COPY(txt, 1);
    PG_FREE_IF_COPY(query, 2);
    PG_RETURN_FLOAT4(res);
}
 
Datum
ts_rank_wtt(PG_FUNCTION_ARGS)
{
    ArrayType  *win = (ArrayType *) PG_DETOAST_DATUM(PG_GETARG_DATUM(0));
    TSVector    txt = PG_GETARG_TSVECTOR(1);
    TSQuery     query = PG_GETARG_TSQUERY(2);
    float       weights[NUM_WEIGHTS];
    float       res;
 
    getWeights(win, weights);
    res = calc_rank(weights, txt, query, DEF_NORM_METHOD);
 
    PG_FREE_IF_COPY(win, 0);
    PG_FREE_IF_COPY(txt, 1);
    PG_FREE_IF_COPY(query, 2);
    PG_RETURN_FLOAT4(res);
}
 
Datum
ts_rank_ttf(PG_FUNCTION_ARGS)
{
    TSVector    txt = PG_GETARG_TSVECTOR(0);
    TSQuery     query = PG_GETARG_TSQUERY(1);
    int         method = PG_GETARG_INT32(2);
    float       res;
 
    res = calc_rank(default_weights, txt, query, method);
 
    PG_FREE_IF_COPY(txt, 0);
    PG_FREE_IF_COPY(query, 1);
    PG_RETURN_FLOAT4(res);
}
 
Datum
ts_rank_tt(PG_FUNCTION_ARGS)
{
    TSVector    txt = PG_GETARG_TSVECTOR(0);
    TSQuery     query = PG_GETARG_TSQUERY(1);
    float       res;
 
    res = calc_rank(default_weights, txt, query, DEF_NORM_METHOD);
 
    PG_FREE_IF_COPY(txt, 0);
    PG_FREE_IF_COPY(query, 1);
    PG_RETURN_FLOAT4(res);
}
 
typedef struct
{
    union
    {
        struct
        {                       /* compiled doc representation */
            QueryItem **items;
            int16       nitem;
        }           query;
        struct
        {                       /* struct is used for preparing doc
                                 * representation */
            QueryItem  *item;
            WordEntry  *entry;
        }           map;
    }           data;
    WordEntryPos pos;
} DocRepresentation;
 
static int
compareDocR(const void *va, const void *vb)
{
    const DocRepresentation *a = (const DocRepresentation *) va;
    const DocRepresentation *b = (const DocRepresentation *) vb;
 
    if (WEP_GETPOS(a->pos) == WEP_GETPOS(b->pos))
    {
        if (WEP_GETWEIGHT(a->pos) == WEP_GETWEIGHT(b->pos))
        {
            if (a->data.map.entry == b->data.map.entry)
                return 0;
 
            return (a->data.map.entry > b->data.map.entry) ? 1 : -1;
        }
 
        return (WEP_GETWEIGHT(a->pos) > WEP_GETWEIGHT(b->pos)) ? 1 : -1;
    }
 
    return (WEP_GETPOS(a->pos) > WEP_GETPOS(b->pos)) ? 1 : -1;
}
 
#define MAXQROPOS   MAXENTRYPOS
typedef struct
{
    bool        operandexists;
    bool        reverseinsert;  /* indicates insert order, true means
                                 * descending order */
    uint32      npos;
    WordEntryPos pos[MAXQROPOS];
} QueryRepresentationOperand;
 
typedef struct
{
    TSQuery     query;
    QueryRepresentationOperand *operandData;
} QueryRepresentation;
 
#define QR_GET_OPERAND_DATA(q, v) \
    ( (q)->operandData + (((QueryItem*)(v)) - GETQUERY((q)->query)) )
 
/*
 * TS_execute callback for matching a tsquery operand to QueryRepresentation
 */
static TSTernaryValue
checkcondition_QueryOperand(void *checkval, QueryOperand *val,
                            ExecPhraseData *data)
{
    QueryRepresentation *qr = (QueryRepresentation *) checkval;
    QueryRepresentationOperand *opData = QR_GET_OPERAND_DATA(qr, val);
 
    if (!opData->operandexists)
        return TS_NO;
 
    if (data)
    {
        data->npos = opData->npos;
        data->pos = opData->pos;
        if (opData->reverseinsert)
            data->pos += MAXQROPOS - opData->npos;
    }
 
    return TS_YES;
}
 
typedef struct
{
    int         pos;
    int         p;
    int         q;
    DocRepresentation *begin;
    DocRepresentation *end;
} CoverExt;
 
static void
resetQueryRepresentation(QueryRepresentation *qr, bool reverseinsert)
{
    int         i;
 
    for (i = 0; i < qr->query->size; i++)
    {
        qr->operandData[i].operandexists = false;
        qr->operandData[i].reverseinsert = reverseinsert;
        qr->operandData[i].npos = 0;
    }
}
 
static void
fillQueryRepresentationData(QueryRepresentation *qr, DocRepresentation *entry)
{
    int         i;
    int         lastPos;
    QueryRepresentationOperand *opData;
 
    for (i = 0; i < entry->data.query.nitem; i++)
    {
        if (entry->data.query.items[i]->type != QI_VAL)
            continue;
 
        opData = QR_GET_OPERAND_DATA(qr, entry->data.query.items[i]);
 
        opData->operandexists = true;
 
        if (opData->npos == 0)
        {
            lastPos = (opData->reverseinsert) ? (MAXQROPOS - 1) : 0;
            opData->pos[lastPos] = entry->pos;
            opData->npos++;
            continue;
        }
 
        lastPos = opData->reverseinsert ?
            (MAXQROPOS - opData->npos) :
            (opData->npos - 1);
 
        if (WEP_GETPOS(opData->pos[lastPos]) != WEP_GETPOS(entry->pos))
        {
            lastPos = opData->reverseinsert ?
                (MAXQROPOS - 1 - opData->npos) :
                (opData->npos);
 
            opData->pos[lastPos] = entry->pos;
            opData->npos++;
        }
    }
}
 
static bool
Cover(DocRepresentation *doc, int len, QueryRepresentation *qr, CoverExt *ext)
{
    DocRepresentation *ptr;
    int         lastpos = ext->pos;
    bool        found = false;
 
    /*
     * since this function recurses, it could be driven to stack overflow.
     * (though any decent compiler will optimize away the tail-recursion.
     */
    check_stack_depth();
 
    resetQueryRepresentation(qr, false);
 
    ext->p = INT_MAX;
    ext->q = 0;
    ptr = doc + ext->pos;
 
    /* find upper bound of cover from current position, move up */
    while (ptr - doc < len)
    {
        fillQueryRepresentationData(qr, ptr);
 
        if (TS_execute(GETQUERY(qr->query), qr,
                       TS_EXEC_EMPTY, checkcondition_QueryOperand))
        {
            if (WEP_GETPOS(ptr->pos) > ext->q)
            {
                ext->q = WEP_GETPOS(ptr->pos);
                ext->end = ptr;
                lastpos = ptr - doc;
                found = true;
            }
            break;
        }
        ptr++;
    }
 
    if (!found)
        return false;
 
    resetQueryRepresentation(qr, true);
 
    ptr = doc + lastpos;
 
    /* find lower bound of cover from found upper bound, move down */
    while (ptr >= doc + ext->pos)
    {
        /*
         * we scan doc from right to left, so pos info in reverse order!
         */
        fillQueryRepresentationData(qr, ptr);
 
        if (TS_execute(GETQUERY(qr->query), qr,
                       TS_EXEC_EMPTY, checkcondition_QueryOperand))
        {
            if (WEP_GETPOS(ptr->pos) < ext->p)
            {
                ext->begin = ptr;
                ext->p = WEP_GETPOS(ptr->pos);
            }
            break;
        }
        ptr--;
    }
 
    if (ext->p <= ext->q)
    {
        /*
         * set position for next try to next lexeme after beginning of found
         * cover
         */
        ext->pos = (ptr - doc) + 1;
        return true;
    }
 
    ext->pos++;
    return Cover(doc, len, qr, ext);
}
 
static DocRepresentation *
get_docrep(TSVector txt, QueryRepresentation *qr, int *doclen)
{
    QueryItem  *item = GETQUERY(qr->query);
    WordEntry  *entry,
               *firstentry;
    WordEntryPos *post;
    int32       dimt,           /* number of 'post' items */
                j,
                i,
                nitem;
    int         len = qr->query->size * 4,
                cur = 0;
    DocRepresentation *doc;
 
    doc = palloc_array(DocRepresentation, len);
 
    /*
     * Iterate through query to make DocRepresentation for words and it's
     * entries satisfied by query
     */
    for (i = 0; i < qr->query->size; i++)
    {
        QueryOperand *curoperand;
 
        if (item[i].type != QI_VAL)
            continue;
 
        curoperand = &item[i].qoperand;
 
        firstentry = entry = find_wordentry(txt, qr->query, curoperand, &nitem);
        if (!entry)
            continue;
 
        /* iterations over entries in tsvector */
        while (entry - firstentry < nitem)
        {
            if (entry->haspos)
            {
                dimt = POSDATALEN(txt, entry);
                post = POSDATAPTR(txt, entry);
            }
            else
            {
                /* ignore words without positions */
                entry++;
                continue;
            }
 
            while (cur + dimt >= len)
            {
                len *= 2;
                doc = (DocRepresentation *) repalloc(doc, sizeof(DocRepresentation) * len);
            }
 
            /* iterations over entry's positions */
            for (j = 0; j < dimt; j++)
            {
                if (curoperand->weight == 0 ||
                    curoperand->weight & (1 << WEP_GETWEIGHT(post[j])))
                {
                    doc[cur].pos = post[j];
                    doc[cur].data.map.entry = entry;
                    doc[cur].data.map.item = (QueryItem *) curoperand;
                    cur++;
                }
            }
 
            entry++;
        }
    }
 
    if (cur > 0)
    {
        DocRepresentation *rptr = doc + 1,
                   *wptr = doc,
                    storage;
 
        /*
         * Sort representation in ascending order by pos and entry
         */
        qsort(doc, cur, sizeof(DocRepresentation), compareDocR);
 
        /*
         * Join QueryItem per WordEntry and its position
         */
        storage.pos = doc->pos;
        storage.data.query.items = palloc_array(QueryItem *, qr->query->size);
        storage.data.query.items[0] = doc->data.map.item;
        storage.data.query.nitem = 1;
 
        while (rptr - doc < cur)
        {
            if (rptr->pos == (rptr - 1)->pos &&
                rptr->data.map.entry == (rptr - 1)->data.map.entry)
            {
                storage.data.query.items[storage.data.query.nitem] = rptr->data.map.item;
                storage.data.query.nitem++;
            }
            else
            {
                *wptr = storage;
                wptr++;
                storage.pos = rptr->pos;
                storage.data.query.items = palloc_array(QueryItem *, qr->query->size);
                storage.data.query.items[0] = rptr->data.map.item;
                storage.data.query.nitem = 1;
            }
 
            rptr++;
        }
 
        *wptr = storage;
        wptr++;
 
        *doclen = wptr - doc;
        return doc;
    }
 
    pfree(doc);
    return NULL;
}
 
static float4
calc_rank_cd(const float4 *arrdata, TSVector txt, TSQuery query, int method)
{
    DocRepresentation *doc;
    int         len,
                i,
                doclen = 0;
    CoverExt    ext;
    double      Wdoc = 0.0;
    double      invws[NUM_WEIGHTS];
    double      SumDist = 0.0,
                PrevExtPos = 0.0;
    int         NExtent = 0;
    QueryRepresentation qr;
 
 
    for (i = 0; i < NUM_WEIGHTS; i++)
    {
        invws[i] = ((double) ((arrdata[i] >= 0) ? arrdata[i] : default_weights[i]));
        if (invws[i] > 1.0)
            ereport(ERROR,
                    (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                     errmsg("weight out of range")));
        invws[i] = 1.0 / invws[i];
    }
 
    qr.query = query;
    qr.operandData = palloc0_array(QueryRepresentationOperand, query->size);
 
    doc = get_docrep(txt, &qr, &doclen);
    if (!doc)
    {
        pfree(qr.operandData);
        return 0.0;
    }
 
    MemSet(&ext, 0, sizeof(CoverExt));
    while (Cover(doc, doclen, &qr, &ext))
    {
        double      Cpos = 0.0;
        double      InvSum = 0.0;
        double      CurExtPos;
        int         nNoise;
        DocRepresentation *ptr = ext.begin;
 
        while (ptr <= ext.end)
        {
            InvSum += invws[WEP_GETWEIGHT(ptr->pos)];
            ptr++;
        }
 
        Cpos = ((double) (ext.end - ext.begin + 1)) / InvSum;
 
        /*
         * if doc are big enough then ext.q may be equal to ext.p due to limit
         * of positional information. In this case we approximate number of
         * noise word as half cover's length
         */
        nNoise = (ext.q - ext.p) - (ext.end - ext.begin);
        if (nNoise < 0)
            nNoise = (ext.end - ext.begin) / 2;
        Wdoc += Cpos / ((double) (1 + nNoise));
 
        CurExtPos = ((double) (ext.q + ext.p)) / 2.0;
        if (NExtent > 0 && CurExtPos > PrevExtPos   /* prevent division by
                                                     * zero in a case of
              * multiple lexize */ )
            SumDist += 1.0 / (CurExtPos - PrevExtPos);
 
        PrevExtPos = CurExtPos;
        NExtent++;
    }
 
    if ((method & RANK_NORM_LOGLENGTH) && txt->size > 0)
        Wdoc /= log((double) (cnt_length(txt) + 1));
 
    if (method & RANK_NORM_LENGTH)
    {
        len = cnt_length(txt);
        if (len > 0)
            Wdoc /= (double) len;
    }
 
    if ((method & RANK_NORM_EXTDIST) && NExtent > 0 && SumDist > 0)
        Wdoc /= ((double) NExtent) / SumDist;
 
    if ((method & RANK_NORM_UNIQ) && txt->size > 0)
        Wdoc /= (double) (txt->size);
 
    if ((method & RANK_NORM_LOGUNIQ) && txt->size > 0)
        Wdoc /= log((double) (txt->size + 1)) / log(2.0);
 
    if (method & RANK_NORM_RDIVRPLUS1)
        Wdoc /= (Wdoc + 1);
 
    pfree(doc);
 
    pfree(qr.operandData);
 
    return (float4) Wdoc;
}
 
Datum
ts_rankcd_wttf(PG_FUNCTION_ARGS)
{
    ArrayType  *win = (ArrayType *) PG_DETOAST_DATUM(PG_GETARG_DATUM(0));
    TSVector    txt = PG_GETARG_TSVECTOR(1);
    TSQuery     query = PG_GETARG_TSQUERY(2);
    int         method = PG_GETARG_INT32(3);
    float       weights[NUM_WEIGHTS];
    float       res;
 
    getWeights(win, weights);
    res = calc_rank_cd(weights, txt, query, method);
 
    PG_FREE_IF_COPY(win, 0);
    PG_FREE_IF_COPY(txt, 1);
    PG_FREE_IF_COPY(query, 2);
    PG_RETURN_FLOAT4(res);
}
 
Datum
ts_rankcd_wtt(PG_FUNCTION_ARGS)
{
    ArrayType  *win = (ArrayType *) PG_DETOAST_DATUM(PG_GETARG_DATUM(0));
    TSVector    txt = PG_GETARG_TSVECTOR(1);
    TSQuery     query = PG_GETARG_TSQUERY(2);
    float       weights[NUM_WEIGHTS];
    float       res;
 
    getWeights(win, weights);
    res = calc_rank_cd(weights, txt, query, DEF_NORM_METHOD);
 
    PG_FREE_IF_COPY(win, 0);
    PG_FREE_IF_COPY(txt, 1);
    PG_FREE_IF_COPY(query, 2);
    PG_RETURN_FLOAT4(res);
}
 
Datum
ts_rankcd_ttf(PG_FUNCTION_ARGS)
{
    TSVector    txt = PG_GETARG_TSVECTOR(0);
    TSQuery     query = PG_GETARG_TSQUERY(1);
    int         method = PG_GETARG_INT32(2);
    float       res;
 
    res = calc_rank_cd(default_weights, txt, query, method);
 
    PG_FREE_IF_COPY(txt, 0);
    PG_FREE_IF_COPY(query, 1);
    PG_RETURN_FLOAT4(res);
}
 
Datum
ts_rankcd_tt(PG_FUNCTION_ARGS)
{
    TSVector    txt = PG_GETARG_TSVECTOR(0);
    TSQuery     query = PG_GETARG_TSQUERY(1);
    float       res;
 
    res = calc_rank_cd(default_weights, txt, query, DEF_NORM_METHOD);
 
    PG_FREE_IF_COPY(txt, 0);
    PG_FREE_IF_COPY(query, 1);
    PG_RETURN_FLOAT4(res);
}