tsquery.c

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/*-------------------------------------------------------------------------
 *
 * tsquery.c
 *    I/O functions for tsquery
 *
 * Portions Copyright (c) 1996-2020, PostgreSQL Global Development Group
 *
 *
 * IDENTIFICATION
 *    src/backend/utils/adt/tsquery.c
 *
 *-------------------------------------------------------------------------
 */

#include "postgres.h"

#include "libpq/pqformat.h"
#include "miscadmin.h"
#include "tsearch/ts_locale.h"
#include "tsearch/ts_type.h"
#include "tsearch/ts_utils.h"
#include "utils/builtins.h"
#include "utils/memutils.h"
#include "utils/pg_crc.h"

/* FTS operator priorities, see ts_type.h */
const int   tsearch_op_priority[OP_COUNT] =
{
    4,                          /* OP_NOT */
    2,                          /* OP_AND */
    1,                          /* OP_OR */
    3                           /* OP_PHRASE */
};

/*
 * parser's states
 */
typedef enum
{
    WAITOPERAND = 1,
    WAITOPERATOR = 2,
    WAITFIRSTOPERAND = 3
} ts_parserstate;

/*
 * token types for parsing
 */
typedef enum
{
    PT_END = 0,
    PT_ERR = 1,
    PT_VAL = 2,
    PT_OPR = 3,
    PT_OPEN = 4,
    PT_CLOSE = 5
} ts_tokentype;

/*
 * get token from query string
 *
 * *operator is filled in with OP_* when return values is PT_OPR,
 * but *weight could contain a distance value in case of phrase operator.
 * *strval, *lenval and *weight are filled in when return value is PT_VAL
 *
 */
typedef ts_tokentype (*ts_tokenizer) (TSQueryParserState state, int8 *operator,
                                      int *lenval, char **strval,
                                      int16 *weight, bool *prefix);

struct TSQueryParserStateData
{
    /* Tokenizer used for parsing tsquery */
    ts_tokenizer gettoken;

    /* State of tokenizer function */
    char       *buffer;         /* entire string we are scanning */
    char       *buf;            /* current scan point */
    int         count;          /* nesting count, incremented by (,
                                 * decremented by ) */
    bool        in_quotes;      /* phrase in quotes "" */
    ts_parserstate state;

    /* polish (prefix) notation in list, filled in by push* functions */
    List       *polstr;

    /*
     * Strings from operands are collected in op. curop is a pointer to the
     * end of used space of op.
     */
    char       *op;
    char       *curop;
    int         lenop;          /* allocated size of op */
    int         sumlen;         /* used size of op */

    /* state for value's parser */
    TSVectorParseState valstate;
};

/*
 * subroutine to parse the modifiers (weight and prefix flag currently)
 * part, like ':AB*' of a query.
 */
static char *
get_modifiers(char *buf, int16 *weight, bool *prefix)
{
    *weight = 0;
    *prefix = false;

    if (!t_iseq(buf, ':'))
        return buf;

    buf++;
    while (*buf && pg_mblen(buf) == 1)
    {
        switch (*buf)
        {
            case 'a':
            case 'A':
                *weight |= 1 << 3;
                break;
            case 'b':
            case 'B':
                *weight |= 1 << 2;
                break;
            case 'c':
            case 'C':
                *weight |= 1 << 1;
                break;
            case 'd':
            case 'D':
                *weight |= 1;
                break;
            case '*':
                *prefix = true;
                break;
            default:
                return buf;
        }
        buf++;
    }

    return buf;
}

/*
 * Parse phrase operator. The operator
 * may take the following forms:
 *
 *      a <N> b (distance is exactly N lexemes)
 *      a <-> b (default distance = 1)
 *
 * The buffer should begin with '<' char
 */
static bool
parse_phrase_operator(TSQueryParserState pstate, int16 *distance)
{
    enum
    {
        PHRASE_OPEN = 0,
        PHRASE_DIST,
        PHRASE_CLOSE,
        PHRASE_FINISH
    }           state = PHRASE_OPEN;
    char       *ptr = pstate->buf;
    char       *endptr;
    long        l = 1;          /* default distance */

    while (*ptr)
    {
        switch (state)
        {
            case PHRASE_OPEN:
                if (t_iseq(ptr, '<'))
                {
                    state = PHRASE_DIST;
                    ptr++;
                }
                else
                    return false;
                break;

            case PHRASE_DIST:
                if (t_iseq(ptr, '-'))
                {
                    state = PHRASE_CLOSE;
                    ptr++;
                    continue;
                }

                if (!t_isdigit(ptr))
                    return false;

                errno = 0;
                l = strtol(ptr, &endptr, 10);
                if (ptr == endptr)
                    return false;
                else if (errno == ERANGE || l < 0 || l > MAXENTRYPOS)
                    ereport(ERROR,
                            (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                             errmsg("distance in phrase operator should not be greater than %d",
                                    MAXENTRYPOS)));
                else
                {
                    state = PHRASE_CLOSE;
                    ptr = endptr;
                }
                break;

            case PHRASE_CLOSE:
                if (t_iseq(ptr, '>'))
                {
                    state = PHRASE_FINISH;
                    ptr++;
                }
                else
                    return false;
                break;

            case PHRASE_FINISH:
                *distance = (int16) l;
                pstate->buf = ptr;
                return true;
        }
    }

    return false;
}

/*
 * Parse OR operator used in websearch_to_tsquery(), returns true if we
 * believe that "OR" literal could be an operator OR
 */
static bool
parse_or_operator(TSQueryParserState pstate)
{
    char       *ptr = pstate->buf;

    if (pstate->in_quotes)
        return false;

    /* it should begin with "OR" literal */
    if (pg_strncasecmp(ptr, "or", 2) != 0)
        return false;

    ptr += 2;

    /*
     * it shouldn't be a part of any word but somewhere later it should be
     * some operand
     */
    if (*ptr == '\0')           /* no operand */
        return false;

    /* it shouldn't be a part of any word */
    if (t_iseq(ptr, '-') || t_iseq(ptr, '_') || t_isalpha(ptr) || t_isdigit(ptr))
        return false;

    for (;;)
    {
        ptr += pg_mblen(ptr);

        if (*ptr == '\0')       /* got end of string without operand */
            return false;

        /*
         * Suppose, we found an operand, but could be a not correct operand.
         * So we still treat OR literal as operation with possibly incorrect
         * operand and  will not search it as lexeme
         */
        if (!t_isspace(ptr))
            break;
    }

    pstate->buf += 2;
    return true;
}

static ts_tokentype
gettoken_query_standard(TSQueryParserState state, int8 *operator,
                        int *lenval, char **strval,
                        int16 *weight, bool *prefix)
{
    *weight = 0;
    *prefix = false;

    while (true)
    {
        switch (state->state)
        {
            case WAITFIRSTOPERAND:
            case WAITOPERAND:
                if (t_iseq(state->buf, '!'))
                {
                    state->buf++;
                    state->state = WAITOPERAND;
                    *operator = OP_NOT;
                    return PT_OPR;
                }
                else if (t_iseq(state->buf, '('))
                {
                    state->buf++;
                    state->state = WAITOPERAND;
                    state->count++;
                    return PT_OPEN;
                }
                else if (t_iseq(state->buf, ':'))
                {
                    ereport(ERROR,
                            (errcode(ERRCODE_SYNTAX_ERROR),
                             errmsg("syntax error in tsquery: \"%s\"",
                                    state->buffer)));
                }
                else if (!t_isspace(state->buf))
                {
                    /*
                     * We rely on the tsvector parser to parse the value for
                     * us
                     */
                    reset_tsvector_parser(state->valstate, state->buf);
                    if (gettoken_tsvector(state->valstate, strval, lenval,
                                          NULL, NULL, &state->buf))
                    {
                        state->buf = get_modifiers(state->buf, weight, prefix);
                        state->state = WAITOPERATOR;
                        return PT_VAL;
                    }
                    else if (state->state == WAITFIRSTOPERAND)
                    {
                        return PT_END;
                    }
                    else
                        ereport(ERROR,
                                (errcode(ERRCODE_SYNTAX_ERROR),
                                 errmsg("no operand in tsquery: \"%s\"",
                                        state->buffer)));
                }
                break;

            case WAITOPERATOR:
                if (t_iseq(state->buf, '&'))
                {
                    state->buf++;
                    state->state = WAITOPERAND;
                    *operator = OP_AND;
                    return PT_OPR;
                }
                else if (t_iseq(state->buf, '|'))
                {
                    state->buf++;
                    state->state = WAITOPERAND;
                    *operator = OP_OR;
                    return PT_OPR;
                }
                else if (parse_phrase_operator(state, weight))
                {
                    /* weight var is used as storage for distance */
                    state->state = WAITOPERAND;
                    *operator = OP_PHRASE;
                    return PT_OPR;
                }
                else if (t_iseq(state->buf, ')'))
                {
                    state->buf++;
                    state->count--;
                    return (state->count < 0) ? PT_ERR : PT_CLOSE;
                }
                else if (*state->buf == '\0')
                {
                    return (state->count) ? PT_ERR : PT_END;
                }
                else if (!t_isspace(state->buf))
                {
                    return PT_ERR;
                }
                break;
        }

        state->buf += pg_mblen(state->buf);
    }
}

static ts_tokentype
gettoken_query_websearch(TSQueryParserState state, int8 *operator,
                         int *lenval, char **strval,
                         int16 *weight, bool *prefix)
{
    *weight = 0;
    *prefix = false;

    while (true)
    {
        switch (state->state)
        {
            case WAITFIRSTOPERAND:
            case WAITOPERAND:
                if (t_iseq(state->buf, '-'))
                {
                    state->buf++;
                    state->state = WAITOPERAND;

                    if (state->in_quotes)
                        continue;

                    *operator = OP_NOT;
                    return PT_OPR;
                }
                else if (t_iseq(state->buf, '"'))
                {
                    state->buf++;

                    if (!state->in_quotes)
                    {
                        state->state = WAITOPERAND;

                        if (strchr(state->buf, '"'))
                        {
                            /* quoted text should be ordered <-> */
                            state->in_quotes = true;
                            return PT_OPEN;
                        }

                        /* web search tolerates missing quotes */
                        continue;
                    }
                    else
                    {
                        /* we have to provide an operand */
                        state->in_quotes = false;
                        state->state = WAITOPERATOR;
                        pushStop(state);
                        return PT_CLOSE;
                    }
                }
                else if (ISOPERATOR(state->buf))
                {
                    /* or else gettoken_tsvector() will raise an error */
                    state->buf++;
                    state->state = WAITOPERAND;
                    continue;
                }
                else if (!t_isspace(state->buf))
                {
                    /*
                     * We rely on the tsvector parser to parse the value for
                     * us
                     */
                    reset_tsvector_parser(state->valstate, state->buf);
                    if (gettoken_tsvector(state->valstate, strval, lenval,
                                          NULL, NULL, &state->buf))
                    {
                        state->state = WAITOPERATOR;
                        return PT_VAL;
                    }
                    else if (state->state == WAITFIRSTOPERAND)
                    {
                        return PT_END;
                    }
                    else
                    {
                        /* finally, we have to provide an operand */
                        pushStop(state);
                        return PT_END;
                    }
                }
                break;

            case WAITOPERATOR:
                if (t_iseq(state->buf, '"'))
                {
                    if (!state->in_quotes)
                    {
                        /*
                         * put implicit AND after an operand and handle this
                         * quote in WAITOPERAND
                         */
                        state->state = WAITOPERAND;
                        *operator = OP_AND;
                        return PT_OPR;
                    }
                    else
                    {
                        state->buf++;

                        /* just close quotes */
                        state->in_quotes = false;
                        return PT_CLOSE;
                    }
                }
                else if (parse_or_operator(state))
                {
                    state->state = WAITOPERAND;
                    *operator = OP_OR;
                    return PT_OPR;
                }
                else if (*state->buf == '\0')
                {
                    return PT_END;
                }
                else if (!t_isspace(state->buf))
                {
                    if (state->in_quotes)
                    {
                        /* put implicit <-> after an operand */
                        *operator = OP_PHRASE;
                        *weight = 1;
                    }
                    else
                    {
                        /* put implicit AND after an operand */
                        *operator = OP_AND;
                    }

                    state->state = WAITOPERAND;
                    return PT_OPR;
                }
                break;
        }

        state->buf += pg_mblen(state->buf);
    }
}

static ts_tokentype
gettoken_query_plain(TSQueryParserState state, int8 *operator,
                     int *lenval, char **strval,
                     int16 *weight, bool *prefix)
{
    *weight = 0;
    *prefix = false;

    if (*state->buf == '\0')
        return PT_END;

    *strval = state->buf;
    *lenval = strlen(state->buf);
    state->buf += *lenval;
    state->count++;
    return PT_VAL;
}

/*
 * Push an operator to state->polstr
 */
void
pushOperator(TSQueryParserState state, int8 oper, int16 distance)
{
    QueryOperator *tmp;

    Assert(oper == OP_NOT || oper == OP_AND || oper == OP_OR || oper == OP_PHRASE);

    tmp = (QueryOperator *) palloc0(sizeof(QueryOperator));
    tmp->type = QI_OPR;
    tmp->oper = oper;
    tmp->distance = (oper == OP_PHRASE) ? distance : 0;
    /* left is filled in later with findoprnd */

    state->polstr = lcons(tmp, state->polstr);
}

static void
pushValue_internal(TSQueryParserState state, pg_crc32 valcrc, int distance, int lenval, int weight, bool prefix)
{
    QueryOperand *tmp;

    if (distance >= MAXSTRPOS)
        ereport(ERROR,
                (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
                 errmsg("value is too big in tsquery: \"%s\"",
                        state->buffer)));
    if (lenval >= MAXSTRLEN)
        ereport(ERROR,
                (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
                 errmsg("operand is too long in tsquery: \"%s\"",
                        state->buffer)));

    tmp = (QueryOperand *) palloc0(sizeof(QueryOperand));
    tmp->type = QI_VAL;
    tmp->weight = weight;
    tmp->prefix = prefix;
    tmp->valcrc = (int32) valcrc;
    tmp->length = lenval;
    tmp->distance = distance;

    state->polstr = lcons(tmp, state->polstr);
}

/*
 * Push an operand to state->polstr.
 *
 * strval must point to a string equal to state->curop. lenval is the length
 * of the string.
 */
void
pushValue(TSQueryParserState state, char *strval, int lenval, int16 weight, bool prefix)
{
    pg_crc32    valcrc;

    if (lenval >= MAXSTRLEN)
        ereport(ERROR,
                (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
                 errmsg("word is too long in tsquery: \"%s\"",
                        state->buffer)));

    INIT_LEGACY_CRC32(valcrc);
    COMP_LEGACY_CRC32(valcrc, strval, lenval);
    FIN_LEGACY_CRC32(valcrc);
    pushValue_internal(state, valcrc, state->curop - state->op, lenval, weight, prefix);

    /* append the value string to state.op, enlarging buffer if needed first */
    while (state->curop - state->op + lenval + 1 >= state->lenop)
    {
        int         used = state->curop - state->op;

        state->lenop *= 2;
        state->op = (char *) repalloc((void *) state->op, state->lenop);
        state->curop = state->op + used;
    }
    memcpy((void *) state->curop, (void *) strval, lenval);
    state->curop += lenval;
    *(state->curop) = '\0';
    state->curop++;
    state->sumlen += lenval + 1 /* \0 */ ;
}


/*
 * Push a stopword placeholder to state->polstr
 */
void
pushStop(TSQueryParserState state)
{
    QueryOperand *tmp;

    tmp = (QueryOperand *) palloc0(sizeof(QueryOperand));
    tmp->type = QI_VALSTOP;

    state->polstr = lcons(tmp, state->polstr);
}


#define STACKDEPTH  32

typedef struct OperatorElement
{
    int8        op;
    int16       distance;
} OperatorElement;

static void
pushOpStack(OperatorElement *stack, int *lenstack, int8 op, int16 distance)
{
    if (*lenstack == STACKDEPTH)    /* internal error */
        elog(ERROR, "tsquery stack too small");

    stack[*lenstack].op = op;
    stack[*lenstack].distance = distance;

    (*lenstack)++;
}

static void
cleanOpStack(TSQueryParserState state,
             OperatorElement *stack, int *lenstack, int8 op)
{
    int         opPriority = OP_PRIORITY(op);

    while (*lenstack)
    {
        /* NOT is right associative unlike to others */
        if ((op != OP_NOT && opPriority > OP_PRIORITY(stack[*lenstack - 1].op)) ||
            (op == OP_NOT && opPriority >= OP_PRIORITY(stack[*lenstack - 1].op)))
            break;

        (*lenstack)--;
        pushOperator(state, stack[*lenstack].op,
                     stack[*lenstack].distance);
    }
}

/*
 * Make polish (prefix) notation of query.
 *
 * See parse_tsquery for explanation of pushval.
 */
static void
makepol(TSQueryParserState state,
        PushFunction pushval,
        Datum opaque)
{
    int8        operator = 0;
    ts_tokentype type;
    int         lenval = 0;
    char       *strval = NULL;
    OperatorElement opstack[STACKDEPTH];
    int         lenstack = 0;
    int16       weight = 0;
    bool        prefix;

    /* since this function recurses, it could be driven to stack overflow */
    check_stack_depth();

    while ((type = state->gettoken(state, &operator,
                                   &lenval, &strval,
                                   &weight, &prefix)) != PT_END)
    {
        switch (type)
        {
            case PT_VAL:
                pushval(opaque, state, strval, lenval, weight, prefix);
                break;
            case PT_OPR:
                cleanOpStack(state, opstack, &lenstack, operator);
                pushOpStack(opstack, &lenstack, operator, weight);
                break;
            case PT_OPEN:
                makepol(state, pushval, opaque);
                break;
            case PT_CLOSE:
                cleanOpStack(state, opstack, &lenstack, OP_OR /* lowest */ );
                return;
            case PT_ERR:
            default:
                ereport(ERROR,
                        (errcode(ERRCODE_SYNTAX_ERROR),
                         errmsg("syntax error in tsquery: \"%s\"",
                                state->buffer)));
        }
    }

    cleanOpStack(state, opstack, &lenstack, OP_OR /* lowest */ );
}

static void
findoprnd_recurse(QueryItem *ptr, uint32 *pos, int nnodes, bool *needcleanup)
{
    /* since this function recurses, it could be driven to stack overflow. */
    check_stack_depth();

    if (*pos >= nnodes)
        elog(ERROR, "malformed tsquery: operand not found");

    if (ptr[*pos].type == QI_VAL)
    {
        (*pos)++;
    }
    else if (ptr[*pos].type == QI_VALSTOP)
    {
        *needcleanup = true;    /* we'll have to remove stop words */
        (*pos)++;
    }
    else
    {
        Assert(ptr[*pos].type == QI_OPR);

        if (ptr[*pos].qoperator.oper == OP_NOT)
        {
            ptr[*pos].qoperator.left = 1;   /* fixed offset */
            (*pos)++;

            /* process the only argument */
            findoprnd_recurse(ptr, pos, nnodes, needcleanup);
        }
        else
        {
            QueryOperator *curitem = &ptr[*pos].qoperator;
            int         tmp = *pos; /* save current position */

            Assert(curitem->oper == OP_AND ||
                   curitem->oper == OP_OR ||
                   curitem->oper == OP_PHRASE);

            (*pos)++;

            /* process RIGHT argument */
            findoprnd_recurse(ptr, pos, nnodes, needcleanup);

            curitem->left = *pos - tmp; /* set LEFT arg's offset */

            /* process LEFT argument */
            findoprnd_recurse(ptr, pos, nnodes, needcleanup);
        }
    }
}


/*
 * Fill in the left-fields previously left unfilled.
 * The input QueryItems must be in polish (prefix) notation.
 * Also, set *needcleanup to true if there are any QI_VALSTOP nodes.
 */
static void
findoprnd(QueryItem *ptr, int size, bool *needcleanup)
{
    uint32      pos;

    *needcleanup = false;
    pos = 0;
    findoprnd_recurse(ptr, &pos, size, needcleanup);

    if (pos != size)
        elog(ERROR, "malformed tsquery: extra nodes");
}


/*
 * Each value (operand) in the query is passed to pushval. pushval can
 * transform the simple value to an arbitrarily complex expression using
 * pushValue and pushOperator. It must push a single value with pushValue,
 * a complete expression with all operands, or a stopword placeholder
 * with pushStop, otherwise the prefix notation representation will be broken,
 * having an operator with no operand.
 *
 * opaque is passed on to pushval as is, pushval can use it to store its
 * private state.
 */
TSQuery
parse_tsquery(char *buf,
              PushFunction pushval,
              Datum opaque,
              int flags)
{
    struct TSQueryParserStateData state;
    int         i;
    TSQuery     query;
    int         commonlen;
    QueryItem  *ptr;
    ListCell   *cell;
    bool        needcleanup;
    int         tsv_flags = P_TSV_OPR_IS_DELIM | P_TSV_IS_TSQUERY;

    /* plain should not be used with web */
    Assert((flags & (P_TSQ_PLAIN | P_TSQ_WEB)) != (P_TSQ_PLAIN | P_TSQ_WEB));

    /* select suitable tokenizer */
    if (flags & P_TSQ_PLAIN)
        state.gettoken = gettoken_query_plain;
    else if (flags & P_TSQ_WEB)
    {
        state.gettoken = gettoken_query_websearch;
        tsv_flags |= P_TSV_IS_WEB;
    }
    else
        state.gettoken = gettoken_query_standard;

    /* init state */
    state.buffer = buf;
    state.buf = buf;
    state.count = 0;
    state.in_quotes = false;
    state.state = WAITFIRSTOPERAND;
    state.polstr = NIL;

    /* init value parser's state */
    state.valstate = init_tsvector_parser(state.buffer, tsv_flags);

    /* init list of operand */
    state.sumlen = 0;
    state.lenop = 64;
    state.curop = state.op = (char *) palloc(state.lenop);
    *(state.curop) = '\0';

    /* parse query & make polish notation (postfix, but in reverse order) */
    makepol(&state, pushval, opaque);

    close_tsvector_parser(state.valstate);

    if (list_length(state.polstr) == 0)
    {
        ereport(NOTICE,
                (errmsg("text-search query doesn't contain lexemes: \"%s\"",
                        state.buffer)));
        query = (TSQuery) palloc(HDRSIZETQ);
        SET_VARSIZE(query, HDRSIZETQ);
        query->size = 0;
        return query;
    }

    if (TSQUERY_TOO_BIG(list_length(state.polstr), state.sumlen))
        ereport(ERROR,
                (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
                 errmsg("tsquery is too large")));
    commonlen = COMPUTESIZE(list_length(state.polstr), state.sumlen);

    /* Pack the QueryItems in the final TSQuery struct to return to caller */
    query = (TSQuery) palloc0(commonlen);
    SET_VARSIZE(query, commonlen);
    query->size = list_length(state.polstr);
    ptr = GETQUERY(query);

    /* Copy QueryItems to TSQuery */
    i = 0;
    foreach(cell, state.polstr)
    {
        QueryItem  *item = (QueryItem *) lfirst(cell);

        switch (item->type)
        {
            case QI_VAL:
                memcpy(&ptr[i], item, sizeof(QueryOperand));
                break;
            case QI_VALSTOP:
                ptr[i].type = QI_VALSTOP;
                break;
            case QI_OPR:
                memcpy(&ptr[i], item, sizeof(QueryOperator));
                break;
            default:
                elog(ERROR, "unrecognized QueryItem type: %d", item->type);
        }
        i++;
    }

    /* Copy all the operand strings to TSQuery */
    memcpy((void *) GETOPERAND(query), (void *) state.op, state.sumlen);
    pfree(state.op);

    /*
     * Set left operand pointers for every operator.  While we're at it,
     * detect whether there are any QI_VALSTOP nodes.
     */
    findoprnd(ptr, query->size, &needcleanup);

    /*
     * If there are QI_VALSTOP nodes, delete them and simplify the tree.
     */
    if (needcleanup)
        query = cleanup_tsquery_stopwords(query);

    return query;
}

static void
pushval_asis(Datum opaque, TSQueryParserState state, char *strval, int lenval,
             int16 weight, bool prefix)
{
    pushValue(state, strval, lenval, weight, prefix);
}

/*
 * in without morphology
 */
Datum
tsqueryin(PG_FUNCTION_ARGS)
{
    char       *in = PG_GETARG_CSTRING(0);

    PG_RETURN_TSQUERY(parse_tsquery(in, pushval_asis, PointerGetDatum(NULL), 0));
}

/*
 * out function
 */
typedef struct
{
    QueryItem  *curpol;
    char       *buf;
    char       *cur;
    char       *op;
    int         buflen;
} INFIX;

/* Makes sure inf->buf is large enough for adding 'addsize' bytes */
#define RESIZEBUF(inf, addsize) \
while( ( (inf)->cur - (inf)->buf ) + (addsize) + 1 >= (inf)->buflen ) \
{ \
    int len = (inf)->cur - (inf)->buf; \
    (inf)->buflen *= 2; \
    (inf)->buf = (char*) repalloc( (void*)(inf)->buf, (inf)->buflen ); \
    (inf)->cur = (inf)->buf + len; \
}

/*
 * recursively traverse the tree and
 * print it in infix (human-readable) form
 */
static void
infix(INFIX *in, int parentPriority, bool rightPhraseOp)
{
    /* since this function recurses, it could be driven to stack overflow. */
    check_stack_depth();

    if (in->curpol->type == QI_VAL)
    {
        QueryOperand *curpol = &in->curpol->qoperand;
        char       *op = in->op + curpol->distance;
        int         clen;

        RESIZEBUF(in, curpol->length * (pg_database_encoding_max_length() + 1) + 2 + 6);
        *(in->cur) = '\'';
        in->cur++;
        while (*op)
        {
            if (t_iseq(op, '\''))
            {
                *(in->cur) = '\'';
                in->cur++;
            }
            else if (t_iseq(op, '\\'))
            {
                *(in->cur) = '\\';
                in->cur++;
            }
            COPYCHAR(in->cur, op);

            clen = pg_mblen(op);
            op += clen;
            in->cur += clen;
        }
        *(in->cur) = '\'';
        in->cur++;
        if (curpol->weight || curpol->prefix)
        {
            *(in->cur) = ':';
            in->cur++;
            if (curpol->prefix)
            {
                *(in->cur) = '*';
                in->cur++;
            }
            if (curpol->weight & (1 << 3))
            {
                *(in->cur) = 'A';
                in->cur++;
            }
            if (curpol->weight & (1 << 2))
            {
                *(in->cur) = 'B';
                in->cur++;
            }
            if (curpol->weight & (1 << 1))
            {
                *(in->cur) = 'C';
                in->cur++;
            }
            if (curpol->weight & 1)
            {
                *(in->cur) = 'D';
                in->cur++;
            }
        }
        *(in->cur) = '\0';
        in->curpol++;
    }
    else if (in->curpol->qoperator.oper == OP_NOT)
    {
        int         priority = QO_PRIORITY(in->curpol);

        if (priority < parentPriority)
        {
            RESIZEBUF(in, 2);
            sprintf(in->cur, "( ");
            in->cur = strchr(in->cur, '\0');
        }
        RESIZEBUF(in, 1);
        *(in->cur) = '!';
        in->cur++;
        *(in->cur) = '\0';
        in->curpol++;

        infix(in, priority, false);
        if (priority < parentPriority)
        {
            RESIZEBUF(in, 2);
            sprintf(in->cur, " )");
            in->cur = strchr(in->cur, '\0');
        }
    }
    else
    {
        int8        op = in->curpol->qoperator.oper;
        int         priority = QO_PRIORITY(in->curpol);
        int16       distance = in->curpol->qoperator.distance;
        INFIX       nrm;
        bool        needParenthesis = false;

        in->curpol++;
        if (priority < parentPriority ||
        /* phrase operator depends on order */
            (op == OP_PHRASE && rightPhraseOp))
        {
            needParenthesis = true;
            RESIZEBUF(in, 2);
            sprintf(in->cur, "( ");
            in->cur = strchr(in->cur, '\0');
        }

        nrm.curpol = in->curpol;
        nrm.op = in->op;
        nrm.buflen = 16;
        nrm.cur = nrm.buf = (char *) palloc(sizeof(char) * nrm.buflen);

        /* get right operand */
        infix(&nrm, priority, (op == OP_PHRASE));

        /* get & print left operand */
        in->curpol = nrm.curpol;
        infix(in, priority, false);

        /* print operator & right operand */
        RESIZEBUF(in, 3 + (2 + 10 /* distance */ ) + (nrm.cur - nrm.buf));
        switch (op)
        {
            case OP_OR:
                sprintf(in->cur, " | %s", nrm.buf);
                break;
            case OP_AND:
                sprintf(in->cur, " & %s", nrm.buf);
                break;
            case OP_PHRASE:
                if (distance != 1)
                    sprintf(in->cur, " <%d> %s", distance, nrm.buf);
                else
                    sprintf(in->cur, " <-> %s", nrm.buf);
                break;
            default:
                /* OP_NOT is handled in above if-branch */
                elog(ERROR, "unrecognized operator type: %d", op);
        }
        in->cur = strchr(in->cur, '\0');
        pfree(nrm.buf);

        if (needParenthesis)
        {
            RESIZEBUF(in, 2);
            sprintf(in->cur, " )");
            in->cur = strchr(in->cur, '\0');
        }
    }
}

Datum
tsqueryout(PG_FUNCTION_ARGS)
{
    TSQuery     query = PG_GETARG_TSQUERY(0);
    INFIX       nrm;

    if (query->size == 0)
    {
        char       *b = palloc(1);

        *b = '\0';
        PG_RETURN_POINTER(b);
    }
    nrm.curpol = GETQUERY(query);
    nrm.buflen = 32;
    nrm.cur = nrm.buf = (char *) palloc(sizeof(char) * nrm.buflen);
    *(nrm.cur) = '\0';
    nrm.op = GETOPERAND(query);
    infix(&nrm, -1 /* lowest priority */ , false);

    PG_FREE_IF_COPY(query, 0);
    PG_RETURN_CSTRING(nrm.buf);
}

/*
 * Binary Input / Output functions. The binary format is as follows:
 *
 * uint32    number of operators/operands in the query
 *
 * Followed by the operators and operands, in prefix notation. For each
 * operand:
 *
 * uint8    type, QI_VAL
 * uint8    weight
 *          operand text in client encoding, null-terminated
 * uint8    prefix
 *
 * For each operator:
 * uint8    type, QI_OPR
 * uint8    operator, one of OP_AND, OP_PHRASE OP_OR, OP_NOT.
 * uint16   distance (only for OP_PHRASE)
 */
Datum
tsquerysend(PG_FUNCTION_ARGS)
{
    TSQuery     query = PG_GETARG_TSQUERY(0);
    StringInfoData buf;
    int         i;
    QueryItem  *item = GETQUERY(query);

    pq_begintypsend(&buf);

    pq_sendint32(&buf, query->size);
    for (i = 0; i < query->size; i++)
    {
        pq_sendint8(&buf, item->type);

        switch (item->type)
        {
            case QI_VAL:
                pq_sendint8(&buf, item->qoperand.weight);
                pq_sendint8(&buf, item->qoperand.prefix);
                pq_sendstring(&buf, GETOPERAND(query) + item->qoperand.distance);
                break;
            case QI_OPR:
                pq_sendint8(&buf, item->qoperator.oper);
                if (item->qoperator.oper == OP_PHRASE)
                    pq_sendint16(&buf, item->qoperator.distance);
                break;
            default:
                elog(ERROR, "unrecognized tsquery node type: %d", item->type);
        }
        item++;
    }

    PG_FREE_IF_COPY(query, 0);

    PG_RETURN_BYTEA_P(pq_endtypsend(&buf));
}

Datum
tsqueryrecv(PG_FUNCTION_ARGS)
{
    StringInfo  buf = (StringInfo) PG_GETARG_POINTER(0);
    TSQuery     query;
    int         i,
                len;
    QueryItem  *item;
    int         datalen;
    char       *ptr;
    uint32      size;
    const char **operands;
    bool        needcleanup;

    size = pq_getmsgint(buf, sizeof(uint32));
    if (size > (MaxAllocSize / sizeof(QueryItem)))
        elog(ERROR, "invalid size of tsquery");

    /* Allocate space to temporarily hold operand strings */
    operands = palloc(size * sizeof(char *));

    /* Allocate space for all the QueryItems. */
    len = HDRSIZETQ + sizeof(QueryItem) * size;
    query = (TSQuery) palloc0(len);
    query->size = size;
    item = GETQUERY(query);

    datalen = 0;
    for (i = 0; i < size; i++)
    {
        item->type = (int8) pq_getmsgint(buf, sizeof(int8));

        if (item->type == QI_VAL)
        {
            size_t      val_len;    /* length after recoding to server
                                     * encoding */
            uint8       weight;
            uint8       prefix;
            const char *val;
            pg_crc32    valcrc;

            weight = (uint8) pq_getmsgint(buf, sizeof(uint8));
            prefix = (uint8) pq_getmsgint(buf, sizeof(uint8));
            val = pq_getmsgstring(buf);
            val_len = strlen(val);

            /* Sanity checks */

            if (weight > 0xF)
                elog(ERROR, "invalid tsquery: invalid weight bitmap");

            if (val_len > MAXSTRLEN)
                elog(ERROR, "invalid tsquery: operand too long");

            if (datalen > MAXSTRPOS)
                elog(ERROR, "invalid tsquery: total operand length exceeded");

            /* Looks valid. */

            INIT_LEGACY_CRC32(valcrc);
            COMP_LEGACY_CRC32(valcrc, val, val_len);
            FIN_LEGACY_CRC32(valcrc);

            item->qoperand.weight = weight;
            item->qoperand.prefix = (prefix) ? true : false;
            item->qoperand.valcrc = (int32) valcrc;
            item->qoperand.length = val_len;
            item->qoperand.distance = datalen;

            /*
             * Operand strings are copied to the final struct after this loop;
             * here we just collect them to an array
             */
            operands[i] = val;

            datalen += val_len + 1; /* + 1 for the '\0' terminator */
        }
        else if (item->type == QI_OPR)
        {
            int8        oper;

            oper = (int8) pq_getmsgint(buf, sizeof(int8));
            if (oper != OP_NOT && oper != OP_OR && oper != OP_AND && oper != OP_PHRASE)
                elog(ERROR, "invalid tsquery: unrecognized operator type %d",
                     (int) oper);
            if (i == size - 1)
                elog(ERROR, "invalid pointer to right operand");

            item->qoperator.oper = oper;
            if (oper == OP_PHRASE)
                item->qoperator.distance = (int16) pq_getmsgint(buf, sizeof(int16));
        }
        else
            elog(ERROR, "unrecognized tsquery node type: %d", item->type);

        item++;
    }

    /* Enlarge buffer to make room for the operand values. */
    query = (TSQuery) repalloc(query, len + datalen);
    item = GETQUERY(query);
    ptr = GETOPERAND(query);

    /*
     * Fill in the left-pointers. Checks that the tree is well-formed as a
     * side-effect.
     */
    findoprnd(item, size, &needcleanup);

    /* Can't have found any QI_VALSTOP nodes */
    Assert(!needcleanup);

    /* Copy operands to output struct */
    for (i = 0; i < size; i++)
    {
        if (item->type == QI_VAL)
        {
            memcpy(ptr, operands[i], item->qoperand.length + 1);
            ptr += item->qoperand.length + 1;
        }
        item++;
    }

    pfree(operands);

    Assert(ptr - GETOPERAND(query) == datalen);

    SET_VARSIZE(query, len + datalen);

    PG_RETURN_TSQUERY(query);
}

/*
 * debug function, used only for view query
 * which will be executed in non-leaf pages in index
 */
Datum
tsquerytree(PG_FUNCTION_ARGS)
{
    TSQuery     query = PG_GETARG_TSQUERY(0);
    INFIX       nrm;
    text       *res;
    QueryItem  *q;
    int         len;

    if (query->size == 0)
    {
        res = (text *) palloc(VARHDRSZ);
        SET_VARSIZE(res, VARHDRSZ);
        PG_RETURN_POINTER(res);
    }

    q = clean_NOT(GETQUERY(query), &len);

    if (!q)
    {
        res = cstring_to_text("T");
    }
    else
    {
        nrm.curpol = q;
        nrm.buflen = 32;
        nrm.cur = nrm.buf = (char *) palloc(sizeof(char) * nrm.buflen);
        *(nrm.cur) = '\0';
        nrm.op = GETOPERAND(query);
        infix(&nrm, -1, false);
        res = cstring_to_text_with_len(nrm.buf, nrm.cur - nrm.buf);
        pfree(q);
    }

    PG_FREE_IF_COPY(query, 0);

    PG_RETURN_TEXT_P(res);
}