tsquery_cleanup.c

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/*-------------------------------------------------------------------------
 *
 * tsquery_cleanup.c
 *   Cleanup query from NOT values and/or stopword
 *   Utility functions to correct work.
 *
 * Portions Copyright (c) 1996-2013, PostgreSQL Global Development Group
 *
 *
 * IDENTIFICATION
 *    src/backend/utils/adt/tsquery_cleanup.c
 *
 *-------------------------------------------------------------------------
 */

#include "postgres.h"

#include "tsearch/ts_utils.h"
#include "miscadmin.h"

typedef struct NODE
{
    struct NODE *left;
    struct NODE *right;
    QueryItem  *valnode;
} NODE;

/*
 * make query tree from plain view of query
 */
static NODE *
maketree(QueryItem *in)
{
    NODE       *node = (NODE *) palloc(sizeof(NODE));

    node->valnode = in;
    node->right = node->left = NULL;
    if (in->type == QI_OPR)
    {
        node->right = maketree(in + 1);
        if (in->qoperator.oper != OP_NOT)
            node->left = maketree(in + in->qoperator.left);
    }
    return node;
}

/*
 * Internal state for plaintree and plainnode
 */
typedef struct
{
    QueryItem  *ptr;
    int         len;            /* allocated size of ptr */
    int         cur;            /* number of elements in ptr */
} PLAINTREE;

static void
plainnode(PLAINTREE *state, NODE *node)
{
    /* since this function recurses, it could be driven to stack overflow. */
    check_stack_depth();

    if (state->cur == state->len)
    {
        state->len *= 2;
        state->ptr = (QueryItem *) repalloc((void *) state->ptr, state->len * sizeof(QueryItem));
    }
    memcpy((void *) &(state->ptr[state->cur]), (void *) node->valnode, sizeof(QueryItem));
    if (node->valnode->type == QI_VAL)
        state->cur++;
    else if (node->valnode->qoperator.oper == OP_NOT)
    {
        state->ptr[state->cur].qoperator.left = 1;
        state->cur++;
        plainnode(state, node->right);
    }
    else
    {
        int         cur = state->cur;

        state->cur++;
        plainnode(state, node->right);
        state->ptr[cur].qoperator.left = state->cur - cur;
        plainnode(state, node->left);
    }
    pfree(node);
}

/*
 * make plain view of tree from a NODE-tree representation
 */
static QueryItem *
plaintree(NODE *root, int *len)
{
    PLAINTREE   pl;

    pl.cur = 0;
    pl.len = 16;
    if (root && (root->valnode->type == QI_VAL || root->valnode->type == QI_OPR))
    {
        pl.ptr = (QueryItem *) palloc(pl.len * sizeof(QueryItem));
        plainnode(&pl, root);
    }
    else
        pl.ptr = NULL;
    *len = pl.cur;
    return pl.ptr;
}

static void
freetree(NODE *node)
{
    /* since this function recurses, it could be driven to stack overflow. */
    check_stack_depth();

    if (!node)
        return;
    if (node->left)
        freetree(node->left);
    if (node->right)
        freetree(node->right);
    pfree(node);
}

/*
 * clean tree for ! operator.
 * It's useful for debug, but in
 * other case, such view is used with search in index.
 * Operator ! always return TRUE
 */
static NODE *
clean_NOT_intree(NODE *node)
{
    /* since this function recurses, it could be driven to stack overflow. */
    check_stack_depth();

    if (node->valnode->type == QI_VAL)
        return node;

    if (node->valnode->qoperator.oper == OP_NOT)
    {
        freetree(node);
        return NULL;
    }

    /* operator & or | */
    if (node->valnode->qoperator.oper == OP_OR)
    {
        if ((node->left = clean_NOT_intree(node->left)) == NULL ||
            (node->right = clean_NOT_intree(node->right)) == NULL)
        {
            freetree(node);
            return NULL;
        }
    }
    else
    {
        NODE       *res = node;

        Assert(node->valnode->qoperator.oper == OP_AND);

        node->left = clean_NOT_intree(node->left);
        node->right = clean_NOT_intree(node->right);
        if (node->left == NULL && node->right == NULL)
        {
            pfree(node);
            res = NULL;
        }
        else if (node->left == NULL)
        {
            res = node->right;
            pfree(node);
        }
        else if (node->right == NULL)
        {
            res = node->left;
            pfree(node);
        }
        return res;
    }
    return node;
}

QueryItem *
clean_NOT(QueryItem *ptr, int *len)
{
    NODE       *root = maketree(ptr);

    return plaintree(clean_NOT_intree(root), len);
}


#ifdef V_UNKNOWN                /* exists in Windows headers */
#undef V_UNKNOWN
#endif
#ifdef V_FALSE                  /* exists in Solaris headers */
#undef V_FALSE
#endif

/*
 * output values for result output parameter of clean_fakeval_intree
 */
#define V_UNKNOWN   0           /* the expression can't be evaluated
                                 * statically */
#define V_TRUE      1           /* the expression is always true (not
                                 * implemented) */
#define V_FALSE     2           /* the expression is always false (not
                                 * implemented) */
#define V_STOP      3           /* the expression is a stop word */

/*
 * Clean query tree from values which is always in
 * text (stopword)
 */
static NODE *
clean_fakeval_intree(NODE *node, char *result)
{
    char        lresult = V_UNKNOWN,
                rresult = V_UNKNOWN;

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

    if (node->valnode->type == QI_VAL)
        return node;
    else if (node->valnode->type == QI_VALSTOP)
    {
        pfree(node);
        *result = V_STOP;
        return NULL;
    }

    Assert(node->valnode->type == QI_OPR);

    if (node->valnode->qoperator.oper == OP_NOT)
    {
        node->right = clean_fakeval_intree(node->right, &rresult);
        if (!node->right)
        {
            *result = V_STOP;
            freetree(node);
            return NULL;
        }
    }
    else
    {
        NODE       *res = node;

        node->left = clean_fakeval_intree(node->left, &lresult);
        node->right = clean_fakeval_intree(node->right, &rresult);

        if (lresult == V_STOP && rresult == V_STOP)
        {
            freetree(node);
            *result = V_STOP;
            return NULL;
        }
        else if (lresult == V_STOP)
        {
            res = node->right;
            pfree(node);
        }
        else if (rresult == V_STOP)
        {
            res = node->left;
            pfree(node);
        }
        return res;
    }
    return node;
}

QueryItem *
clean_fakeval(QueryItem *ptr, int *len)
{
    NODE       *root = maketree(ptr);
    char        result = V_UNKNOWN;
    NODE       *resroot;

    resroot = clean_fakeval_intree(root, &result);
    if (result != V_UNKNOWN)
    {
        ereport(NOTICE,
                (errmsg("text-search query contains only stop words or doesn't contain lexemes, ignored")));
        *len = 0;
        return NULL;
    }

    return plaintree(resroot, len);
}