btree_bit.c

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/*
 * contrib/btree_gist/btree_bit.c
 *
 * Support for bit and varbit types (which act the same for our purposes).
 *
 * Leaf-page keys are bit/varbit values, but internal-page keys are just
 * bytea values containing the first N bytes of the represented bitstring.
 * (In particular, they lack the bit_len field of a bit/varbit Datum.)
 */
#include "postgres.h"
 
#include "btree_gist.h"
#include "btree_utils_var.h"
#include "utils/fmgrprotos.h"
#include "utils/sortsupport.h"
#include "utils/varbit.h"
#include "varatt.h"
 
/* GiST support functions */
PG_FUNCTION_INFO_V1(gbt_bit_compress);
PG_FUNCTION_INFO_V1(gbt_bit_union);
PG_FUNCTION_INFO_V1(gbt_bit_picksplit);
PG_FUNCTION_INFO_V1(gbt_bit_consistent);
PG_FUNCTION_INFO_V1(gbt_bit_penalty);
PG_FUNCTION_INFO_V1(gbt_bit_same);
PG_FUNCTION_INFO_V1(gbt_bit_sortsupport);
PG_FUNCTION_INFO_V1(gbt_varbit_sortsupport);
 
 
/* define for comparison */
 
static bool
gbt_bitgt(const void *a, const void *b, Oid collation, FmgrInfo *flinfo)
{
    return DatumGetBool(DirectFunctionCall2(bitgt,
                                            PointerGetDatum(a),
                                            PointerGetDatum(b)));
}
 
static bool
gbt_bitge(const void *a, const void *b, Oid collation, FmgrInfo *flinfo)
{
    return DatumGetBool(DirectFunctionCall2(bitge,
                                            PointerGetDatum(a),
                                            PointerGetDatum(b)));
}
 
static bool
gbt_biteq(const void *a, const void *b, Oid collation, FmgrInfo *flinfo)
{
    return DatumGetBool(DirectFunctionCall2(biteq,
                                            PointerGetDatum(a),
                                            PointerGetDatum(b)));
}
 
static bool
gbt_bitle(const void *a, const void *b, Oid collation, FmgrInfo *flinfo)
{
    return DatumGetBool(DirectFunctionCall2(bitle,
                                            PointerGetDatum(a),
                                            PointerGetDatum(b)));
}
 
static bool
gbt_bitlt(const void *a, const void *b, Oid collation, FmgrInfo *flinfo)
{
    return DatumGetBool(DirectFunctionCall2(bitlt,
                                            PointerGetDatum(a),
                                            PointerGetDatum(b)));
}
 
/*
 * Notice we use byteacmp here, not bitcmp as you might expect.
 * That's because internal-page keys are bytea.
 */
static int32
gbt_bitcmp(const void *a, const void *b, Oid collation, FmgrInfo *flinfo)
{
    return DatumGetInt32(DirectFunctionCall2(byteacmp,
                                             PointerGetDatum(a),
                                             PointerGetDatum(b)));
}
 
 
/*
 * Convert a leaf-page bit/varbit value to internal-page form.
 *
 * The important change here is to remove the bit_len field so that
 * what we have left looks like a bytea.
 *
 * The business with padding to INTALIGN length appears entirely historical,
 * but we can't remove that without breaking on-disk compatibility.
 * For example, if the lower bound of some leaf page is the 20-bit string
 * of all ones, with data contents FFFFF0, this code pads it to bytea FFFFF000
 * in the internal key representing that page.  If, when we search the index
 * for that value, we did not again pad to FFFFF000, then byteacmp would
 * say that the query is strictly less than the lower bound so we would not
 * descend to that leaf page.
 */
static bytea *
gbt_bit_xfrm(VarBit *leaf)
{
    bytea      *out;
    int         sz = VARBITBYTES(leaf) + VARHDRSZ;
    int         padded_sz = INTALIGN(sz);
 
    out = (bytea *) palloc(padded_sz);
    /* initialize the padding bytes to zero */
    while (sz < padded_sz)
        ((char *) out)[sz++] = 0;
    SET_VARSIZE(out, padded_sz);
    memcpy(VARDATA(out), VARBITS(leaf), VARBITBYTES(leaf));
    return out;
}
 
/*
 * Convert a GBT_VARKEY representation of a leaf key to a palloc'd
 * GBT_VARKEY representation of an internal key.
 * We assume lower == upper since it's a leaf key.
 */
static GBT_VARKEY *
gbt_bit_l2n(GBT_VARKEY *leaf, FmgrInfo *flinfo)
{
    GBT_VARKEY *out;
    GBT_VARKEY_R r = gbt_var_key_readable(leaf);
    bytea      *o;
 
    o = gbt_bit_xfrm((VarBit *) r.lower);
    r.upper = r.lower = o;
    out = gbt_var_key_copy(&r);
    pfree(o);
 
    return out;
}
 
static const gbtree_vinfo tinfo =
{
    gbt_t_bit,
    true,                       /* internal keys can be truncated */
    gbt_bitgt,
    gbt_bitge,
    gbt_biteq,
    gbt_bitle,
    gbt_bitlt,
    gbt_bitcmp,
    gbt_bit_l2n                 /* leaf to internal transformation */
};
 
 
/**************************************************
 * GiST support functions
 **************************************************/
 
Datum
gbt_bit_compress(PG_FUNCTION_ARGS)
{
    GISTENTRY  *entry = (GISTENTRY *) PG_GETARG_POINTER(0);
 
    PG_RETURN_POINTER(gbt_var_compress(entry, &tinfo));
}
 
Datum
gbt_bit_consistent(PG_FUNCTION_ARGS)
{
    GISTENTRY  *entry = (GISTENTRY *) PG_GETARG_POINTER(0);
    VarBit     *query = PG_GETARG_VARBIT_P(1);
    StrategyNumber strategy = (StrategyNumber) PG_GETARG_UINT16(2);
#ifdef NOT_USED
    Oid         subtype = PG_GETARG_OID(3);
#endif
    bool       *recheck = (bool *) PG_GETARG_POINTER(4);
    bool        retval;
    GBT_VARKEY *key = (GBT_VARKEY *) DatumGetPointer(entry->key);
    GBT_VARKEY_R r = gbt_var_key_readable(key);
 
    /* All cases served by this function are exact */
    *recheck = false;
 
    if (GIST_LEAF(entry))
        retval = gbt_var_consistent(&r, query, strategy, PG_GET_COLLATION(),
                                    true, &tinfo, fcinfo->flinfo);
    else
    {
        /* Must convert to internal form to compare to internal-page entries */
        bytea      *q = gbt_bit_xfrm(query);
 
        retval = gbt_var_consistent(&r, q, strategy, PG_GET_COLLATION(),
                                    false, &tinfo, fcinfo->flinfo);
    }
    PG_RETURN_BOOL(retval);
}
 
Datum
gbt_bit_union(PG_FUNCTION_ARGS)
{
    GistEntryVector *entryvec = (GistEntryVector *) PG_GETARG_POINTER(0);
    int32      *size = (int *) PG_GETARG_POINTER(1);
 
    PG_RETURN_POINTER(gbt_var_union(entryvec, size, PG_GET_COLLATION(),
                                    &tinfo, fcinfo->flinfo));
}
 
Datum
gbt_bit_picksplit(PG_FUNCTION_ARGS)
{
    GistEntryVector *entryvec = (GistEntryVector *) PG_GETARG_POINTER(0);
    GIST_SPLITVEC *v = (GIST_SPLITVEC *) PG_GETARG_POINTER(1);
 
    gbt_var_picksplit(entryvec, v, PG_GET_COLLATION(),
                      &tinfo, fcinfo->flinfo);
    PG_RETURN_POINTER(v);
}
 
Datum
gbt_bit_same(PG_FUNCTION_ARGS)
{
    Datum       d1 = PG_GETARG_DATUM(0);
    Datum       d2 = PG_GETARG_DATUM(1);
    bool       *result = (bool *) PG_GETARG_POINTER(2);
 
    *result = gbt_var_same(d1, d2, PG_GET_COLLATION(), &tinfo, fcinfo->flinfo);
    PG_RETURN_POINTER(result);
}
 
Datum
gbt_bit_penalty(PG_FUNCTION_ARGS)
{
    GISTENTRY  *o = (GISTENTRY *) PG_GETARG_POINTER(0);
    GISTENTRY  *n = (GISTENTRY *) PG_GETARG_POINTER(1);
    float      *result = (float *) PG_GETARG_POINTER(2);
 
    PG_RETURN_POINTER(gbt_var_penalty(result, o, n, PG_GET_COLLATION(),
                                      &tinfo, fcinfo->flinfo));
}
 
static int
gbt_bit_ssup_cmp(Datum x, Datum y, SortSupport ssup)
{
    GBT_VARKEY *key1 = PG_DETOAST_DATUM(x);
    GBT_VARKEY *key2 = PG_DETOAST_DATUM(y);
 
    GBT_VARKEY_R arg1 = gbt_var_key_readable(key1);
    GBT_VARKEY_R arg2 = gbt_var_key_readable(key2);
    Datum       result;
 
    /* for leaf items we expect lower == upper, so only compare lower */
    result = DirectFunctionCall2(bitcmp,
                                 PointerGetDatum(arg1.lower),
                                 PointerGetDatum(arg2.lower));
 
    GBT_FREE_IF_COPY(key1, x);
    GBT_FREE_IF_COPY(key2, y);
 
    return DatumGetInt32(result);
}
 
Datum
gbt_bit_sortsupport(PG_FUNCTION_ARGS)
{
    SortSupport ssup = (SortSupport) PG_GETARG_POINTER(0);
 
    ssup->comparator = gbt_bit_ssup_cmp;
    ssup->ssup_extra = NULL;
 
    PG_RETURN_VOID();
}
 
Datum
gbt_varbit_sortsupport(PG_FUNCTION_ARGS)
{
    SortSupport ssup = (SortSupport) PG_GETARG_POINTER(0);
 
    ssup->comparator = gbt_bit_ssup_cmp;
    ssup->ssup_extra = NULL;
 
    PG_RETURN_VOID();
}