brin_bloom.c File Reference

#include "postgres.h"
#include "access/genam.h"
#include "access/brin.h"
#include "access/brin_internal.h"
#include "access/brin_page.h"
#include "access/brin_tuple.h"
#include "access/hash.h"
#include "access/htup_details.h"
#include "access/reloptions.h"
#include "access/stratnum.h"
#include "catalog/pg_type.h"
#include "catalog/pg_amop.h"
#include "utils/builtins.h"
#include "utils/datum.h"
#include "utils/lsyscache.h"
#include "utils/rel.h"
#include "utils/syscache.h"
#include <math.h>

Include dependency graph for brin_bloom.c:

Go to the source code of this file.

Data Structures
struct	BloomOptions
struct	BloomFilter
struct	BloomOpaque

Macros
#define	BloomEqualStrategyNumber   1
#define	BLOOM_MAX_PROCNUMS   1 /* maximum support procs we need */
#define	PROCNUM_HASH   11 /* required */
#define	PROCNUM_BASE   11
#define	BLOOM_MIN_NDISTINCT_PER_RANGE   16
#define	BLOOM_DEFAULT_NDISTINCT_PER_RANGE   -0.1 /* 10% of values */
#define	BLOOM_MIN_FALSE_POSITIVE_RATE   0.0001 /* 0.01% fp rate */
#define	BLOOM_MAX_FALSE_POSITIVE_RATE   0.25 /* 25% fp rate */
#define	BLOOM_DEFAULT_FALSE_POSITIVE_RATE   0.01 /* 1% fp rate */
#define	BloomGetNDistinctPerRange(opts)
#define	BloomGetFalsePositiveRate(opts)
#define	BloomMaxFilterSize
#define	BLOOM_SEED_1   0x71d924af
#define	BLOOM_SEED_2   0xba48b314

Typedefs
typedef struct BloomOptions	BloomOptions
typedef struct BloomFilter	BloomFilter
typedef struct BloomOpaque	BloomOpaque

Functions
static BloomFilter *	bloom_init (int ndistinct, double false_positive_rate)
static BloomFilter *	bloom_add_value (BloomFilter *filter, uint32 value, bool *updated)
static bool	bloom_contains_value (BloomFilter *filter, uint32 value)
static FmgrInfo *	bloom_get_procinfo (BrinDesc *bdesc, uint16 attno, uint16 procnum)
Datum	brin_bloom_opcinfo (PG_FUNCTION_ARGS)
static int	brin_bloom_get_ndistinct (BrinDesc *bdesc, BloomOptions *opts)
Datum	brin_bloom_add_value (PG_FUNCTION_ARGS)
Datum	brin_bloom_consistent (PG_FUNCTION_ARGS)
Datum	brin_bloom_union (PG_FUNCTION_ARGS)
Datum	brin_bloom_options (PG_FUNCTION_ARGS)
Datum	brin_bloom_summary_in (PG_FUNCTION_ARGS)
Datum	brin_bloom_summary_out (PG_FUNCTION_ARGS)
Datum	brin_bloom_summary_recv (PG_FUNCTION_ARGS)
Datum	brin_bloom_summary_send (PG_FUNCTION_ARGS)

Macro Definition Documentation

BLOOM_DEFAULT_FALSE_POSITIVE_RATE

#define BLOOM_DEFAULT_FALSE_POSITIVE_RATE   0.01 /* 1% fp rate */

Definition at line 197 of file brin_bloom.c.

BLOOM_DEFAULT_NDISTINCT_PER_RANGE

#define BLOOM_DEFAULT_NDISTINCT_PER_RANGE   -0.1 /* 10% of values */

Definition at line 179 of file brin_bloom.c.

BLOOM_MAX_FALSE_POSITIVE_RATE

#define BLOOM_MAX_FALSE_POSITIVE_RATE   0.25 /* 25% fp rate */

Definition at line 196 of file brin_bloom.c.

BLOOM_MAX_PROCNUMS

#define BLOOM_MAX_PROCNUMS   1 /* maximum support procs we need */

Definition at line 145 of file brin_bloom.c.

BLOOM_MIN_FALSE_POSITIVE_RATE

#define BLOOM_MIN_FALSE_POSITIVE_RATE   0.0001 /* 0.01% fp rate */

Definition at line 195 of file brin_bloom.c.

BLOOM_MIN_NDISTINCT_PER_RANGE

#define BLOOM_MIN_NDISTINCT_PER_RANGE   16

Definition at line 172 of file brin_bloom.c.

BLOOM_SEED_1

#define BLOOM_SEED_1   0x71d924af

Definition at line 225 of file brin_bloom.c.

BLOOM_SEED_2

#define BLOOM_SEED_2   0xba48b314

Definition at line 226 of file brin_bloom.c.

BloomEqualStrategyNumber

#define BloomEqualStrategyNumber   1

Definition at line 136 of file brin_bloom.c.

BloomGetFalsePositiveRate

#define BloomGetFalsePositiveRate

(

opts

)

Value:

    ((opts) && (((BloomOptions *) (opts))->falsePositiveRate != 0.0) ? \
     (((BloomOptions *) (opts))->falsePositiveRate) : \
     BLOOM_DEFAULT_FALSE_POSITIVE_RATE)

Definition at line 204 of file brin_bloom.c.

BloomGetNDistinctPerRange

#define BloomGetNDistinctPerRange

(

opts

)

Value:

    ((opts) && (((BloomOptions *) (opts))->nDistinctPerRange != 0) ? \
     (((BloomOptions *) (opts))->nDistinctPerRange) : \
     BLOOM_DEFAULT_NDISTINCT_PER_RANGE)

Definition at line 199 of file brin_bloom.c.

BloomMaxFilterSize

#define BloomMaxFilterSize

Value:

    MAXALIGN_DOWN(BLCKSZ - \
                  (MAXALIGN(SizeOfPageHeaderData + \
                            sizeof(ItemIdData)) + \
                   MAXALIGN(sizeof(BrinSpecialSpace)) + \
                   SizeOfBrinTuple))

Definition at line 214 of file brin_bloom.c.

PROCNUM_BASE

#define PROCNUM_BASE   11

Definition at line 152 of file brin_bloom.c.

PROCNUM_HASH

#define PROCNUM_HASH   11 /* required */

Definition at line 146 of file brin_bloom.c.

Typedef Documentation

BloomFilter

typedef struct BloomFilter BloomFilter

BloomOpaque

typedef struct BloomOpaque BloomOpaque

BloomOptions

typedef struct BloomOptions BloomOptions

Function Documentation

bloom_add_value()

static BloomFilter* bloom_add_value ( BloomFilter *  filter, uint32  value, bool *  updated  )

static

Definition at line 343 of file brin_bloom.c.

{
    int         i;
    uint64      h1,
                h2;
 
    /* compute the hashes, used for the bloom filter */
    h1 = hash_bytes_uint32_extended(value, BLOOM_SEED_1) % filter->nbits;
    h2 = hash_bytes_uint32_extended(value, BLOOM_SEED_2) % filter->nbits;
 
    /* compute the requested number of hashes */
    for (i = 0; i < filter->nhashes; i++)
    {
        /* h1 + h2 + f(i) */
        uint32      h = (h1 + i * h2) % filter->nbits;
        uint32      byte = (h / 8);
        uint32      bit = (h % 8);
 
        /* if the bit is not set, set it and remember we did that */
        if (!(filter->data[byte] & (0x01 << bit)))
        {
            filter->data[byte] |= (0x01 << bit);
            filter->nbits_set++;
            if (updated)
                *updated = true;
        }
    }
 
    return filter;
}

References bit(), BLOOM_SEED_1, BLOOM_SEED_2, BloomFilter::data, hash_bytes_uint32_extended(), i, BloomFilter::nbits, BloomFilter::nbits_set, BloomFilter::nhashes, and value.

Referenced by brin_bloom_add_value().

bloom_contains_value()

static bool bloom_contains_value ( BloomFilter *  filter, uint32  value  )

static

Definition at line 380 of file brin_bloom.c.

{
    int         i;
    uint64      h1,
                h2;
 
    /* calculate the two hashes */
    h1 = hash_bytes_uint32_extended(value, BLOOM_SEED_1) % filter->nbits;
    h2 = hash_bytes_uint32_extended(value, BLOOM_SEED_2) % filter->nbits;
 
    /* compute the requested number of hashes */
    for (i = 0; i < filter->nhashes; i++)
    {
        /* h1 + h2 + f(i) */
        uint32      h = (h1 + i * h2) % filter->nbits;
        uint32      byte = (h / 8);
        uint32      bit = (h % 8);
 
        /* if the bit is not set, the value is not there */
        if (!(filter->data[byte] & (0x01 << bit)))
            return false;
    }
 
    /* all hashes found in bloom filter */
    return true;
}

References bit(), BLOOM_SEED_1, BLOOM_SEED_2, BloomFilter::data, hash_bytes_uint32_extended(), i, BloomFilter::nbits, BloomFilter::nhashes, and value.

Referenced by brin_bloom_consistent().

bloom_get_procinfo()

static FmgrInfo * bloom_get_procinfo ( BrinDesc *  bdesc, uint16  attno, uint16  procnum  )

static

Definition at line 674 of file brin_bloom.c.

{
    BloomOpaque *opaque;
    uint16      basenum = procnum - PROCNUM_BASE;
 
    /*
     * We cache these in the opaque struct, to avoid repetitive syscache
     * lookups.
     */
    opaque = (BloomOpaque *) bdesc->bd_info[attno - 1]->oi_opaque;
 
    /*
     * If we already searched for this proc and didn't find it, don't bother
     * searching again.
     */
    if (opaque->extra_proc_missing[basenum])
        return NULL;
 
    if (opaque->extra_procinfos[basenum].fn_oid == InvalidOid)
    {
        if (RegProcedureIsValid(index_getprocid(bdesc->bd_index, attno,
                                                procnum)))
        {
            fmgr_info_copy(&opaque->extra_procinfos[basenum],
                           index_getprocinfo(bdesc->bd_index, attno, procnum),
                           bdesc->bd_context);
        }
        else
        {
            opaque->extra_proc_missing[basenum] = true;
            return NULL;
        }
    }
 
    return &opaque->extra_procinfos[basenum];
}

References BrinDesc::bd_context, BrinDesc::bd_index, BrinDesc::bd_info, BloomOpaque::extra_proc_missing, BloomOpaque::extra_procinfos, fmgr_info_copy(), FmgrInfo::fn_oid, if(), index_getprocid(), index_getprocinfo(), InvalidOid, BrinOpcInfo::oi_opaque, PROCNUM_BASE, and RegProcedureIsValid.

Referenced by brin_bloom_add_value(), and brin_bloom_consistent().

bloom_init()

static BloomFilter* bloom_init ( int  ndistinct, double  false_positive_rate  )

static

Definition at line 271 of file brin_bloom.c.

{
    Size        len;
    BloomFilter *filter;
 
    int         nbits;          /* size of filter / number of bits */
    int         nbytes;         /* size of filter / number of bytes */
 
    double      k;              /* number of hash functions */
 
    Assert(ndistinct > 0);
    Assert((false_positive_rate >= BLOOM_MIN_FALSE_POSITIVE_RATE) &&
           (false_positive_rate < BLOOM_MAX_FALSE_POSITIVE_RATE));
 
    /* sizing bloom filter: -(n * ln(p)) / (ln(2))^2 */
    nbits = ceil(-(ndistinct * log(false_positive_rate)) / pow(log(2.0), 2));
 
    /* round m to whole bytes */
    nbytes = ((nbits + 7) / 8);
    nbits = nbytes * 8;
 
    /*
     * Reject filters that are obviously too large to store on a page.
     *
     * Initially the bloom filter is just zeroes and so very compressible, but
     * as we add values it gets more and more random, and so less and less
     * compressible. So initially everything fits on the page, but we might
     * get surprising failures later - we want to prevent that, so we reject
     * bloom filter that are obviously too large.
     *
     * XXX It's not uncommon to oversize the bloom filter a bit, to defend
     * against unexpected data anomalies (parts of table with more distinct
     * values per range etc.). But we still need to make sure even the
     * oversized filter fits on page, if such need arises.
     *
     * XXX This check is not perfect, because the index may have multiple
     * filters that are small individually, but too large when combined.
     */
    if (nbytes > BloomMaxFilterSize)
        elog(ERROR, "the bloom filter is too large (%d > %zu)", nbytes,
             BloomMaxFilterSize);
 
    /*
     * round(log(2.0) * m / ndistinct), but assume round() may not be
     * available on Windows
     */
    k = log(2.0) * nbits / ndistinct;
    k = (k - floor(k) >= 0.5) ? ceil(k) : floor(k);
 
    /*
     * We allocate the whole filter. Most of it is going to be 0 bits, so the
     * varlena is easy to compress.
     */
    len = offsetof(BloomFilter, data) + nbytes;
 
    filter = (BloomFilter *) palloc0(len);
 
    filter->flags = 0;
    filter->nhashes = (int) k;
    filter->nbits = nbits;
 
    SET_VARSIZE(filter, len);
 
    return filter;
}

References Assert(), BLOOM_MAX_FALSE_POSITIVE_RATE, BLOOM_MIN_FALSE_POSITIVE_RATE, BloomMaxFilterSize, data, elog(), ERROR, BloomFilter::flags, len, BloomFilter::nbits, BloomFilter::nhashes, palloc0(), and SET_VARSIZE.

Referenced by brin_bloom_add_value().

brin_bloom_add_value()

Datum brin_bloom_add_value

(

PG_FUNCTION_ARGS

)

Definition at line 513 of file brin_bloom.c.

{
    BrinDesc   *bdesc = (BrinDesc *) PG_GETARG_POINTER(0);
    BrinValues *column = (BrinValues *) PG_GETARG_POINTER(1);
    Datum       newval = PG_GETARG_DATUM(2);
    bool        isnull PG_USED_FOR_ASSERTS_ONLY = PG_GETARG_DATUM(3);
    BloomOptions *opts = (BloomOptions *) PG_GET_OPCLASS_OPTIONS();
    Oid         colloid = PG_GET_COLLATION();
    FmgrInfo   *hashFn;
    uint32      hashValue;
    bool        updated = false;
    AttrNumber  attno;
    BloomFilter *filter;
 
    Assert(!isnull);
 
    attno = column->bv_attno;
 
    /*
     * If this is the first non-null value, we need to initialize the bloom
     * filter. Otherwise just extract the existing bloom filter from
     * BrinValues.
     */
    if (column->bv_allnulls)
    {
        filter = bloom_init(brin_bloom_get_ndistinct(bdesc, opts),
                            BloomGetFalsePositiveRate(opts));
        column->bv_values[0] = PointerGetDatum(filter);
        column->bv_allnulls = false;
        updated = true;
    }
    else
        filter = (BloomFilter *) PG_DETOAST_DATUM(column->bv_values[0]);
 
    /*
     * Compute the hash of the new value, using the supplied hash function,
     * and then add the hash value to the bloom filter.
     */
    hashFn = bloom_get_procinfo(bdesc, attno, PROCNUM_HASH);
 
    hashValue = DatumGetUInt32(FunctionCall1Coll(hashFn, colloid, newval));
 
    filter = bloom_add_value(filter, hashValue, &updated);
 
    column->bv_values[0] = PointerGetDatum(filter);
 
    PG_RETURN_BOOL(updated);
}

References Assert(), bloom_add_value(), bloom_get_procinfo(), bloom_init(), BloomGetFalsePositiveRate, brin_bloom_get_ndistinct(), BrinValues::bv_allnulls, BrinValues::bv_attno, BrinValues::bv_values, DatumGetUInt32(), FunctionCall1Coll(), newval, opts, PG_DETOAST_DATUM, PG_GET_COLLATION, PG_GET_OPCLASS_OPTIONS, PG_GETARG_DATUM, PG_GETARG_POINTER, PG_RETURN_BOOL, PG_USED_FOR_ASSERTS_ONLY, PointerGetDatum(), and PROCNUM_HASH.

brin_bloom_consistent()

Datum brin_bloom_consistent

(

PG_FUNCTION_ARGS

)

Definition at line 568 of file brin_bloom.c.

{
    BrinDesc   *bdesc = (BrinDesc *) PG_GETARG_POINTER(0);
    BrinValues *column = (BrinValues *) PG_GETARG_POINTER(1);
    ScanKey    *keys = (ScanKey *) PG_GETARG_POINTER(2);
    int         nkeys = PG_GETARG_INT32(3);
    Oid         colloid = PG_GET_COLLATION();
    AttrNumber  attno;
    Datum       value;
    Datum       matches;
    FmgrInfo   *finfo;
    uint32      hashValue;
    BloomFilter *filter;
    int         keyno;
 
    filter = (BloomFilter *) PG_DETOAST_DATUM(column->bv_values[0]);
 
    Assert(filter);
 
    matches = true;
 
    for (keyno = 0; keyno < nkeys; keyno++)
    {
        ScanKey     key = keys[keyno];
 
        /* NULL keys are handled and filtered-out in bringetbitmap */
        Assert(!(key->sk_flags & SK_ISNULL));
 
        attno = key->sk_attno;
        value = key->sk_argument;
 
        switch (key->sk_strategy)
        {
            case BloomEqualStrategyNumber:
 
                /*
                 * In the equality case (WHERE col = someval), we want to
                 * return the current page range if the minimum value in the
                 * range <= scan key, and the maximum value >= scan key.
                 */
                finfo = bloom_get_procinfo(bdesc, attno, PROCNUM_HASH);
 
                hashValue = DatumGetUInt32(FunctionCall1Coll(finfo, colloid, value));
                matches &= bloom_contains_value(filter, hashValue);
 
                break;
            default:
                /* shouldn't happen */
                elog(ERROR, "invalid strategy number %d", key->sk_strategy);
                matches = 0;
                break;
        }
 
        if (!matches)
            break;
    }
 
    PG_RETURN_DATUM(matches);
}

References Assert(), bloom_contains_value(), bloom_get_procinfo(), BloomEqualStrategyNumber, BrinValues::bv_values, DatumGetUInt32(), elog(), ERROR, FunctionCall1Coll(), sort-test::key, PG_DETOAST_DATUM, PG_GET_COLLATION, PG_GETARG_INT32, PG_GETARG_POINTER, PG_RETURN_DATUM, PROCNUM_HASH, SK_ISNULL, and value.

brin_bloom_get_ndistinct()

static int brin_bloom_get_ndistinct ( BrinDesc *  bdesc, BloomOptions *  opts  )

static

Definition at line 470 of file brin_bloom.c.

{
    double      ndistinct;
    double      maxtuples;
    BlockNumber pagesPerRange;
 
    pagesPerRange = BrinGetPagesPerRange(bdesc->bd_index);
    ndistinct = BloomGetNDistinctPerRange(opts);
 
    Assert(BlockNumberIsValid(pagesPerRange));
 
    maxtuples = MaxHeapTuplesPerPage * pagesPerRange;
 
    /*
     * Similarly to n_distinct, negative values are relative - in this case to
     * maximum number of tuples in the page range (maxtuples).
     */
    if (ndistinct < 0)
        ndistinct = (-ndistinct) * maxtuples;
 
    /*
     * Positive values are to be used directly, but we still apply a couple of
     * safeties to avoid using unreasonably small bloom filters.
     */
    ndistinct = Max(ndistinct, BLOOM_MIN_NDISTINCT_PER_RANGE);
 
    /*
     * And don't use more than the maximum possible number of tuples, in the
     * range, which would be entirely wasteful.
     */
    ndistinct = Min(ndistinct, maxtuples);
 
    return (int) ndistinct;
}

References Assert(), BrinDesc::bd_index, BlockNumberIsValid(), BLOOM_MIN_NDISTINCT_PER_RANGE, BloomGetNDistinctPerRange, BrinGetPagesPerRange, Max, MaxHeapTuplesPerPage, Min, and opts.

Referenced by brin_bloom_add_value().

brin_bloom_opcinfo()

Datum brin_bloom_opcinfo

(

PG_FUNCTION_ARGS

)

Definition at line 423 of file brin_bloom.c.

{
    BrinOpcInfo *result;
 
    /*
     * opaque->strategy_procinfos is initialized lazily; here it is set to
     * all-uninitialized by palloc0 which sets fn_oid to InvalidOid.
     *
     * bloom indexes only store the filter as a single BYTEA column
     */
 
    result = palloc0(MAXALIGN(SizeofBrinOpcInfo(1)) +
                     sizeof(BloomOpaque));
    result->oi_nstored = 1;
    result->oi_regular_nulls = true;
    result->oi_opaque = (BloomOpaque *)
        MAXALIGN((char *) result + SizeofBrinOpcInfo(1));
    result->oi_typcache[0] = lookup_type_cache(PG_BRIN_BLOOM_SUMMARYOID, 0);
 
    PG_RETURN_POINTER(result);
}

References lookup_type_cache(), MAXALIGN, BrinOpcInfo::oi_nstored, BrinOpcInfo::oi_opaque, BrinOpcInfo::oi_regular_nulls, BrinOpcInfo::oi_typcache, palloc0(), PG_RETURN_POINTER, and SizeofBrinOpcInfo.

brin_bloom_options()

Datum brin_bloom_options

(

PG_FUNCTION_ARGS

)

Definition at line 712 of file brin_bloom.c.

{
    local_relopts *relopts = (local_relopts *) PG_GETARG_POINTER(0);
 
    init_local_reloptions(relopts, sizeof(BloomOptions));
 
    add_local_real_reloption(relopts, "n_distinct_per_range",
                             "number of distinct items expected in a BRIN page range",
                             BLOOM_DEFAULT_NDISTINCT_PER_RANGE,
                             -1.0, INT_MAX, offsetof(BloomOptions, nDistinctPerRange));
 
    add_local_real_reloption(relopts, "false_positive_rate",
                             "desired false-positive rate for the bloom filters",
                             BLOOM_DEFAULT_FALSE_POSITIVE_RATE,
                             BLOOM_MIN_FALSE_POSITIVE_RATE,
                             BLOOM_MAX_FALSE_POSITIVE_RATE,
                             offsetof(BloomOptions, falsePositiveRate));
 
    PG_RETURN_VOID();
}

References add_local_real_reloption(), BLOOM_DEFAULT_FALSE_POSITIVE_RATE, BLOOM_DEFAULT_NDISTINCT_PER_RANGE, BLOOM_MAX_FALSE_POSITIVE_RATE, BLOOM_MIN_FALSE_POSITIVE_RATE, init_local_reloptions(), PG_GETARG_POINTER, and PG_RETURN_VOID.

brin_bloom_summary_in()

Datum brin_bloom_summary_in

(

PG_FUNCTION_ARGS

)

Definition at line 742 of file brin_bloom.c.

{
    /*
     * brin_bloom_summary stores the data in binary form and parsing text
     * input is not needed, so disallow this.
     */
    ereport(ERROR,
            (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
             errmsg("cannot accept a value of type %s", "pg_brin_bloom_summary")));
 
    PG_RETURN_VOID();           /* keep compiler quiet */
}

References ereport, errcode(), errmsg(), ERROR, and PG_RETURN_VOID.

brin_bloom_summary_out()

Datum brin_bloom_summary_out

(

PG_FUNCTION_ARGS

)

Definition at line 764 of file brin_bloom.c.

{
    BloomFilter *filter;
    StringInfoData str;
 
    /* detoast the data to get value with a full 4B header */
    filter = (BloomFilter *) PG_DETOAST_DATUM_PACKED(PG_GETARG_DATUM(0));
 
    initStringInfo(&str);
    appendStringInfoChar(&str, '{');
 
    appendStringInfo(&str, "mode: hashed  nhashes: %u  nbits: %u  nbits_set: %u",
                     filter->nhashes, filter->nbits, filter->nbits_set);
 
    appendStringInfoChar(&str, '}');
 
    PG_RETURN_CSTRING(str.data);
}

References appendStringInfo(), appendStringInfoChar(), initStringInfo(), BloomFilter::nbits, BloomFilter::nbits_set, BloomFilter::nhashes, PG_DETOAST_DATUM_PACKED, PG_GETARG_DATUM, PG_RETURN_CSTRING, and generate_unaccent_rules::str.

brin_bloom_summary_recv()

Datum brin_bloom_summary_recv

(

PG_FUNCTION_ARGS

)

Definition at line 788 of file brin_bloom.c.

{
    ereport(ERROR,
            (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
             errmsg("cannot accept a value of type %s", "pg_brin_bloom_summary")));
 
    PG_RETURN_VOID();           /* keep compiler quiet */
}

References ereport, errcode(), errmsg(), ERROR, and PG_RETURN_VOID.

brin_bloom_summary_send()

Datum brin_bloom_summary_send

(

PG_FUNCTION_ARGS

)

Definition at line 805 of file brin_bloom.c.

{
    return byteasend(fcinfo);
}

References byteasend().

brin_bloom_union()

Datum brin_bloom_union

(

PG_FUNCTION_ARGS

)

Definition at line 637 of file brin_bloom.c.

{
    int         i;
    int         nbytes;
    BrinValues *col_a = (BrinValues *) PG_GETARG_POINTER(1);
    BrinValues *col_b = (BrinValues *) PG_GETARG_POINTER(2);
    BloomFilter *filter_a;
    BloomFilter *filter_b;
 
    Assert(col_a->bv_attno == col_b->bv_attno);
    Assert(!col_a->bv_allnulls && !col_b->bv_allnulls);
 
    filter_a = (BloomFilter *) PG_DETOAST_DATUM(col_a->bv_values[0]);
    filter_b = (BloomFilter *) PG_DETOAST_DATUM(col_b->bv_values[0]);
 
    /* make sure the filters use the same parameters */
    Assert(filter_a && filter_b);
    Assert(filter_a->nbits == filter_b->nbits);
    Assert(filter_a->nhashes == filter_b->nhashes);
    Assert((filter_a->nbits > 0) && (filter_a->nbits % 8 == 0));
 
    nbytes = (filter_a->nbits) / 8;
 
    /* simply OR the bitmaps */
    for (i = 0; i < nbytes; i++)
        filter_a->data[i] |= filter_b->data[i];
 
    PG_RETURN_VOID();
}

References Assert(), BrinValues::bv_allnulls, BrinValues::bv_attno, BrinValues::bv_values, BloomFilter::data, i, BloomFilter::nbits, BloomFilter::nhashes, PG_DETOAST_DATUM, PG_GETARG_POINTER, and PG_RETURN_VOID.