blutils.c

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/*-------------------------------------------------------------------------
 *
 * blutils.c
 *      Bloom index utilities.
 *
 * Portions Copyright (c) 2016-2019, PostgreSQL Global Development Group
 * Portions Copyright (c) 1990-1993, Regents of the University of California
 *
 * IDENTIFICATION
 *    contrib/bloom/blutils.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include "access/amapi.h"
#include "access/generic_xlog.h"
#include "access/reloptions.h"
#include "bloom.h"
#include "catalog/index.h"
#include "miscadmin.h"
#include "storage/bufmgr.h"
#include "storage/freespace.h"
#include "storage/indexfsm.h"
#include "storage/lmgr.h"
#include "utils/memutils.h"

/* Signature dealing macros - note i is assumed to be of type int */
#define GETWORD(x,i) ( *( (BloomSignatureWord *)(x) + ( (i) / SIGNWORDBITS ) ) )
#define CLRBIT(x,i)   GETWORD(x,i) &= ~( 0x01 << ( (i) % SIGNWORDBITS ) )
#define SETBIT(x,i)   GETWORD(x,i) |=  ( 0x01 << ( (i) % SIGNWORDBITS ) )
#define GETBIT(x,i) ( (GETWORD(x,i) >> ( (i) % SIGNWORDBITS )) & 0x01 )

PG_FUNCTION_INFO_V1(blhandler);

/* Kind of relation options for bloom index */
static relopt_kind bl_relopt_kind;

/* parse table for fillRelOptions */
static relopt_parse_elt bl_relopt_tab[INDEX_MAX_KEYS + 1];

static int32 myRand(void);
static void mySrand(uint32 seed);

/*
 * Module initialize function: initialize info about Bloom relation options.
 *
 * Note: keep this in sync with makeDefaultBloomOptions().
 */
void
_PG_init(void)
{
    int         i;
    char        buf[16];

    bl_relopt_kind = add_reloption_kind();

    /* Option for length of signature */
    add_int_reloption(bl_relopt_kind, "length",
                      "Length of signature in bits",
                      DEFAULT_BLOOM_LENGTH, 1, MAX_BLOOM_LENGTH,
                      AccessExclusiveLock);
    bl_relopt_tab[0].optname = "length";
    bl_relopt_tab[0].opttype = RELOPT_TYPE_INT;
    bl_relopt_tab[0].offset = offsetof(BloomOptions, bloomLength);

    /* Number of bits for each possible index column: col1, col2, ... */
    for (i = 0; i < INDEX_MAX_KEYS; i++)
    {
        snprintf(buf, sizeof(buf), "col%d", i + 1);
        add_int_reloption(bl_relopt_kind, buf,
                          "Number of bits generated for each index column",
                          DEFAULT_BLOOM_BITS, 1, MAX_BLOOM_BITS,
                          AccessExclusiveLock);
        bl_relopt_tab[i + 1].optname = MemoryContextStrdup(TopMemoryContext,
                                                           buf);
        bl_relopt_tab[i + 1].opttype = RELOPT_TYPE_INT;
        bl_relopt_tab[i + 1].offset = offsetof(BloomOptions, bitSize[0]) + sizeof(int) * i;
    }
}

/*
 * Construct a default set of Bloom options.
 */
static BloomOptions *
makeDefaultBloomOptions(void)
{
    BloomOptions *opts;
    int         i;

    opts = (BloomOptions *) palloc0(sizeof(BloomOptions));
    /* Convert DEFAULT_BLOOM_LENGTH from # of bits to # of words */
    opts->bloomLength = (DEFAULT_BLOOM_LENGTH + SIGNWORDBITS - 1) / SIGNWORDBITS;
    for (i = 0; i < INDEX_MAX_KEYS; i++)
        opts->bitSize[i] = DEFAULT_BLOOM_BITS;
    SET_VARSIZE(opts, sizeof(BloomOptions));
    return opts;
}

/*
 * Bloom handler function: return IndexAmRoutine with access method parameters
 * and callbacks.
 */
Datum
blhandler(PG_FUNCTION_ARGS)
{
    IndexAmRoutine *amroutine = makeNode(IndexAmRoutine);

    amroutine->amstrategies = BLOOM_NSTRATEGIES;
    amroutine->amsupport = BLOOM_NPROC;
    amroutine->amcanorder = false;
    amroutine->amcanorderbyop = false;
    amroutine->amcanbackward = false;
    amroutine->amcanunique = false;
    amroutine->amcanmulticol = true;
    amroutine->amoptionalkey = true;
    amroutine->amsearcharray = false;
    amroutine->amsearchnulls = false;
    amroutine->amstorage = false;
    amroutine->amclusterable = false;
    amroutine->ampredlocks = false;
    amroutine->amcanparallel = false;
    amroutine->amcaninclude = false;
    amroutine->amkeytype = InvalidOid;

    amroutine->ambuild = blbuild;
    amroutine->ambuildempty = blbuildempty;
    amroutine->aminsert = blinsert;
    amroutine->ambulkdelete = blbulkdelete;
    amroutine->amvacuumcleanup = blvacuumcleanup;
    amroutine->amcanreturn = NULL;
    amroutine->amcostestimate = blcostestimate;
    amroutine->amoptions = bloptions;
    amroutine->amproperty = NULL;
    amroutine->ambuildphasename = NULL;
    amroutine->amvalidate = blvalidate;
    amroutine->ambeginscan = blbeginscan;
    amroutine->amrescan = blrescan;
    amroutine->amgettuple = NULL;
    amroutine->amgetbitmap = blgetbitmap;
    amroutine->amendscan = blendscan;
    amroutine->ammarkpos = NULL;
    amroutine->amrestrpos = NULL;
    amroutine->amestimateparallelscan = NULL;
    amroutine->aminitparallelscan = NULL;
    amroutine->amparallelrescan = NULL;

    PG_RETURN_POINTER(amroutine);
}

/*
 * Fill BloomState structure for particular index.
 */
void
initBloomState(BloomState *state, Relation index)
{
    int         i;

    state->nColumns = index->rd_att->natts;

    /* Initialize hash function for each attribute */
    for (i = 0; i < index->rd_att->natts; i++)
    {
        fmgr_info_copy(&(state->hashFn[i]),
                       index_getprocinfo(index, i + 1, BLOOM_HASH_PROC),
                       CurrentMemoryContext);
        state->collations[i] = index->rd_indcollation[i];
    }

    /* Initialize amcache if needed with options from metapage */
    if (!index->rd_amcache)
    {
        Buffer      buffer;
        Page        page;
        BloomMetaPageData *meta;
        BloomOptions *opts;

        opts = MemoryContextAlloc(index->rd_indexcxt, sizeof(BloomOptions));

        buffer = ReadBuffer(index, BLOOM_METAPAGE_BLKNO);
        LockBuffer(buffer, BUFFER_LOCK_SHARE);

        page = BufferGetPage(buffer);

        if (!BloomPageIsMeta(page))
            elog(ERROR, "Relation is not a bloom index");
        meta = BloomPageGetMeta(BufferGetPage(buffer));

        if (meta->magickNumber != BLOOM_MAGICK_NUMBER)
            elog(ERROR, "Relation is not a bloom index");

        *opts = meta->opts;

        UnlockReleaseBuffer(buffer);

        index->rd_amcache = (void *) opts;
    }

    memcpy(&state->opts, index->rd_amcache, sizeof(state->opts));
    state->sizeOfBloomTuple = BLOOMTUPLEHDRSZ +
        sizeof(BloomSignatureWord) * state->opts.bloomLength;
}

/*
 * Random generator copied from FreeBSD.  Using own random generator here for
 * two reasons:
 *
 * 1) In this case random numbers are used for on-disk storage.  Usage of
 *    PostgreSQL number generator would obstruct it from all possible changes.
 * 2) Changing seed of PostgreSQL random generator would be undesirable side
 *    effect.
 */
static int32 next;

static int32
myRand(void)
{
    /*----------
     * Compute x = (7^5 * x) mod (2^31 - 1)
     * without overflowing 31 bits:
     *      (2^31 - 1) = 127773 * (7^5) + 2836
     * From "Random number generators: good ones are hard to find",
     * Park and Miller, Communications of the ACM, vol. 31, no. 10,
     * October 1988, p. 1195.
     *----------
     */
    int32       hi,
                lo,
                x;

    /* Must be in [1, 0x7ffffffe] range at this point. */
    hi = next / 127773;
    lo = next % 127773;
    x = 16807 * lo - 2836 * hi;
    if (x < 0)
        x += 0x7fffffff;
    next = x;
    /* Transform to [0, 0x7ffffffd] range. */
    return (x - 1);
}

static void
mySrand(uint32 seed)
{
    next = seed;
    /* Transform to [1, 0x7ffffffe] range. */
    next = (next % 0x7ffffffe) + 1;
}

/*
 * Add bits of given value to the signature.
 */
void
signValue(BloomState *state, BloomSignatureWord *sign, Datum value, int attno)
{
    uint32      hashVal;
    int         nBit,
                j;

    /*
     * init generator with "column's" number to get "hashed" seed for new
     * value. We don't want to map the same numbers from different columns
     * into the same bits!
     */
    mySrand(attno);

    /*
     * Init hash sequence to map our value into bits. the same values in
     * different columns will be mapped into different bits because of step
     * above
     */
    hashVal = DatumGetInt32(FunctionCall1Coll(&state->hashFn[attno], state->collations[attno], value));
    mySrand(hashVal ^ myRand());

    for (j = 0; j < state->opts.bitSize[attno]; j++)
    {
        /* prevent multiple evaluation in SETBIT macro */
        nBit = myRand() % (state->opts.bloomLength * SIGNWORDBITS);
        SETBIT(sign, nBit);
    }
}

/*
 * Make bloom tuple from values.
 */
BloomTuple *
BloomFormTuple(BloomState *state, ItemPointer iptr, Datum *values, bool *isnull)
{
    int         i;
    BloomTuple *res = (BloomTuple *) palloc0(state->sizeOfBloomTuple);

    res->heapPtr = *iptr;

    /* Blooming each column */
    for (i = 0; i < state->nColumns; i++)
    {
        /* skip nulls */
        if (isnull[i])
            continue;

        signValue(state, res->sign, values[i], i);
    }

    return res;
}

/*
 * Add new bloom tuple to the page.  Returns true if new tuple was successfully
 * added to the page.  Returns false if it doesn't fit on the page.
 */
bool
BloomPageAddItem(BloomState *state, Page page, BloomTuple *tuple)
{
    BloomTuple *itup;
    BloomPageOpaque opaque;
    Pointer     ptr;

    /* We shouldn't be pointed to an invalid page */
    Assert(!PageIsNew(page) && !BloomPageIsDeleted(page));

    /* Does new tuple fit on the page? */
    if (BloomPageGetFreeSpace(state, page) < state->sizeOfBloomTuple)
        return false;

    /* Copy new tuple to the end of page */
    opaque = BloomPageGetOpaque(page);
    itup = BloomPageGetTuple(state, page, opaque->maxoff + 1);
    memcpy((Pointer) itup, (Pointer) tuple, state->sizeOfBloomTuple);

    /* Adjust maxoff and pd_lower */
    opaque->maxoff++;
    ptr = (Pointer) BloomPageGetTuple(state, page, opaque->maxoff + 1);
    ((PageHeader) page)->pd_lower = ptr - page;

    /* Assert we didn't overrun available space */
    Assert(((PageHeader) page)->pd_lower <= ((PageHeader) page)->pd_upper);

    return true;
}

/*
 * Allocate a new page (either by recycling, or by extending the index file)
 * The returned buffer is already pinned and exclusive-locked
 * Caller is responsible for initializing the page by calling BloomInitPage
 */
Buffer
BloomNewBuffer(Relation index)
{
    Buffer      buffer;
    bool        needLock;

    /* First, try to get a page from FSM */
    for (;;)
    {
        BlockNumber blkno = GetFreeIndexPage(index);

        if (blkno == InvalidBlockNumber)
            break;

        buffer = ReadBuffer(index, blkno);

        /*
         * We have to guard against the possibility that someone else already
         * recycled this page; the buffer may be locked if so.
         */
        if (ConditionalLockBuffer(buffer))
        {
            Page        page = BufferGetPage(buffer);

            if (PageIsNew(page))
                return buffer;  /* OK to use, if never initialized */

            if (BloomPageIsDeleted(page))
                return buffer;  /* OK to use */

            LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
        }

        /* Can't use it, so release buffer and try again */
        ReleaseBuffer(buffer);
    }

    /* Must extend the file */
    needLock = !RELATION_IS_LOCAL(index);
    if (needLock)
        LockRelationForExtension(index, ExclusiveLock);

    buffer = ReadBuffer(index, P_NEW);
    LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE);

    if (needLock)
        UnlockRelationForExtension(index, ExclusiveLock);

    return buffer;
}

/*
 * Initialize any page of a bloom index.
 */
void
BloomInitPage(Page page, uint16 flags)
{
    BloomPageOpaque opaque;

    PageInit(page, BLCKSZ, sizeof(BloomPageOpaqueData));

    opaque = BloomPageGetOpaque(page);
    memset(opaque, 0, sizeof(BloomPageOpaqueData));
    opaque->flags = flags;
    opaque->bloom_page_id = BLOOM_PAGE_ID;
}

/*
 * Fill in metapage for bloom index.
 */
void
BloomFillMetapage(Relation index, Page metaPage)
{
    BloomOptions *opts;
    BloomMetaPageData *metadata;

    /*
     * Choose the index's options.  If reloptions have been assigned, use
     * those, otherwise create default options.
     */
    opts = (BloomOptions *) index->rd_options;
    if (!opts)
        opts = makeDefaultBloomOptions();

    /*
     * Initialize contents of meta page, including a copy of the options,
     * which are now frozen for the life of the index.
     */
    BloomInitPage(metaPage, BLOOM_META);
    metadata = BloomPageGetMeta(metaPage);
    memset(metadata, 0, sizeof(BloomMetaPageData));
    metadata->magickNumber = BLOOM_MAGICK_NUMBER;
    metadata->opts = *opts;
    ((PageHeader) metaPage)->pd_lower += sizeof(BloomMetaPageData);

    /* If this fails, probably FreeBlockNumberArray size calc is wrong: */
    Assert(((PageHeader) metaPage)->pd_lower <= ((PageHeader) metaPage)->pd_upper);
}

/*
 * Initialize metapage for bloom index.
 */
void
BloomInitMetapage(Relation index)
{
    Buffer      metaBuffer;
    Page        metaPage;
    GenericXLogState *state;

    /*
     * Make a new page; since it is first page it should be associated with
     * block number 0 (BLOOM_METAPAGE_BLKNO).
     */
    metaBuffer = BloomNewBuffer(index);
    Assert(BufferGetBlockNumber(metaBuffer) == BLOOM_METAPAGE_BLKNO);

    /* Initialize contents of meta page */
    state = GenericXLogStart(index);
    metaPage = GenericXLogRegisterBuffer(state, metaBuffer,
                                         GENERIC_XLOG_FULL_IMAGE);
    BloomFillMetapage(index, metaPage);
    GenericXLogFinish(state);

    UnlockReleaseBuffer(metaBuffer);
}

/*
 * Parse reloptions for bloom index, producing a BloomOptions struct.
 */
bytea *
bloptions(Datum reloptions, bool validate)
{
    BloomOptions *rdopts;

    /* Parse the user-given reloptions */
    rdopts = (BloomOptions *) build_reloptions(reloptions, validate,
                                               bl_relopt_kind,
                                               sizeof(BloomOptions),
                                               bl_relopt_tab,
                                               lengthof(bl_relopt_tab));

    /* Convert signature length from # of bits to # to words, rounding up */
    if (rdopts)
        rdopts->bloomLength = (rdopts->bloomLength + SIGNWORDBITS - 1) / SIGNWORDBITS;

    return (bytea *) rdopts;
}