ginutil.c

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/*-------------------------------------------------------------------------
 *
 * ginutil.c
 *    utilities routines for the postgres inverted index access method.
 *
 *
 * Portions Copyright (c) 1996-2013, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * IDENTIFICATION
 *          src/backend/access/gin/ginutil.c
 *-------------------------------------------------------------------------
 */

#include "postgres.h"

#include "access/gin_private.h"
#include "access/reloptions.h"
#include "catalog/pg_collation.h"
#include "catalog/pg_type.h"
#include "miscadmin.h"
#include "storage/indexfsm.h"
#include "storage/lmgr.h"


/*
 * initGinState: fill in an empty GinState struct to describe the index
 *
 * Note: assorted subsidiary data is allocated in the CurrentMemoryContext.
 */
void
initGinState(GinState *state, Relation index)
{
    TupleDesc   origTupdesc = RelationGetDescr(index);
    int         i;

    MemSet(state, 0, sizeof(GinState));

    state->index = index;
    state->oneCol = (origTupdesc->natts == 1) ? true : false;
    state->origTupdesc = origTupdesc;

    for (i = 0; i < origTupdesc->natts; i++)
    {
        if (state->oneCol)
            state->tupdesc[i] = state->origTupdesc;
        else
        {
            state->tupdesc[i] = CreateTemplateTupleDesc(2, false);

            TupleDescInitEntry(state->tupdesc[i], (AttrNumber) 1, NULL,
                               INT2OID, -1, 0);
            TupleDescInitEntry(state->tupdesc[i], (AttrNumber) 2, NULL,
                               origTupdesc->attrs[i]->atttypid,
                               origTupdesc->attrs[i]->atttypmod,
                               origTupdesc->attrs[i]->attndims);
            TupleDescInitEntryCollation(state->tupdesc[i], (AttrNumber) 2,
                                        origTupdesc->attrs[i]->attcollation);
        }

        fmgr_info_copy(&(state->compareFn[i]),
                       index_getprocinfo(index, i + 1, GIN_COMPARE_PROC),
                       CurrentMemoryContext);
        fmgr_info_copy(&(state->extractValueFn[i]),
                       index_getprocinfo(index, i + 1, GIN_EXTRACTVALUE_PROC),
                       CurrentMemoryContext);
        fmgr_info_copy(&(state->extractQueryFn[i]),
                       index_getprocinfo(index, i + 1, GIN_EXTRACTQUERY_PROC),
                       CurrentMemoryContext);
        fmgr_info_copy(&(state->consistentFn[i]),
                       index_getprocinfo(index, i + 1, GIN_CONSISTENT_PROC),
                       CurrentMemoryContext);

        /*
         * Check opclass capability to do partial match.
         */
        if (index_getprocid(index, i + 1, GIN_COMPARE_PARTIAL_PROC) != InvalidOid)
        {
            fmgr_info_copy(&(state->comparePartialFn[i]),
                   index_getprocinfo(index, i + 1, GIN_COMPARE_PARTIAL_PROC),
                           CurrentMemoryContext);
            state->canPartialMatch[i] = true;
        }
        else
        {
            state->canPartialMatch[i] = false;
        }

        /*
         * If the index column has a specified collation, we should honor that
         * while doing comparisons.  However, we may have a collatable storage
         * type for a noncollatable indexed data type (for instance, hstore
         * uses text index entries).  If there's no index collation then
         * specify default collation in case the support functions need
         * collation.  This is harmless if the support functions don't care
         * about collation, so we just do it unconditionally.  (We could
         * alternatively call get_typcollation, but that seems like expensive
         * overkill --- there aren't going to be any cases where a GIN storage
         * type has a nondefault collation.)
         */
        if (OidIsValid(index->rd_indcollation[i]))
            state->supportCollation[i] = index->rd_indcollation[i];
        else
            state->supportCollation[i] = DEFAULT_COLLATION_OID;
    }
}

/*
 * Extract attribute (column) number of stored entry from GIN tuple
 */
OffsetNumber
gintuple_get_attrnum(GinState *ginstate, IndexTuple tuple)
{
    OffsetNumber colN;

    if (ginstate->oneCol)
    {
        /* column number is not stored explicitly */
        colN = FirstOffsetNumber;
    }
    else
    {
        Datum       res;
        bool        isnull;

        /*
         * First attribute is always int16, so we can safely use any tuple
         * descriptor to obtain first attribute of tuple
         */
        res = index_getattr(tuple, FirstOffsetNumber, ginstate->tupdesc[0],
                            &isnull);
        Assert(!isnull);

        colN = DatumGetUInt16(res);
        Assert(colN >= FirstOffsetNumber && colN <= ginstate->origTupdesc->natts);
    }

    return colN;
}

/*
 * Extract stored datum (and possible null category) from GIN tuple
 */
Datum
gintuple_get_key(GinState *ginstate, IndexTuple tuple,
                 GinNullCategory *category)
{
    Datum       res;
    bool        isnull;

    if (ginstate->oneCol)
    {
        /*
         * Single column index doesn't store attribute numbers in tuples
         */
        res = index_getattr(tuple, FirstOffsetNumber, ginstate->origTupdesc,
                            &isnull);
    }
    else
    {
        /*
         * Since the datum type depends on which index column it's from, we
         * must be careful to use the right tuple descriptor here.
         */
        OffsetNumber colN = gintuple_get_attrnum(ginstate, tuple);

        res = index_getattr(tuple, OffsetNumberNext(FirstOffsetNumber),
                            ginstate->tupdesc[colN - 1],
                            &isnull);
    }

    if (isnull)
        *category = GinGetNullCategory(tuple, ginstate);
    else
        *category = GIN_CAT_NORM_KEY;

    return res;
}

/*
 * 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 GinInitBuffer
 */
Buffer
GinNewBuffer(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 (GinPageIsDeleted(page))
                return buffer;  /* OK to use */

            LockBuffer(buffer, GIN_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, GIN_EXCLUSIVE);

    if (needLock)
        UnlockRelationForExtension(index, ExclusiveLock);

    return buffer;
}

void
GinInitPage(Page page, uint32 f, Size pageSize)
{
    GinPageOpaque opaque;

    PageInit(page, pageSize, sizeof(GinPageOpaqueData));

    opaque = GinPageGetOpaque(page);
    memset(opaque, 0, sizeof(GinPageOpaqueData));
    opaque->flags = f;
    opaque->rightlink = InvalidBlockNumber;
}

void
GinInitBuffer(Buffer b, uint32 f)
{
    GinInitPage(BufferGetPage(b), f, BufferGetPageSize(b));
}

void
GinInitMetabuffer(Buffer b)
{
    GinMetaPageData *metadata;
    Page        page = BufferGetPage(b);

    GinInitPage(page, GIN_META, BufferGetPageSize(b));

    metadata = GinPageGetMeta(page);

    metadata->head = metadata->tail = InvalidBlockNumber;
    metadata->tailFreeSize = 0;
    metadata->nPendingPages = 0;
    metadata->nPendingHeapTuples = 0;
    metadata->nTotalPages = 0;
    metadata->nEntryPages = 0;
    metadata->nDataPages = 0;
    metadata->nEntries = 0;
    metadata->ginVersion = GIN_CURRENT_VERSION;
}

/*
 * Compare two keys of the same index column
 */
int
ginCompareEntries(GinState *ginstate, OffsetNumber attnum,
                  Datum a, GinNullCategory categorya,
                  Datum b, GinNullCategory categoryb)
{
    /* if not of same null category, sort by that first */
    if (categorya != categoryb)
        return (categorya < categoryb) ? -1 : 1;

    /* all null items in same category are equal */
    if (categorya != GIN_CAT_NORM_KEY)
        return 0;

    /* both not null, so safe to call the compareFn */
    return DatumGetInt32(FunctionCall2Coll(&ginstate->compareFn[attnum - 1],
                                      ginstate->supportCollation[attnum - 1],
                                           a, b));
}

/*
 * Compare two keys of possibly different index columns
 */
int
ginCompareAttEntries(GinState *ginstate,
                     OffsetNumber attnuma, Datum a, GinNullCategory categorya,
                     OffsetNumber attnumb, Datum b, GinNullCategory categoryb)
{
    /* attribute number is the first sort key */
    if (attnuma != attnumb)
        return (attnuma < attnumb) ? -1 : 1;

    return ginCompareEntries(ginstate, attnuma, a, categorya, b, categoryb);
}


/*
 * Support for sorting key datums in ginExtractEntries
 *
 * Note: we only have to worry about null and not-null keys here;
 * ginExtractEntries never generates more than one placeholder null,
 * so it doesn't have to sort those.
 */
typedef struct
{
    Datum       datum;
    bool        isnull;
} keyEntryData;

typedef struct
{
    FmgrInfo   *cmpDatumFunc;
    Oid         collation;
    bool        haveDups;
} cmpEntriesArg;

static int
cmpEntries(const void *a, const void *b, void *arg)
{
    const keyEntryData *aa = (const keyEntryData *) a;
    const keyEntryData *bb = (const keyEntryData *) b;
    cmpEntriesArg *data = (cmpEntriesArg *) arg;
    int         res;

    if (aa->isnull)
    {
        if (bb->isnull)
            res = 0;            /* NULL "=" NULL */
        else
            res = 1;            /* NULL ">" not-NULL */
    }
    else if (bb->isnull)
        res = -1;               /* not-NULL "<" NULL */
    else
        res = DatumGetInt32(FunctionCall2Coll(data->cmpDatumFunc,
                                              data->collation,
                                              aa->datum, bb->datum));

    /*
     * Detect if we have any duplicates.  If there are equal keys, qsort must
     * compare them at some point, else it wouldn't know whether one should go
     * before or after the other.
     */
    if (res == 0)
        data->haveDups = true;

    return res;
}


/*
 * Extract the index key values from an indexable item
 *
 * The resulting key values are sorted, and any duplicates are removed.
 * This avoids generating redundant index entries.
 */
Datum *
ginExtractEntries(GinState *ginstate, OffsetNumber attnum,
                  Datum value, bool isNull,
                  int32 *nentries, GinNullCategory **categories)
{
    Datum      *entries;
    bool       *nullFlags;
    int32       i;

    /*
     * We don't call the extractValueFn on a null item.  Instead generate a
     * placeholder.
     */
    if (isNull)
    {
        *nentries = 1;
        entries = (Datum *) palloc(sizeof(Datum));
        entries[0] = (Datum) 0;
        *categories = (GinNullCategory *) palloc(sizeof(GinNullCategory));
        (*categories)[0] = GIN_CAT_NULL_ITEM;
        return entries;
    }

    /* OK, call the opclass's extractValueFn */
    nullFlags = NULL;           /* in case extractValue doesn't set it */
    entries = (Datum *)
        DatumGetPointer(FunctionCall3Coll(&ginstate->extractValueFn[attnum - 1],
                                      ginstate->supportCollation[attnum - 1],
                                          value,
                                          PointerGetDatum(nentries),
                                          PointerGetDatum(&nullFlags)));

    /*
     * Generate a placeholder if the item contained no keys.
     */
    if (entries == NULL || *nentries <= 0)
    {
        *nentries = 1;
        entries = (Datum *) palloc(sizeof(Datum));
        entries[0] = (Datum) 0;
        *categories = (GinNullCategory *) palloc(sizeof(GinNullCategory));
        (*categories)[0] = GIN_CAT_EMPTY_ITEM;
        return entries;
    }

    /*
     * If the extractValueFn didn't create a nullFlags array, create one,
     * assuming that everything's non-null.  Otherwise, run through the array
     * and make sure each value is exactly 0 or 1; this ensures binary
     * compatibility with the GinNullCategory representation.
     */
    if (nullFlags == NULL)
        nullFlags = (bool *) palloc0(*nentries * sizeof(bool));
    else
    {
        for (i = 0; i < *nentries; i++)
            nullFlags[i] = (nullFlags[i] ? true : false);
    }
    /* now we can use the nullFlags as category codes */
    *categories = (GinNullCategory *) nullFlags;

    /*
     * If there's more than one key, sort and unique-ify.
     *
     * XXX Using qsort here is notationally painful, and the overhead is
     * pretty bad too.  For small numbers of keys it'd likely be better to use
     * a simple insertion sort.
     */
    if (*nentries > 1)
    {
        keyEntryData *keydata;
        cmpEntriesArg arg;

        keydata = (keyEntryData *) palloc(*nentries * sizeof(keyEntryData));
        for (i = 0; i < *nentries; i++)
        {
            keydata[i].datum = entries[i];
            keydata[i].isnull = nullFlags[i];
        }

        arg.cmpDatumFunc = &ginstate->compareFn[attnum - 1];
        arg.collation = ginstate->supportCollation[attnum - 1];
        arg.haveDups = false;
        qsort_arg(keydata, *nentries, sizeof(keyEntryData),
                  cmpEntries, (void *) &arg);

        if (arg.haveDups)
        {
            /* there are duplicates, must get rid of 'em */
            int32       j;

            entries[0] = keydata[0].datum;
            nullFlags[0] = keydata[0].isnull;
            j = 1;
            for (i = 1; i < *nentries; i++)
            {
                if (cmpEntries(&keydata[i - 1], &keydata[i], &arg) != 0)
                {
                    entries[j] = keydata[i].datum;
                    nullFlags[j] = keydata[i].isnull;
                    j++;
                }
            }
            *nentries = j;
        }
        else
        {
            /* easy, no duplicates */
            for (i = 0; i < *nentries; i++)
            {
                entries[i] = keydata[i].datum;
                nullFlags[i] = keydata[i].isnull;
            }
        }

        pfree(keydata);
    }

    return entries;
}

Datum
ginoptions(PG_FUNCTION_ARGS)
{
    Datum       reloptions = PG_GETARG_DATUM(0);
    bool        validate = PG_GETARG_BOOL(1);
    relopt_value *options;
    GinOptions *rdopts;
    int         numoptions;
    static const relopt_parse_elt tab[] = {
        {"fastupdate", RELOPT_TYPE_BOOL, offsetof(GinOptions, useFastUpdate)}
    };

    options = parseRelOptions(reloptions, validate, RELOPT_KIND_GIN,
                              &numoptions);

    /* if none set, we're done */
    if (numoptions == 0)
        PG_RETURN_NULL();

    rdopts = allocateReloptStruct(sizeof(GinOptions), options, numoptions);

    fillRelOptions((void *) rdopts, sizeof(GinOptions), options, numoptions,
                   validate, tab, lengthof(tab));

    pfree(options);

    PG_RETURN_BYTEA_P(rdopts);
}

/*
 * Fetch index's statistical data into *stats
 *
 * Note: in the result, nPendingPages can be trusted to be up-to-date,
 * as can ginVersion; but the other fields are as of the last VACUUM.
 */
void
ginGetStats(Relation index, GinStatsData *stats)
{
    Buffer      metabuffer;
    Page        metapage;
    GinMetaPageData *metadata;

    metabuffer = ReadBuffer(index, GIN_METAPAGE_BLKNO);
    LockBuffer(metabuffer, GIN_SHARE);
    metapage = BufferGetPage(metabuffer);
    metadata = GinPageGetMeta(metapage);

    stats->nPendingPages = metadata->nPendingPages;
    stats->nTotalPages = metadata->nTotalPages;
    stats->nEntryPages = metadata->nEntryPages;
    stats->nDataPages = metadata->nDataPages;
    stats->nEntries = metadata->nEntries;
    stats->ginVersion = metadata->ginVersion;

    UnlockReleaseBuffer(metabuffer);
}

/*
 * Write the given statistics to the index's metapage
 *
 * Note: nPendingPages and ginVersion are *not* copied over
 */
void
ginUpdateStats(Relation index, const GinStatsData *stats)
{
    Buffer      metabuffer;
    Page        metapage;
    GinMetaPageData *metadata;

    metabuffer = ReadBuffer(index, GIN_METAPAGE_BLKNO);
    LockBuffer(metabuffer, GIN_EXCLUSIVE);
    metapage = BufferGetPage(metabuffer);
    metadata = GinPageGetMeta(metapage);

    START_CRIT_SECTION();

    metadata->nTotalPages = stats->nTotalPages;
    metadata->nEntryPages = stats->nEntryPages;
    metadata->nDataPages = stats->nDataPages;
    metadata->nEntries = stats->nEntries;

    MarkBufferDirty(metabuffer);

    if (RelationNeedsWAL(index))
    {
        XLogRecPtr  recptr;
        ginxlogUpdateMeta data;
        XLogRecData rdata;

        data.node = index->rd_node;
        data.ntuples = 0;
        data.newRightlink = data.prevTail = InvalidBlockNumber;
        memcpy(&data.metadata, metadata, sizeof(GinMetaPageData));

        rdata.buffer = InvalidBuffer;
        rdata.data = (char *) &data;
        rdata.len = sizeof(ginxlogUpdateMeta);
        rdata.next = NULL;

        recptr = XLogInsert(RM_GIN_ID, XLOG_GIN_UPDATE_META_PAGE, &rdata);
        PageSetLSN(metapage, recptr);
    }

    UnlockReleaseBuffer(metabuffer);

    END_CRIT_SECTION();
}