brinfuncs.c

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/*
 * brinfuncs.c
 *      Functions to investigate BRIN indexes
 *
 * Copyright (c) 2014-2020, PostgreSQL Global Development Group
 *
 * IDENTIFICATION
 *      contrib/pageinspect/brinfuncs.c
 */
#include "postgres.h"

#include "access/brin.h"
#include "access/brin_internal.h"
#include "access/brin_page.h"
#include "access/brin_revmap.h"
#include "access/brin_tuple.h"
#include "access/htup_details.h"
#include "catalog/index.h"
#include "catalog/pg_type.h"
#include "funcapi.h"
#include "lib/stringinfo.h"
#include "miscadmin.h"
#include "pageinspect.h"
#include "utils/array.h"
#include "utils/builtins.h"
#include "utils/lsyscache.h"
#include "utils/rel.h"

PG_FUNCTION_INFO_V1(brin_page_type);
PG_FUNCTION_INFO_V1(brin_page_items);
PG_FUNCTION_INFO_V1(brin_metapage_info);
PG_FUNCTION_INFO_V1(brin_revmap_data);

typedef struct brin_column_state
{
    int         nstored;
    FmgrInfo    outputFn[FLEXIBLE_ARRAY_MEMBER];
} brin_column_state;


static Page verify_brin_page(bytea *raw_page, uint16 type,
                             const char *strtype);

Datum
brin_page_type(PG_FUNCTION_ARGS)
{
    bytea      *raw_page = PG_GETARG_BYTEA_P(0);
    Page        page = VARDATA(raw_page);
    int         raw_page_size;
    char       *type;

    if (!superuser())
        ereport(ERROR,
                (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
                 (errmsg("must be superuser to use raw page functions"))));

    raw_page_size = VARSIZE(raw_page) - VARHDRSZ;

    if (raw_page_size != BLCKSZ)
        ereport(ERROR,
                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                 errmsg("input page too small"),
                 errdetail("Expected size %d, got %d",
                           BLCKSZ, raw_page_size)));

    switch (BrinPageType(page))
    {
        case BRIN_PAGETYPE_META:
            type = "meta";
            break;
        case BRIN_PAGETYPE_REVMAP:
            type = "revmap";
            break;
        case BRIN_PAGETYPE_REGULAR:
            type = "regular";
            break;
        default:
            type = psprintf("unknown (%02x)", BrinPageType(page));
            break;
    }

    PG_RETURN_TEXT_P(cstring_to_text(type));
}

/*
 * Verify that the given bytea contains a BRIN page of the indicated page
 * type, or die in the attempt.  A pointer to the page is returned.
 */
static Page
verify_brin_page(bytea *raw_page, uint16 type, const char *strtype)
{
    Page        page;
    int         raw_page_size;

    raw_page_size = VARSIZE(raw_page) - VARHDRSZ;

    if (raw_page_size != BLCKSZ)
        ereport(ERROR,
                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                 errmsg("input page too small"),
                 errdetail("Expected size %d, got %d",
                           BLCKSZ, raw_page_size)));

    page = VARDATA(raw_page);

    /* verify the special space says this page is what we want */
    if (BrinPageType(page) != type)
        ereport(ERROR,
                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                 errmsg("page is not a BRIN page of type \"%s\"", strtype),
                 errdetail("Expected special type %08x, got %08x.",
                           type, BrinPageType(page))));

    return page;
}


/*
 * Extract all item values from a BRIN index page
 *
 * Usage: SELECT * FROM brin_page_items(get_raw_page('idx', 1), 'idx'::regclass);
 */
Datum
brin_page_items(PG_FUNCTION_ARGS)
{
    bytea      *raw_page = PG_GETARG_BYTEA_P(0);
    Oid         indexRelid = PG_GETARG_OID(1);
    ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
    TupleDesc   tupdesc;
    MemoryContext oldcontext;
    Tuplestorestate *tupstore;
    Relation    indexRel;
    brin_column_state **columns;
    BrinDesc   *bdesc;
    BrinMemTuple *dtup;
    Page        page;
    OffsetNumber offset;
    AttrNumber  attno;
    bool        unusedItem;

    if (!superuser())
        ereport(ERROR,
                (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
                 (errmsg("must be superuser to use raw page functions"))));

    /* check to see if caller supports us returning a tuplestore */
    if (rsinfo == NULL || !IsA(rsinfo, ReturnSetInfo))
        ereport(ERROR,
                (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                 errmsg("set-valued function called in context that cannot accept a set")));
    if (!(rsinfo->allowedModes & SFRM_Materialize) ||
        rsinfo->expectedDesc == NULL)
        ereport(ERROR,
                (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                 errmsg("materialize mode required, but it is not allowed in this context")));

    /* Build a tuple descriptor for our result type */
    if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
        elog(ERROR, "return type must be a row type");

    /* Build tuplestore to hold the result rows */
    oldcontext = MemoryContextSwitchTo(rsinfo->econtext->ecxt_per_query_memory);

    tupstore = tuplestore_begin_heap(true, false, work_mem);
    rsinfo->returnMode = SFRM_Materialize;
    rsinfo->setResult = tupstore;
    rsinfo->setDesc = tupdesc;

    MemoryContextSwitchTo(oldcontext);

    indexRel = index_open(indexRelid, AccessShareLock);
    bdesc = brin_build_desc(indexRel);

    /* minimally verify the page we got */
    page = verify_brin_page(raw_page, BRIN_PAGETYPE_REGULAR, "regular");

    /*
     * Initialize output functions for all indexed datatypes; simplifies
     * calling them later.
     */
    columns = palloc(sizeof(brin_column_state *) * RelationGetDescr(indexRel)->natts);
    for (attno = 1; attno <= bdesc->bd_tupdesc->natts; attno++)
    {
        Oid         output;
        bool        isVarlena;
        BrinOpcInfo *opcinfo;
        int         i;
        brin_column_state *column;

        opcinfo = bdesc->bd_info[attno - 1];
        column = palloc(offsetof(brin_column_state, outputFn) +
                        sizeof(FmgrInfo) * opcinfo->oi_nstored);

        column->nstored = opcinfo->oi_nstored;
        for (i = 0; i < opcinfo->oi_nstored; i++)
        {
            getTypeOutputInfo(opcinfo->oi_typcache[i]->type_id, &output, &isVarlena);
            fmgr_info(output, &column->outputFn[i]);
        }

        columns[attno - 1] = column;
    }

    offset = FirstOffsetNumber;
    unusedItem = false;
    dtup = NULL;
    for (;;)
    {
        Datum       values[7];
        bool        nulls[7];

        /*
         * This loop is called once for every attribute of every tuple in the
         * page.  At the start of a tuple, we get a NULL dtup; that's our
         * signal for obtaining and decoding the next one.  If that's not the
         * case, we output the next attribute.
         */
        if (dtup == NULL)
        {
            ItemId      itemId;

            /* verify item status: if there's no data, we can't decode */
            itemId = PageGetItemId(page, offset);
            if (ItemIdIsUsed(itemId))
            {
                dtup = brin_deform_tuple(bdesc,
                                         (BrinTuple *) PageGetItem(page, itemId),
                                         NULL);
                attno = 1;
                unusedItem = false;
            }
            else
                unusedItem = true;
        }
        else
            attno++;

        MemSet(nulls, 0, sizeof(nulls));

        if (unusedItem)
        {
            values[0] = UInt16GetDatum(offset);
            nulls[1] = true;
            nulls[2] = true;
            nulls[3] = true;
            nulls[4] = true;
            nulls[5] = true;
            nulls[6] = true;
        }
        else
        {
            int         att = attno - 1;

            values[0] = UInt16GetDatum(offset);
            values[1] = UInt32GetDatum(dtup->bt_blkno);
            values[2] = UInt16GetDatum(attno);
            values[3] = BoolGetDatum(dtup->bt_columns[att].bv_allnulls);
            values[4] = BoolGetDatum(dtup->bt_columns[att].bv_hasnulls);
            values[5] = BoolGetDatum(dtup->bt_placeholder);
            if (!dtup->bt_columns[att].bv_allnulls)
            {
                BrinValues *bvalues = &dtup->bt_columns[att];
                StringInfoData s;
                bool        first;
                int         i;

                initStringInfo(&s);
                appendStringInfoChar(&s, '{');

                first = true;
                for (i = 0; i < columns[att]->nstored; i++)
                {
                    char       *val;

                    if (!first)
                        appendStringInfoString(&s, " .. ");
                    first = false;
                    val = OutputFunctionCall(&columns[att]->outputFn[i],
                                             bvalues->bv_values[i]);
                    appendStringInfoString(&s, val);
                    pfree(val);
                }
                appendStringInfoChar(&s, '}');

                values[6] = CStringGetTextDatum(s.data);
                pfree(s.data);
            }
            else
            {
                nulls[6] = true;
            }
        }

        tuplestore_putvalues(tupstore, tupdesc, values, nulls);

        /*
         * If the item was unused, jump straight to the next one; otherwise,
         * the only cleanup needed here is to set our signal to go to the next
         * tuple in the following iteration, by freeing the current one.
         */
        if (unusedItem)
            offset = OffsetNumberNext(offset);
        else if (attno >= bdesc->bd_tupdesc->natts)
        {
            pfree(dtup);
            dtup = NULL;
            offset = OffsetNumberNext(offset);
        }

        /*
         * If we're beyond the end of the page, we're done.
         */
        if (offset > PageGetMaxOffsetNumber(page))
            break;
    }

    /* clean up and return the tuplestore */
    brin_free_desc(bdesc);
    tuplestore_donestoring(tupstore);
    index_close(indexRel, AccessShareLock);

    return (Datum) 0;
}

Datum
brin_metapage_info(PG_FUNCTION_ARGS)
{
    bytea      *raw_page = PG_GETARG_BYTEA_P(0);
    Page        page;
    BrinMetaPageData *meta;
    TupleDesc   tupdesc;
    Datum       values[4];
    bool        nulls[4];
    HeapTuple   htup;

    if (!superuser())
        ereport(ERROR,
                (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
                 (errmsg("must be superuser to use raw page functions"))));

    page = verify_brin_page(raw_page, BRIN_PAGETYPE_META, "metapage");

    /* Build a tuple descriptor for our result type */
    if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
        elog(ERROR, "return type must be a row type");
    tupdesc = BlessTupleDesc(tupdesc);

    /* Extract values from the metapage */
    meta = (BrinMetaPageData *) PageGetContents(page);
    MemSet(nulls, 0, sizeof(nulls));
    values[0] = CStringGetTextDatum(psprintf("0x%08X", meta->brinMagic));
    values[1] = Int32GetDatum(meta->brinVersion);
    values[2] = Int32GetDatum(meta->pagesPerRange);
    values[3] = Int64GetDatum(meta->lastRevmapPage);

    htup = heap_form_tuple(tupdesc, values, nulls);

    PG_RETURN_DATUM(HeapTupleGetDatum(htup));
}

/*
 * Return the TID array stored in a BRIN revmap page
 */
Datum
brin_revmap_data(PG_FUNCTION_ARGS)
{
    struct
    {
        ItemPointerData *tids;
        int         idx;
    }          *state;
    FuncCallContext *fctx;

    if (!superuser())
        ereport(ERROR,
                (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
                 (errmsg("must be superuser to use raw page functions"))));

    if (SRF_IS_FIRSTCALL())
    {
        bytea      *raw_page = PG_GETARG_BYTEA_P(0);
        MemoryContext mctx;
        Page        page;

        /* minimally verify the page we got */
        page = verify_brin_page(raw_page, BRIN_PAGETYPE_REVMAP, "revmap");

        /* create a function context for cross-call persistence */
        fctx = SRF_FIRSTCALL_INIT();

        /* switch to memory context appropriate for multiple function calls */
        mctx = MemoryContextSwitchTo(fctx->multi_call_memory_ctx);

        state = palloc(sizeof(*state));
        state->tids = ((RevmapContents *) PageGetContents(page))->rm_tids;
        state->idx = 0;

        fctx->user_fctx = state;

        MemoryContextSwitchTo(mctx);
    }

    fctx = SRF_PERCALL_SETUP();
    state = fctx->user_fctx;

    if (state->idx < REVMAP_PAGE_MAXITEMS)
        SRF_RETURN_NEXT(fctx, PointerGetDatum(&state->tids[state->idx++]));

    SRF_RETURN_DONE(fctx);
}