brinfuncs.c

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/*
 * brinfuncs.c
 *      Functions to investigate BRIN indexes
 *
 * Copyright (c) 2014-2025, PostgreSQL Global Development Group
 *
 * IDENTIFICATION
 *      contrib/pageinspect/brinfuncs.c
 */
#include "postgres.h"
 
#include "access/brin_internal.h"
#include "access/brin_page.h"
#include "access/brin_tuple.h"
#include "access/htup_details.h"
#include "catalog/pg_am_d.h"
#include "catalog/pg_type.h"
#include "funcapi.h"
#include "lib/stringinfo.h"
#include "miscadmin.h"
#include "pageinspect.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);
 
#define IS_BRIN(r) ((r)->rd_rel->relam == BRIN_AM_OID)
 
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;
    char       *type;
 
    if (!superuser())
        ereport(ERROR,
                (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
                 errmsg("must be superuser to use raw page functions")));
 
    page = get_page_from_raw(raw_page);
 
    if (PageIsNew(page))
        PG_RETURN_NULL();
 
    /* verify the special space has the expected size */
    if (PageGetSpecialSize(page) != MAXALIGN(sizeof(BrinSpecialSpace)))
        ereport(ERROR,
                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                 errmsg("input page is not a valid %s page", "BRIN"),
                 errdetail("Expected special size %d, got %d.",
                           (int) MAXALIGN(sizeof(BrinSpecialSpace)),
                           (int) PageGetSpecialSize(page))));
 
    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 = get_page_from_raw(raw_page);
 
    if (PageIsNew(page))
        return page;
 
    /* verify the special space has the expected size */
    if (PageGetSpecialSize(page) != MAXALIGN(sizeof(BrinSpecialSpace)))
        ereport(ERROR,
                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                 errmsg("input page is not a valid %s page", "BRIN"),
                 errdetail("Expected special size %d, got %d.",
                           (int) MAXALIGN(sizeof(BrinSpecialSpace)),
                           (int) PageGetSpecialSize(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;
}
 
/* Number of output arguments (columns) for brin_page_items() */
#define BRIN_PAGE_ITEMS_V1_12   8
 
/*
 * 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;
    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")));
 
    InitMaterializedSRF(fcinfo, 0);
 
    /*
     * Version 1.12 added a new output column for the empty range flag. But as
     * it was added in the middle, it may cause crashes with function
     * definitions from older versions of the extension.
     *
     * There is no way to reliably avoid the problems created by the old
     * function definition at this point, so insist that the user update the
     * extension.
     */
    if (rsinfo->setDesc->natts < BRIN_PAGE_ITEMS_V1_12)
        ereport(ERROR,
                (errcode(ERRCODE_INVALID_FUNCTION_DEFINITION),
                 errmsg("function has wrong number of declared columns"),
                 errhint("To resolve the problem, update the \"pageinspect\" extension to the latest version.")));
 
    indexRel = index_open(indexRelid, AccessShareLock);
 
    if (!IS_BRIN(indexRel))
        ereport(ERROR,
                (errcode(ERRCODE_WRONG_OBJECT_TYPE),
                 errmsg("\"%s\" is not a %s index",
                        RelationGetRelationName(indexRel), "BRIN")));
 
    bdesc = brin_build_desc(indexRel);
 
    /* minimally verify the page we got */
    page = verify_brin_page(raw_page, BRIN_PAGETYPE_REGULAR, "regular");
 
    if (PageIsNew(page))
    {
        brin_free_desc(bdesc);
        index_close(indexRel, AccessShareLock);
        PG_RETURN_NULL();
    }
 
    /*
     * 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[8];
        bool        nulls[8] = {0};
 
        /*
         * 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++;
 
        if (unusedItem)
        {
            values[0] = UInt16GetDatum(offset);
            nulls[1] = true;
            nulls[2] = true;
            nulls[3] = true;
            nulls[4] = true;
            nulls[5] = true;
            nulls[6] = true;
            nulls[7] = true;
        }
        else
        {
            int         att = attno - 1;
 
            values[0] = UInt16GetDatum(offset);
            switch (TupleDescAttr(rsinfo->setDesc, 1)->atttypid)
            {
                case INT8OID:
                    values[1] = Int64GetDatum((int64) dtup->bt_blkno);
                    break;
                case INT4OID:
                    /* support for old extension version */
                    values[1] = UInt32GetDatum(dtup->bt_blkno);
                    break;
                default:
                    elog(ERROR, "incorrect output types");
            }
            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);
            values[6] = BoolGetDatum(dtup->bt_empty_range);
            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[7] = CStringGetTextDatum(s.data);
                pfree(s.data);
            }
            else
            {
                nulls[7] = true;
            }
        }
 
        tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, 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;
    }
 
    brin_free_desc(bdesc);
    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] = {0};
    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");
 
    if (PageIsNew(page))
        PG_RETURN_NULL();
 
    /* 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);
    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;
 
        /* 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);
 
        /* minimally verify the page we got */
        page = verify_brin_page(raw_page, BRIN_PAGETYPE_REVMAP, "revmap");
 
        if (PageIsNew(page))
        {
            MemoryContextSwitchTo(mctx);
            PG_RETURN_NULL();
        }
 
        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);
}