btreefuncs.c

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/*
 * contrib/pageinspect/btreefuncs.c
 *
 *
 * btreefuncs.c
 *
 * Copyright (c) 2006 Satoshi Nagayasu <nagayasus@nttdata.co.jp>
 *
 * Permission to use, copy, modify, and distribute this software and
 * its documentation for any purpose, without fee, and without a
 * written agreement is hereby granted, provided that the above
 * copyright notice and this paragraph and the following two
 * paragraphs appear in all copies.
 *
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE TO ANY PARTY FOR DIRECT,
 * INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES, INCLUDING
 * LOST PROFITS, ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS
 * DOCUMENTATION, EVEN IF THE UNIVERSITY OF CALIFORNIA HAS BEEN ADVISED
 * OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * THE AUTHOR SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE.  THE SOFTWARE PROVIDED HEREUNDER IS ON AN "AS
 * IS" BASIS, AND THE AUTHOR HAS NO OBLIGATIONS TO PROVIDE MAINTENANCE,
 * SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
 */

#include "postgres.h"

#include "pageinspect.h"

#include "access/nbtree.h"
#include "catalog/namespace.h"
#include "catalog/pg_am.h"
#include "funcapi.h"
#include "miscadmin.h"
#include "utils/builtins.h"
#include "utils/rel.h"
#include "utils/varlena.h"


PG_FUNCTION_INFO_V1(bt_metap);
PG_FUNCTION_INFO_V1(bt_page_items);
PG_FUNCTION_INFO_V1(bt_page_items_bytea);
PG_FUNCTION_INFO_V1(bt_page_stats);

#define IS_INDEX(r) ((r)->rd_rel->relkind == RELKIND_INDEX)
#define IS_BTREE(r) ((r)->rd_rel->relam == BTREE_AM_OID)

/* note: BlockNumber is unsigned, hence can't be negative */
#define CHECK_RELATION_BLOCK_RANGE(rel, blkno) { \
        if ( RelationGetNumberOfBlocks(rel) <= (BlockNumber) (blkno) ) \
             elog(ERROR, "block number out of range"); }

/* ------------------------------------------------
 * structure for single btree page statistics
 * ------------------------------------------------
 */
typedef struct BTPageStat
{
    uint32      blkno;
    uint32      live_items;
    uint32      dead_items;
    uint32      page_size;
    uint32      max_avail;
    uint32      free_size;
    uint32      avg_item_size;
    char        type;

    /* opaque data */
    BlockNumber btpo_prev;
    BlockNumber btpo_next;
    union
    {
        uint32      level;
        TransactionId xact;
    }           btpo;
    uint16      btpo_flags;
    BTCycleId   btpo_cycleid;
} BTPageStat;


/* -------------------------------------------------
 * GetBTPageStatistics()
 *
 * Collect statistics of single b-tree page
 * -------------------------------------------------
 */
static void
GetBTPageStatistics(BlockNumber blkno, Buffer buffer, BTPageStat *stat)
{
    Page        page = BufferGetPage(buffer);
    PageHeader  phdr = (PageHeader) page;
    OffsetNumber maxoff = PageGetMaxOffsetNumber(page);
    BTPageOpaque opaque = (BTPageOpaque) PageGetSpecialPointer(page);
    int         item_size = 0;
    int         off;

    stat->blkno = blkno;

    stat->max_avail = BLCKSZ - (BLCKSZ - phdr->pd_special + SizeOfPageHeaderData);

    stat->dead_items = stat->live_items = 0;

    stat->page_size = PageGetPageSize(page);

    /* page type (flags) */
    if (P_ISDELETED(opaque))
    {
        stat->type = 'd';
        stat->btpo.xact = opaque->btpo.xact;
        return;
    }
    else if (P_IGNORE(opaque))
        stat->type = 'e';
    else if (P_ISLEAF(opaque))
        stat->type = 'l';
    else if (P_ISROOT(opaque))
        stat->type = 'r';
    else
        stat->type = 'i';

    /* btpage opaque data */
    stat->btpo_prev = opaque->btpo_prev;
    stat->btpo_next = opaque->btpo_next;
    stat->btpo.level = opaque->btpo.level;
    stat->btpo_flags = opaque->btpo_flags;
    stat->btpo_cycleid = opaque->btpo_cycleid;

    /* count live and dead tuples, and free space */
    for (off = FirstOffsetNumber; off <= maxoff; off++)
    {
        IndexTuple  itup;

        ItemId      id = PageGetItemId(page, off);

        itup = (IndexTuple) PageGetItem(page, id);

        item_size += IndexTupleSize(itup);

        if (!ItemIdIsDead(id))
            stat->live_items++;
        else
            stat->dead_items++;
    }
    stat->free_size = PageGetFreeSpace(page);

    if ((stat->live_items + stat->dead_items) > 0)
        stat->avg_item_size = item_size / (stat->live_items + stat->dead_items);
    else
        stat->avg_item_size = 0;
}

/* -----------------------------------------------
 * bt_page_stats()
 *
 * Usage: SELECT * FROM bt_page_stats('t1_pkey', 1);
 * -----------------------------------------------
 */
Datum
bt_page_stats(PG_FUNCTION_ARGS)
{
    text       *relname = PG_GETARG_TEXT_PP(0);
    uint32      blkno = PG_GETARG_UINT32(1);
    Buffer      buffer;
    Relation    rel;
    RangeVar   *relrv;
    Datum       result;
    HeapTuple   tuple;
    TupleDesc   tupleDesc;
    int         j;
    char       *values[11];
    BTPageStat  stat;

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

    relrv = makeRangeVarFromNameList(textToQualifiedNameList(relname));
    rel = relation_openrv(relrv, AccessShareLock);

    if (!IS_INDEX(rel) || !IS_BTREE(rel))
        elog(ERROR, "relation \"%s\" is not a btree index",
             RelationGetRelationName(rel));

    /*
     * Reject attempts to read non-local temporary relations; we would be
     * likely to get wrong data since we have no visibility into the owning
     * session's local buffers.
     */
    if (RELATION_IS_OTHER_TEMP(rel))
        ereport(ERROR,
                (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                 errmsg("cannot access temporary tables of other sessions")));

    if (blkno == 0)
        elog(ERROR, "block 0 is a meta page");

    CHECK_RELATION_BLOCK_RANGE(rel, blkno);

    buffer = ReadBuffer(rel, blkno);
    LockBuffer(buffer, BUFFER_LOCK_SHARE);

    /* keep compiler quiet */
    stat.btpo_prev = stat.btpo_next = InvalidBlockNumber;
    stat.btpo_flags = stat.free_size = stat.avg_item_size = 0;

    GetBTPageStatistics(blkno, buffer, &stat);

    UnlockReleaseBuffer(buffer);
    relation_close(rel, AccessShareLock);

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

    j = 0;
    values[j++] = psprintf("%d", stat.blkno);
    values[j++] = psprintf("%c", stat.type);
    values[j++] = psprintf("%d", stat.live_items);
    values[j++] = psprintf("%d", stat.dead_items);
    values[j++] = psprintf("%d", stat.avg_item_size);
    values[j++] = psprintf("%d", stat.page_size);
    values[j++] = psprintf("%d", stat.free_size);
    values[j++] = psprintf("%d", stat.btpo_prev);
    values[j++] = psprintf("%d", stat.btpo_next);
    values[j++] = psprintf("%d", (stat.type == 'd') ? stat.btpo.xact : stat.btpo.level);
    values[j++] = psprintf("%d", stat.btpo_flags);

    tuple = BuildTupleFromCStrings(TupleDescGetAttInMetadata(tupleDesc),
                                   values);

    result = HeapTupleGetDatum(tuple);

    PG_RETURN_DATUM(result);
}


/*
 * cross-call data structure for SRF
 */
struct user_args
{
    Page        page;
    OffsetNumber offset;
};

/*-------------------------------------------------------
 * bt_page_print_tuples()
 *
 * Form a tuple describing index tuple at a given offset
 * ------------------------------------------------------
 */
static Datum
bt_page_print_tuples(FuncCallContext *fctx, Page page, OffsetNumber offset)
{
    char       *values[6];
    HeapTuple   tuple;
    ItemId      id;
    IndexTuple  itup;
    int         j;
    int         off;
    int         dlen;
    char       *dump;
    char       *ptr;

    id = PageGetItemId(page, offset);

    if (!ItemIdIsValid(id))
        elog(ERROR, "invalid ItemId");

    itup = (IndexTuple) PageGetItem(page, id);

    j = 0;
    values[j++] = psprintf("%d", offset);
    values[j++] = psprintf("(%u,%u)",
                           ItemPointerGetBlockNumberNoCheck(&itup->t_tid),
                           ItemPointerGetOffsetNumberNoCheck(&itup->t_tid));
    values[j++] = psprintf("%d", (int) IndexTupleSize(itup));
    values[j++] = psprintf("%c", IndexTupleHasNulls(itup) ? 't' : 'f');
    values[j++] = psprintf("%c", IndexTupleHasVarwidths(itup) ? 't' : 'f');

    ptr = (char *) itup + IndexInfoFindDataOffset(itup->t_info);
    dlen = IndexTupleSize(itup) - IndexInfoFindDataOffset(itup->t_info);
    dump = palloc0(dlen * 3 + 1);
    values[j] = dump;
    for (off = 0; off < dlen; off++)
    {
        if (off > 0)
            *dump++ = ' ';
        sprintf(dump, "%02x", *(ptr + off) & 0xff);
        dump += 2;
    }

    tuple = BuildTupleFromCStrings(fctx->attinmeta, values);

    return HeapTupleGetDatum(tuple);
}

/*-------------------------------------------------------
 * bt_page_items()
 *
 * Get IndexTupleData set in a btree page
 *
 * Usage: SELECT * FROM bt_page_items('t1_pkey', 1);
 *-------------------------------------------------------
 */
Datum
bt_page_items(PG_FUNCTION_ARGS)
{
    text       *relname = PG_GETARG_TEXT_PP(0);
    uint32      blkno = PG_GETARG_UINT32(1);
    Datum       result;
    FuncCallContext *fctx;
    MemoryContext mctx;
    struct user_args *uargs;

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

    if (SRF_IS_FIRSTCALL())
    {
        RangeVar   *relrv;
        Relation    rel;
        Buffer      buffer;
        BTPageOpaque opaque;
        TupleDesc   tupleDesc;

        fctx = SRF_FIRSTCALL_INIT();

        relrv = makeRangeVarFromNameList(textToQualifiedNameList(relname));
        rel = relation_openrv(relrv, AccessShareLock);

        if (!IS_INDEX(rel) || !IS_BTREE(rel))
            elog(ERROR, "relation \"%s\" is not a btree index",
                 RelationGetRelationName(rel));

        /*
         * Reject attempts to read non-local temporary relations; we would be
         * likely to get wrong data since we have no visibility into the
         * owning session's local buffers.
         */
        if (RELATION_IS_OTHER_TEMP(rel))
            ereport(ERROR,
                    (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                     errmsg("cannot access temporary tables of other sessions")));

        if (blkno == 0)
            elog(ERROR, "block 0 is a meta page");

        CHECK_RELATION_BLOCK_RANGE(rel, blkno);

        buffer = ReadBuffer(rel, blkno);
        LockBuffer(buffer, BUFFER_LOCK_SHARE);

        /*
         * We copy the page into local storage to avoid holding pin on the
         * buffer longer than we must, and possibly failing to release it at
         * all if the calling query doesn't fetch all rows.
         */
        mctx = MemoryContextSwitchTo(fctx->multi_call_memory_ctx);

        uargs = palloc(sizeof(struct user_args));

        uargs->page = palloc(BLCKSZ);
        memcpy(uargs->page, BufferGetPage(buffer), BLCKSZ);

        UnlockReleaseBuffer(buffer);
        relation_close(rel, AccessShareLock);

        uargs->offset = FirstOffsetNumber;

        opaque = (BTPageOpaque) PageGetSpecialPointer(uargs->page);

        if (P_ISDELETED(opaque))
            elog(NOTICE, "page is deleted");

        fctx->max_calls = PageGetMaxOffsetNumber(uargs->page);

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

        fctx->attinmeta = TupleDescGetAttInMetadata(tupleDesc);

        fctx->user_fctx = uargs;

        MemoryContextSwitchTo(mctx);
    }

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

    if (fctx->call_cntr < fctx->max_calls)
    {
        result = bt_page_print_tuples(fctx, uargs->page, uargs->offset);
        uargs->offset++;
        SRF_RETURN_NEXT(fctx, result);
    }
    else
    {
        pfree(uargs->page);
        pfree(uargs);
        SRF_RETURN_DONE(fctx);
    }
}

/*-------------------------------------------------------
 * bt_page_items_bytea()
 *
 * Get IndexTupleData set in a btree page
 *
 * Usage: SELECT * FROM bt_page_items(get_raw_page('t1_pkey', 1));
 *-------------------------------------------------------
 */

Datum
bt_page_items_bytea(PG_FUNCTION_ARGS)
{
    bytea      *raw_page = PG_GETARG_BYTEA_P(0);
    Datum       result;
    FuncCallContext *fctx;
    struct user_args *uargs;
    int         raw_page_size;

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

    if (SRF_IS_FIRSTCALL())
    {
        BTPageOpaque opaque;
        MemoryContext mctx;
        TupleDesc   tupleDesc;

        raw_page_size = VARSIZE(raw_page) - VARHDRSZ;

        if (raw_page_size < SizeOfPageHeaderData)
            ereport(ERROR,
                    (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                     errmsg("input page too small (%d bytes)", raw_page_size)));

        fctx = SRF_FIRSTCALL_INIT();
        mctx = MemoryContextSwitchTo(fctx->multi_call_memory_ctx);

        uargs = palloc(sizeof(struct user_args));

        uargs->page = VARDATA(raw_page);

        uargs->offset = FirstOffsetNumber;

        opaque = (BTPageOpaque) PageGetSpecialPointer(uargs->page);

        if (P_ISMETA(opaque))
            ereport(ERROR,
                    (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                     errmsg("block is a meta page")));

        if (P_ISDELETED(opaque))
            elog(NOTICE, "page is deleted");

        fctx->max_calls = PageGetMaxOffsetNumber(uargs->page);

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

        fctx->attinmeta = TupleDescGetAttInMetadata(tupleDesc);

        fctx->user_fctx = uargs;

        MemoryContextSwitchTo(mctx);
    }

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

    if (fctx->call_cntr < fctx->max_calls)
    {
        result = bt_page_print_tuples(fctx, uargs->page, uargs->offset);
        uargs->offset++;
        SRF_RETURN_NEXT(fctx, result);
    }
    else
    {
        pfree(uargs);
        SRF_RETURN_DONE(fctx);
    }
}


/* ------------------------------------------------
 * bt_metap()
 *
 * Get a btree's meta-page information
 *
 * Usage: SELECT * FROM bt_metap('t1_pkey')
 * ------------------------------------------------
 */
Datum
bt_metap(PG_FUNCTION_ARGS)
{
    text       *relname = PG_GETARG_TEXT_PP(0);
    Datum       result;
    Relation    rel;
    RangeVar   *relrv;
    BTMetaPageData *metad;
    TupleDesc   tupleDesc;
    int         j;
    char       *values[6];
    Buffer      buffer;
    Page        page;
    HeapTuple   tuple;

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

    relrv = makeRangeVarFromNameList(textToQualifiedNameList(relname));
    rel = relation_openrv(relrv, AccessShareLock);

    if (!IS_INDEX(rel) || !IS_BTREE(rel))
        elog(ERROR, "relation \"%s\" is not a btree index",
             RelationGetRelationName(rel));

    /*
     * Reject attempts to read non-local temporary relations; we would be
     * likely to get wrong data since we have no visibility into the owning
     * session's local buffers.
     */
    if (RELATION_IS_OTHER_TEMP(rel))
        ereport(ERROR,
                (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                 errmsg("cannot access temporary tables of other sessions")));

    buffer = ReadBuffer(rel, 0);
    LockBuffer(buffer, BUFFER_LOCK_SHARE);

    page = BufferGetPage(buffer);
    metad = BTPageGetMeta(page);

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

    j = 0;
    values[j++] = psprintf("%d", metad->btm_magic);
    values[j++] = psprintf("%d", metad->btm_version);
    values[j++] = psprintf("%d", metad->btm_root);
    values[j++] = psprintf("%d", metad->btm_level);
    values[j++] = psprintf("%d", metad->btm_fastroot);
    values[j++] = psprintf("%d", metad->btm_fastlevel);

    tuple = BuildTupleFromCStrings(TupleDescGetAttInMetadata(tupleDesc),
                                   values);

    result = HeapTupleGetDatum(tuple);

    UnlockReleaseBuffer(buffer);
    relation_close(rel, AccessShareLock);

    PG_RETURN_DATUM(result);
}