ginfuncs.c

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/*
 * ginfuncs.c
 *      Functions to investigate the content of GIN indexes
 *
 * Copyright (c) 2014-2021, PostgreSQL Global Development Group
 *
 * IDENTIFICATION
 *      contrib/pageinspect/ginfuncs.c
 */
#include "postgres.h"

#include "access/gin.h"
#include "access/gin_private.h"
#include "access/htup_details.h"
#include "catalog/namespace.h"
#include "catalog/pg_type.h"
#include "funcapi.h"
#include "miscadmin.h"
#include "pageinspect.h"
#include "utils/array.h"
#include "utils/builtins.h"
#include "utils/rel.h"

#define DatumGetItemPointer(X)   ((ItemPointer) DatumGetPointer(X))
#define ItemPointerGetDatum(X)   PointerGetDatum(X)


PG_FUNCTION_INFO_V1(gin_metapage_info);
PG_FUNCTION_INFO_V1(gin_page_opaque_info);
PG_FUNCTION_INFO_V1(gin_leafpage_items);


Datum
gin_metapage_info(PG_FUNCTION_ARGS)
{
    bytea      *raw_page = PG_GETARG_BYTEA_P(0);
    TupleDesc   tupdesc;
    Page        page;
    GinPageOpaque opaq;
    GinMetaPageData *metadata;
    HeapTuple   resultTuple;
    Datum       values[10];
    bool        nulls[10];

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

    page = get_page_from_raw(raw_page);

    opaq = (GinPageOpaque) PageGetSpecialPointer(page);
    if (opaq->flags != GIN_META)
        ereport(ERROR,
                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                 errmsg("input page is not a GIN metapage"),
                 errdetail("Flags %04X, expected %04X",
                           opaq->flags, GIN_META)));

    /* 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");

    metadata = GinPageGetMeta(page);

    memset(nulls, 0, sizeof(nulls));

    values[0] = Int64GetDatum(metadata->head);
    values[1] = Int64GetDatum(metadata->tail);
    values[2] = Int32GetDatum(metadata->tailFreeSize);
    values[3] = Int64GetDatum(metadata->nPendingPages);
    values[4] = Int64GetDatum(metadata->nPendingHeapTuples);

    /* statistics, updated by VACUUM */
    values[5] = Int64GetDatum(metadata->nTotalPages);
    values[6] = Int64GetDatum(metadata->nEntryPages);
    values[7] = Int64GetDatum(metadata->nDataPages);
    values[8] = Int64GetDatum(metadata->nEntries);

    values[9] = Int32GetDatum(metadata->ginVersion);

    /* Build and return the result tuple. */
    resultTuple = heap_form_tuple(tupdesc, values, nulls);

    return HeapTupleGetDatum(resultTuple);
}


Datum
gin_page_opaque_info(PG_FUNCTION_ARGS)
{
    bytea      *raw_page = PG_GETARG_BYTEA_P(0);
    TupleDesc   tupdesc;
    Page        page;
    GinPageOpaque opaq;
    HeapTuple   resultTuple;
    Datum       values[3];
    bool        nulls[3];
    Datum       flags[16];
    int         nflags = 0;
    uint16      flagbits;

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

    page = get_page_from_raw(raw_page);

    opaq = (GinPageOpaque) PageGetSpecialPointer(page);

    /* 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");

    /* Convert the flags bitmask to an array of human-readable names */
    flagbits = opaq->flags;
    if (flagbits & GIN_DATA)
        flags[nflags++] = CStringGetTextDatum("data");
    if (flagbits & GIN_LEAF)
        flags[nflags++] = CStringGetTextDatum("leaf");
    if (flagbits & GIN_DELETED)
        flags[nflags++] = CStringGetTextDatum("deleted");
    if (flagbits & GIN_META)
        flags[nflags++] = CStringGetTextDatum("meta");
    if (flagbits & GIN_LIST)
        flags[nflags++] = CStringGetTextDatum("list");
    if (flagbits & GIN_LIST_FULLROW)
        flags[nflags++] = CStringGetTextDatum("list_fullrow");
    if (flagbits & GIN_INCOMPLETE_SPLIT)
        flags[nflags++] = CStringGetTextDatum("incomplete_split");
    if (flagbits & GIN_COMPRESSED)
        flags[nflags++] = CStringGetTextDatum("compressed");
    flagbits &= ~(GIN_DATA | GIN_LEAF | GIN_DELETED | GIN_META | GIN_LIST |
                  GIN_LIST_FULLROW | GIN_INCOMPLETE_SPLIT | GIN_COMPRESSED);
    if (flagbits)
    {
        /* any flags we don't recognize are printed in hex */
        flags[nflags++] = DirectFunctionCall1(to_hex32, Int32GetDatum(flagbits));
    }

    memset(nulls, 0, sizeof(nulls));

    values[0] = Int64GetDatum(opaq->rightlink);
    values[1] = Int32GetDatum(opaq->maxoff);
    values[2] = PointerGetDatum(construct_array(flags, nflags,
                                                TEXTOID,
                                                -1, false, TYPALIGN_INT));

    /* Build and return the result tuple. */
    resultTuple = heap_form_tuple(tupdesc, values, nulls);

    return HeapTupleGetDatum(resultTuple);
}

typedef struct gin_leafpage_items_state
{
    TupleDesc   tupd;
    GinPostingList *seg;
    GinPostingList *lastseg;
} gin_leafpage_items_state;

Datum
gin_leafpage_items(PG_FUNCTION_ARGS)
{
    bytea      *raw_page = PG_GETARG_BYTEA_P(0);
    FuncCallContext *fctx;
    gin_leafpage_items_state *inter_call_data;

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

    if (SRF_IS_FIRSTCALL())
    {
        TupleDesc   tupdesc;
        MemoryContext mctx;
        Page        page;
        GinPageOpaque opaq;

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

        page = get_page_from_raw(raw_page);

        if (PageGetSpecialSize(page) != MAXALIGN(sizeof(GinPageOpaqueData)))
            ereport(ERROR,
                    (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                     errmsg("input page is not a valid GIN data leaf page"),
                     errdetail("Special size %d, expected %d",
                               (int) PageGetSpecialSize(page),
                               (int) MAXALIGN(sizeof(GinPageOpaqueData)))));

        opaq = (GinPageOpaque) PageGetSpecialPointer(page);
        if (opaq->flags != (GIN_DATA | GIN_LEAF | GIN_COMPRESSED))
            ereport(ERROR,
                    (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                     errmsg("input page is not a compressed GIN data leaf page"),
                     errdetail("Flags %04X, expected %04X",
                               opaq->flags,
                               (GIN_DATA | GIN_LEAF | GIN_COMPRESSED))));

        inter_call_data = palloc(sizeof(gin_leafpage_items_state));

        /* 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");

        inter_call_data->tupd = tupdesc;

        inter_call_data->seg = GinDataLeafPageGetPostingList(page);
        inter_call_data->lastseg = (GinPostingList *)
            (((char *) inter_call_data->seg) +
             GinDataLeafPageGetPostingListSize(page));

        fctx->user_fctx = inter_call_data;

        MemoryContextSwitchTo(mctx);
    }

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

    if (inter_call_data->seg != inter_call_data->lastseg)
    {
        GinPostingList *cur = inter_call_data->seg;
        HeapTuple   resultTuple;
        Datum       result;
        Datum       values[3];
        bool        nulls[3];
        int         ndecoded,
                    i;
        ItemPointer tids;
        Datum      *tids_datum;

        memset(nulls, 0, sizeof(nulls));

        values[0] = ItemPointerGetDatum(&cur->first);
        values[1] = UInt16GetDatum(cur->nbytes);

        /* build an array of decoded item pointers */
        tids = ginPostingListDecode(cur, &ndecoded);
        tids_datum = (Datum *) palloc(ndecoded * sizeof(Datum));
        for (i = 0; i < ndecoded; i++)
            tids_datum[i] = ItemPointerGetDatum(&tids[i]);
        values[2] = PointerGetDatum(construct_array(tids_datum,
                                                    ndecoded,
                                                    TIDOID,
                                                    sizeof(ItemPointerData),
                                                    false, TYPALIGN_SHORT));
        pfree(tids_datum);
        pfree(tids);

        /* Build and return the result tuple. */
        resultTuple = heap_form_tuple(inter_call_data->tupd, values, nulls);
        result = HeapTupleGetDatum(resultTuple);

        inter_call_data->seg = GinNextPostingListSegment(cur);

        SRF_RETURN_NEXT(fctx, result);
    }

    SRF_RETURN_DONE(fctx);
}