ginbulk.c

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/*-------------------------------------------------------------------------
 *
 * ginbulk.c
 *    routines for fast build of inverted index
 *
 *
 * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * IDENTIFICATION
 *          src/backend/access/gin/ginbulk.c
 *-------------------------------------------------------------------------
 */
 
#include "postgres.h"
 
#include <limits.h>
 
#include "access/gin_private.h"
#include "utils/datum.h"
#include "utils/memutils.h"
 
 
#define DEF_NENTRY  2048        /* GinEntryAccumulator allocation quantum */
#define DEF_NPTR    5           /* ItemPointer initial allocation quantum */
 
 
/* Combiner function for rbtree.c */
static void
ginCombineData(RBTNode *existing, const RBTNode *newdata, void *arg)
{
    GinEntryAccumulator *eo = (GinEntryAccumulator *) existing;
    const GinEntryAccumulator *en = (const GinEntryAccumulator *) newdata;
    BuildAccumulator *accum = (BuildAccumulator *) arg;
 
    /*
     * Note this code assumes that newdata contains only one itempointer.
     */
    if (eo->count >= eo->maxcount)
    {
        if (eo->maxcount > INT_MAX)
            ereport(ERROR,
                    (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
                     errmsg("posting list is too long"),
                     errhint("Reduce \"maintenance_work_mem\".")));
 
        accum->allocatedMemory -= GetMemoryChunkSpace(eo->list);
        eo->maxcount *= 2;
        eo->list = (ItemPointerData *)
            repalloc_huge(eo->list, sizeof(ItemPointerData) * eo->maxcount);
        accum->allocatedMemory += GetMemoryChunkSpace(eo->list);
    }
 
    /* If item pointers are not ordered, they will need to be sorted later */
    if (eo->shouldSort == false)
    {
        int         res;
 
        res = ginCompareItemPointers(eo->list + eo->count - 1, en->list);
        Assert(res != 0);
 
        if (res > 0)
            eo->shouldSort = true;
    }
 
    eo->list[eo->count] = en->list[0];
    eo->count++;
}
 
/* Comparator function for rbtree.c */
static int
cmpEntryAccumulator(const RBTNode *a, const RBTNode *b, void *arg)
{
    const GinEntryAccumulator *ea = (const GinEntryAccumulator *) a;
    const GinEntryAccumulator *eb = (const GinEntryAccumulator *) b;
    BuildAccumulator *accum = (BuildAccumulator *) arg;
 
    return ginCompareAttEntries(accum->ginstate,
                                ea->attnum, ea->key, ea->category,
                                eb->attnum, eb->key, eb->category);
}
 
/* Allocator function for rbtree.c */
static RBTNode *
ginAllocEntryAccumulator(void *arg)
{
    BuildAccumulator *accum = (BuildAccumulator *) arg;
    GinEntryAccumulator *ea;
 
    /*
     * Allocate memory by rather big chunks to decrease overhead.  We have no
     * need to reclaim RBTNodes individually, so this costs nothing.
     */
    if (accum->entryallocator == NULL || accum->eas_used >= DEF_NENTRY)
    {
        accum->entryallocator = palloc(sizeof(GinEntryAccumulator) * DEF_NENTRY);
        accum->allocatedMemory += GetMemoryChunkSpace(accum->entryallocator);
        accum->eas_used = 0;
    }
 
    /* Allocate new RBTNode from current chunk */
    ea = accum->entryallocator + accum->eas_used;
    accum->eas_used++;
 
    return (RBTNode *) ea;
}
 
void
ginInitBA(BuildAccumulator *accum)
{
    /* accum->ginstate is intentionally not set here */
    accum->allocatedMemory = 0;
    accum->entryallocator = NULL;
    accum->eas_used = 0;
    accum->tree = rbt_create(sizeof(GinEntryAccumulator),
                             cmpEntryAccumulator,
                             ginCombineData,
                             ginAllocEntryAccumulator,
                             NULL,  /* no freefunc needed */
                             accum);
}
 
/*
 * This is basically the same as datumCopy(), but extended to count
 * palloc'd space in accum->allocatedMemory.
 */
static Datum
getDatumCopy(BuildAccumulator *accum, OffsetNumber attnum, Datum value)
{
    CompactAttribute *att;
    Datum       res;
 
    att = TupleDescCompactAttr(accum->ginstate->origTupdesc, attnum - 1);
    if (att->attbyval)
        res = value;
    else
    {
        res = datumCopy(value, false, att->attlen);
        accum->allocatedMemory += GetMemoryChunkSpace(DatumGetPointer(res));
    }
    return res;
}
 
/*
 * Find/store one entry from indexed value.
 */
static void
ginInsertBAEntry(BuildAccumulator *accum,
                 ItemPointer heapptr, OffsetNumber attnum,
                 Datum key, GinNullCategory category)
{
    GinEntryAccumulator eatmp;
    GinEntryAccumulator *ea;
    bool        isNew;
 
    /*
     * For the moment, fill only the fields of eatmp that will be looked at by
     * cmpEntryAccumulator or ginCombineData.
     */
    eatmp.attnum = attnum;
    eatmp.key = key;
    eatmp.category = category;
    /* temporarily set up single-entry itempointer list */
    eatmp.list = heapptr;
 
    ea = (GinEntryAccumulator *) rbt_insert(accum->tree, (RBTNode *) &eatmp,
                                            &isNew);
 
    if (isNew)
    {
        /*
         * Finish initializing new tree entry, including making permanent
         * copies of the datum (if it's not null) and itempointer.
         */
        if (category == GIN_CAT_NORM_KEY)
            ea->key = getDatumCopy(accum, attnum, key);
        ea->maxcount = DEF_NPTR;
        ea->count = 1;
        ea->shouldSort = false;
        ea->list =
            (ItemPointerData *) palloc(sizeof(ItemPointerData) * DEF_NPTR);
        ea->list[0] = *heapptr;
        accum->allocatedMemory += GetMemoryChunkSpace(ea->list);
    }
    else
    {
        /*
         * ginCombineData did everything needed.
         */
    }
}
 
/*
 * Insert the entries for one heap pointer.
 *
 * Since the entries are being inserted into a balanced binary tree, you
 * might think that the order of insertion wouldn't be critical, but it turns
 * out that inserting the entries in sorted order results in a lot of
 * rebalancing operations and is slow.  To prevent this, we attempt to insert
 * the nodes in an order that will produce a nearly-balanced tree if the input
 * is in fact sorted.
 *
 * We do this as follows.  First, we imagine that we have an array whose size
 * is the smallest power of two greater than or equal to the actual array
 * size.  Second, we insert the middle entry of our virtual array into the
 * tree; then, we insert the middles of each half of our virtual array, then
 * middles of quarters, etc.
 */
void
ginInsertBAEntries(BuildAccumulator *accum,
                   ItemPointer heapptr, OffsetNumber attnum,
                   Datum *entries, GinNullCategory *categories,
                   int32 nentries)
{
    uint32      step = nentries;
 
    if (nentries <= 0)
        return;
 
    Assert(ItemPointerIsValid(heapptr) && attnum >= FirstOffsetNumber);
 
    /*
     * step will contain largest power of 2 and <= nentries
     */
    step |= (step >> 1);
    step |= (step >> 2);
    step |= (step >> 4);
    step |= (step >> 8);
    step |= (step >> 16);
    step >>= 1;
    step++;
 
    while (step > 0)
    {
        int         i;
 
        for (i = step - 1; i < nentries && i >= 0; i += step << 1 /* *2 */ )
            ginInsertBAEntry(accum, heapptr, attnum,
                             entries[i], categories[i]);
 
        step >>= 1;             /* /2 */
    }
}
 
static int
qsortCompareItemPointers(const void *a, const void *b)
{
    int         res = ginCompareItemPointers((ItemPointer) a, (ItemPointer) b);
 
    /* Assert that there are no equal item pointers being sorted */
    Assert(res != 0);
    return res;
}
 
/* Prepare to read out the rbtree contents using ginGetBAEntry */
void
ginBeginBAScan(BuildAccumulator *accum)
{
    rbt_begin_iterate(accum->tree, LeftRightWalk, &accum->tree_walk);
}
 
/*
 * Get the next entry in sequence from the BuildAccumulator's rbtree.
 * This consists of a single key datum and a list (array) of one or more
 * heap TIDs in which that key is found.  The list is guaranteed sorted.
 */
ItemPointerData *
ginGetBAEntry(BuildAccumulator *accum,
              OffsetNumber *attnum, Datum *key, GinNullCategory *category,
              uint32 *n)
{
    GinEntryAccumulator *entry;
    ItemPointerData *list;
 
    entry = (GinEntryAccumulator *) rbt_iterate(&accum->tree_walk);
 
    if (entry == NULL)
        return NULL;            /* no more entries */
 
    *attnum = entry->attnum;
    *key = entry->key;
    *category = entry->category;
    list = entry->list;
    *n = entry->count;
 
    Assert(list != NULL && entry->count > 0);
 
    if (entry->shouldSort && entry->count > 1)
        qsort(list, entry->count, sizeof(ItemPointerData),
              qsortCompareItemPointers);
 
    return list;
}