buf_table.c File Reference

#include "postgres.h"
#include "storage/buf_internals.h"
#include "storage/subsystems.h"

Include dependency graph for buf_table.c:

Go to the source code of this file.

Data Structures
struct	BufferLookupEnt

Functions
static void	BufTableShmemRequest (void *arg)
uint32	BufTableHashCode (BufferTag *tagPtr)
int	BufTableLookup (BufferTag *tagPtr, uint32 hashcode)
int	BufTableInsert (BufferTag *tagPtr, uint32 hashcode, int buf_id)
void	BufTableDelete (BufferTag *tagPtr, uint32 hashcode)

Variables
static HTAB *	SharedBufHash
const ShmemCallbacks	BufTableShmemCallbacks

Function Documentation

BufTableDelete()

void BufTableDelete	(	BufferTag *	tagPtr,
		uint32	hashcode
	)

Definition at line 154 of file buf_table.c.

{
    BufferLookupEnt *result;
 
    result = (BufferLookupEnt *)
        hash_search_with_hash_value(SharedBufHash,
                                    tagPtr,
                                    hashcode,
                                    HASH_REMOVE,
                                    NULL);
 
    if (!result)                /* shouldn't happen */
        elog(ERROR, "shared buffer hash table corrupted");
}

References elog, ERROR, fb(), HASH_REMOVE, hash_search_with_hash_value(), result, and SharedBufHash.

Referenced by InvalidateBuffer(), and InvalidateVictimBuffer().

BufTableHashCode()

uint32 BufTableHashCode

(

BufferTag *

tagPtr

)

Definition at line 84 of file buf_table.c.

{
    return get_hash_value(SharedBufHash, tagPtr);
}

References fb(), get_hash_value(), and SharedBufHash.

Referenced by BufferAlloc(), ExtendBufferedRelShared(), FindAndDropRelationBuffers(), InvalidateBuffer(), InvalidateVictimBuffer(), and PrefetchSharedBuffer().

BufTableInsert()

int BufTableInsert	(	BufferTag *	tagPtr,
		uint32	hashcode,
		int	buf_id
	)

Definition at line 124 of file buf_table.c.

{
    BufferLookupEnt *result;
    bool        found;
 
    Assert(buf_id >= 0);        /* -1 is reserved for not-in-table */
    Assert(tagPtr->blockNum != P_NEW);  /* invalid tag */
 
    result = (BufferLookupEnt *)
        hash_search_with_hash_value(SharedBufHash,
                                    tagPtr,
                                    hashcode,
                                    HASH_ENTER,
                                    &found);
 
    if (found)                  /* found something already in the table */
        return result->id;
 
    result->id = buf_id;
 
    return -1;
}

References Assert, fb(), HASH_ENTER, hash_search_with_hash_value(), P_NEW, result, and SharedBufHash.

Referenced by BufferAlloc(), and ExtendBufferedRelShared().

BufTableLookup()

int BufTableLookup	(	BufferTag *	tagPtr,
		uint32	hashcode
	)

Definition at line 96 of file buf_table.c.

{
    BufferLookupEnt *result;
 
    result = (BufferLookupEnt *)
        hash_search_with_hash_value(SharedBufHash,
                                    tagPtr,
                                    hashcode,
                                    HASH_FIND,
                                    NULL);
 
    if (!result)
        return -1;
 
    return result->id;
}

References fb(), HASH_FIND, hash_search_with_hash_value(), BufferLookupEnt::id, result, and SharedBufHash.

Referenced by BufferAlloc(), FindAndDropRelationBuffers(), and PrefetchSharedBuffer().

BufTableShmemRequest()

void BufTableShmemRequest ( void *  arg )

static

Definition at line 48 of file buf_table.c.

{
    int         size;
 
    /*
     * Request the shared buffer lookup hashtable.
     *
     * Since we can't tolerate running out of lookup table entries, we must be
     * sure to specify an adequate table size here.  The maximum steady-state
     * usage is of course NBuffers entries, but BufferAlloc() tries to insert
     * a new entry before deleting the old.  In principle this could be
     * happening in each partition concurrently, so we could need as many as
     * NBuffers + NUM_BUFFER_PARTITIONS entries.
     */
    size = NBuffers + NUM_BUFFER_PARTITIONS;
 
    ShmemRequestHash(.name = "Shared Buffer Lookup Table",
                     .nelems = size,
                     .ptr = &SharedBufHash,
                     .hash_info.keysize = sizeof(BufferTag),
                     .hash_info.entrysize = sizeof(BufferLookupEnt),
                     .hash_info.num_partitions = NUM_BUFFER_PARTITIONS,
                     .hash_flags = HASH_ELEM | HASH_BLOBS | HASH_PARTITION | HASH_FIXED_SIZE,
        );
}

References HASH_BLOBS, HASH_ELEM, HASH_FIXED_SIZE, HASH_PARTITION, HTAB::keysize, name, NBuffers, NUM_BUFFER_PARTITIONS, SharedBufHash, and ShmemRequestHash.

Variable Documentation

BufTableShmemCallbacks

const ShmemCallbacks BufTableShmemCallbacks

Initial value:

= {
    .request_fn = BufTableShmemRequest,
    
}

Definition at line 38 of file buf_table.c.

                                              {
    .request_fn = BufTableShmemRequest,
    /* no special initialization needed, the hash table will start empty */
};

SharedBufHash

HTAB* SharedBufHash

static

Definition at line 34 of file buf_table.c.

Referenced by BufTableDelete(), BufTableHashCode(), BufTableInsert(), BufTableLookup(), and BufTableShmemRequest().