time_mapping.c File Reference

#include "postgres.h"
#include "funcapi.h"
#include "storage/lwlock.h"
#include "utils/old_snapshot.h"
#include "utils/snapmgr.h"
#include "utils/timestamp.h"

Include dependency graph for time_mapping.c:

Go to the source code of this file.

Data Structures
struct	OldSnapshotTimeMapping

Macros
#define	NUM_TIME_MAPPING_COLUMNS   3

Functions
	PG_FUNCTION_INFO_V1 (pg_old_snapshot_time_mapping)
static OldSnapshotTimeMapping *	GetOldSnapshotTimeMapping (void)
static TupleDesc	MakeOldSnapshotTimeMappingTupleDesc (void)
static HeapTuple	MakeOldSnapshotTimeMappingTuple (TupleDesc tupdesc, OldSnapshotTimeMapping *mapping)
Datum	pg_old_snapshot_time_mapping (PG_FUNCTION_ARGS)

Variables
	PG_MODULE_MAGIC

Macro Definition Documentation

NUM_TIME_MAPPING_COLUMNS

#define NUM_TIME_MAPPING_COLUMNS   3

Definition at line 35 of file time_mapping.c.

Referenced by MakeOldSnapshotTimeMappingTuple(), and MakeOldSnapshotTimeMappingTupleDesc().

Function Documentation

GetOldSnapshotTimeMapping()

static OldSnapshotTimeMapping * GetOldSnapshotTimeMapping ( void  )

static

Definition at line 85 of file time_mapping.c.

References OldSnapshotTimeMapping::count_used, OldSnapshotControlData::count_used, OldSnapshotTimeMapping::current_index, OldSnapshotTimeMapping::head_offset, OldSnapshotControlData::head_offset, OldSnapshotTimeMapping::head_timestamp, OldSnapshotControlData::head_timestamp, i, LW_SHARED, LWLockAcquire(), LWLockRelease(), offsetof, OLD_SNAPSHOT_TIME_MAP_ENTRIES, oldSnapshotControl, palloc(), OldSnapshotTimeMapping::xid_by_minute, and OldSnapshotControlData::xid_by_minute.

Referenced by pg_old_snapshot_time_mapping().

{
    OldSnapshotTimeMapping *mapping;

    mapping = palloc(offsetof(OldSnapshotTimeMapping, xid_by_minute)
                     + sizeof(TransactionId) * OLD_SNAPSHOT_TIME_MAP_ENTRIES);
    mapping->current_index = 0;

    LWLockAcquire(OldSnapshotTimeMapLock, LW_SHARED);
    mapping->head_offset = oldSnapshotControl->head_offset;
    mapping->head_timestamp = oldSnapshotControl->head_timestamp;
    mapping->count_used = oldSnapshotControl->count_used;
    for (int i = 0; i < OLD_SNAPSHOT_TIME_MAP_ENTRIES; ++i)
        mapping->xid_by_minute[i] = oldSnapshotControl->xid_by_minute[i];
    LWLockRelease(OldSnapshotTimeMapLock);

    return mapping;
}

MakeOldSnapshotTimeMappingTuple()

static HeapTuple MakeOldSnapshotTimeMappingTuple ( TupleDesc  tupdesc, OldSnapshotTimeMapping *  mapping  )

static

Definition at line 128 of file time_mapping.c.

References array_position(), OldSnapshotTimeMapping::current_index, OldSnapshotTimeMapping::head_offset, OldSnapshotTimeMapping::head_timestamp, heap_form_tuple(), Int32GetDatum, NUM_TIME_MAPPING_COLUMNS, OLD_SNAPSHOT_TIME_MAP_ENTRIES, TimestampTzGetDatum, TimestampTzPlusMilliseconds, TransactionIdGetDatum, values, and OldSnapshotTimeMapping::xid_by_minute.

Referenced by pg_old_snapshot_time_mapping().

{
    Datum   values[NUM_TIME_MAPPING_COLUMNS];
    bool    nulls[NUM_TIME_MAPPING_COLUMNS];
    int     array_position;
    TimestampTz timestamp;

    /*
     * Figure out the array position corresponding to the current index.
     *
     * Index 0 means the oldest entry in the mapping, which is stored at
     * mapping->head_offset. Index 1 means the next-oldest entry, which is a the
     * following index, and so on. We wrap around when we reach the end of the array.
     */
    array_position = (mapping->head_offset + mapping->current_index)
        % OLD_SNAPSHOT_TIME_MAP_ENTRIES;

    /*
     * No explicit timestamp is stored for any entry other than the oldest one,
     * but each entry corresponds to 1-minute period, so we can just add.
     */
    timestamp = TimestampTzPlusMilliseconds(mapping->head_timestamp,
                                            mapping->current_index * 60000);

    /* Initialize nulls and values arrays. */
    memset(nulls, 0, sizeof(nulls));
    values[0] = Int32GetDatum(array_position);
    values[1] = TimestampTzGetDatum(timestamp);
    values[2] = TransactionIdGetDatum(mapping->xid_by_minute[array_position]);

    return heap_form_tuple(tupdesc, values, nulls);
}

MakeOldSnapshotTimeMappingTupleDesc()

static TupleDesc MakeOldSnapshotTimeMappingTupleDesc ( void  )

static

Definition at line 108 of file time_mapping.c.

References BlessTupleDesc(), CreateTemplateTupleDesc(), NUM_TIME_MAPPING_COLUMNS, and TupleDescInitEntry().

Referenced by pg_old_snapshot_time_mapping().

{
    TupleDesc   tupdesc;

    tupdesc = CreateTemplateTupleDesc(NUM_TIME_MAPPING_COLUMNS);

    TupleDescInitEntry(tupdesc, (AttrNumber) 1, "array_offset",
                       INT4OID, -1, 0);
    TupleDescInitEntry(tupdesc, (AttrNumber) 2, "end_timestamp",
                       TIMESTAMPTZOID, -1, 0);
    TupleDescInitEntry(tupdesc, (AttrNumber) 3, "newest_xmin",
                       XIDOID, -1, 0);

    return BlessTupleDesc(tupdesc);
}

PG_FUNCTION_INFO_V1()

PG_FUNCTION_INFO_V1

(

pg_old_snapshot_time_mapping

)

pg_old_snapshot_time_mapping()

Datum pg_old_snapshot_time_mapping

(

PG_FUNCTION_ARGS

)

Definition at line 49 of file time_mapping.c.

References OldSnapshotTimeMapping::count_used, OldSnapshotTimeMapping::current_index, GetOldSnapshotTimeMapping(), HeapTupleGetDatum, MakeOldSnapshotTimeMappingTuple(), MakeOldSnapshotTimeMappingTupleDesc(), MemoryContextSwitchTo(), FuncCallContext::multi_call_memory_ctx, SRF_FIRSTCALL_INIT, SRF_IS_FIRSTCALL, SRF_PERCALL_SETUP, SRF_RETURN_DONE, SRF_RETURN_NEXT, FuncCallContext::tuple_desc, and FuncCallContext::user_fctx.

{
    FuncCallContext *funcctx;
    OldSnapshotTimeMapping *mapping;

    if (SRF_IS_FIRSTCALL())
    {
        MemoryContext   oldcontext;

        funcctx = SRF_FIRSTCALL_INIT();
        oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);
        mapping = GetOldSnapshotTimeMapping();
        funcctx->user_fctx = mapping;
        funcctx->tuple_desc = MakeOldSnapshotTimeMappingTupleDesc();
        MemoryContextSwitchTo(oldcontext);
    }

    funcctx = SRF_PERCALL_SETUP();
    mapping = (OldSnapshotTimeMapping *) funcctx->user_fctx;

    while (mapping->current_index < mapping->count_used)
    {
        HeapTuple   tuple;

        tuple = MakeOldSnapshotTimeMappingTuple(funcctx->tuple_desc, mapping);
        ++mapping->current_index;
        SRF_RETURN_NEXT(funcctx, HeapTupleGetDatum(tuple));
    }

    SRF_RETURN_DONE(funcctx);
}

Variable Documentation

PG_MODULE_MAGIC

PG_MODULE_MAGIC

Definition at line 37 of file time_mapping.c.