PostgreSQL 源码解读（236）- 后台进程#14（autovacuum进程#2）

本节简单介绍了PostgreSQL的后台进程:autovacuum,主要分析了launch_worker函数的实现逻辑。

一、数据结构

AutoVacuumShmem
主要的autovacuum共享内存结构体,存储在shared memory中,同时WorkerInfo也会存储在其中.

/*------------- * The main autovacuum shmem struct.  On shared memory we store this main * struct and the array of WorkerInfo structs.  This struct keeps: * 主要的autovacuum共享内存结构体,存储在shared memory中,同时WorkerInfo也会存储在其中. * 该结构体包括: * * av_signal        set by other processes to indicate various conditions * 其他进程设置用于提示不同的条件 * av_launcherpid   the PID of the autovacuum launcher * autovacuum launcher的PID * av_freeWorkers   the WorkerInfo freelist * WorkerInfo空闲链表 * av_runningWorkers the WorkerInfo non-free queue * WorkerInfo非空闲队列 * av_startingWorker pointer to WorkerInfo currently being started (cleared by *                  the worker itself as soon as it's up and running) * av_startingWorker指向当前正在启动的WorkerInfo * av_workItems     work item array * av_workItems 工作条目数组 * * This struct is protected by AutovacuumLock, except for av_signal and parts * of the worker list (see above). * 除了av_signal和worker list的一部分信息，该数据结构通过AutovacuumLock保护 *------------- */typedef struct{    sig_atomic_t av_signal[AutoVacNumSignals];    pid_t       av_launcherpid;    dlist_head  av_freeWorkers;    dlist_head  av_runningWorkers;    WorkerInfo  av_startingWorker;    AutoVacuumWorkItem av_workItems[NUM_WORKITEMS];} AutoVacuumShmemStruct;static AutoVacuumShmemStruct *AutoVacuumShmem;

FullTransactionId
64 bit的事务ID

/* * A 64 bit value that contains an epoch and a TransactionId.  This is * wrapped in a struct to prevent implicit conversion to/from TransactionId. * Not all values represent valid normal XIDs. * 保护epoch和TransactionId的64 bit值.封装在结构体中避免与事务ID的隐式转换.并不是所有的值都表示有效的普通xid。 */typedef struct FullTransactionId{    uint64      value;} FullTransactionId;

avw_dbase
用于跟踪worker中的数据库的结构体

/* struct to keep track of databases in worker *///用于跟踪worker中的数据库的结构体typedef struct avw_dbase{    Oid         adw_datid;    char       *adw_name;    TransactionId adw_frozenxid;    MultiXactId adw_minmulti;    PgStat_StatDBEntry *adw_entry;} avw_dbase;

WorkerInfo

/* * Structure to hold info passed by _beginthreadex() to the function it calls * via its single allowed argument. */typedef struct{    ArchiveHandle *AH;          /* master database connection */    ParallelSlot *slot;         /* this worker's parallel slot */} WorkerInfo;

二、源码解读

主要的实现逻辑在do_start_worker中

/* * launch_worker * * Wrapper for starting a worker from the launcher.  Besides actually starting * it, update the database list to reflect the next time that another one will * need to be started on the selected database.  The actual database choice is * left to do_start_worker. * 从autovacuum launcher启动worker的封装器. * 除了实际启动它之外，还要更新数据库链表，以反映下一次需要在选定的数据库上启动另一个worker时的情况。 *   实际的数据库选择留给do_start_worker。 * * This routine is also expected to insert an entry into the database list if * the selected database was previously absent from the list. * 这段例程同样希望在数据库链表中插入一个新的条目,如果选定的数据库先前在链表中出现. */static voidlaunch_worker(TimestampTz now){    Oid         dbid;    dlist_iter  iter;    dbid = do_start_worker();    if (OidIsValid(dbid))    {        bool        found = false;        /*         * Walk the database list and update the corresponding entry.  If the         * database is not on the list, we'll recreate the list.         * 遍历数据库链表,更新相应的条目.         * 如果数据库不在链表链表中,重建链表.         */        dlist_foreach(iter, &DatabaseList)        {            avl_dbase  *avdb = dlist_container(avl_dbase, adl_node, iter.cur);            if (avdb->adl_datid == dbid)            {                found = true;                /*                 * add autovacuum_naptime seconds to the current time, and use                 * that as the new "next_worker" field for this database.                 * 在当前时间上增加autovacuum_naptime,                 *   并为该数据库使用该时间作为新的next_worker字段的值.                 */                avdb->adl_next_worker =                    TimestampTzPlusMilliseconds(now, autovacuum_naptime * 1000);                dlist_move_head(&DatabaseList, iter.cur);                break;            }        }        /*         * If the database was not present in the database list, we rebuild         * the list.  It's possible that the database does not get into the         * list anyway, for example if it's a database that doesn't have a         * pgstat entry, but this is not a problem because we don't want to         * schedule workers regularly into those in any case.         * 如果数据库不在数据库链表中,重建链表.         * 有可能该数据库没有进入过链表中,比如,该数据库没有pgstat条目入口,         *   但这不是一个问题,因为我们不希望在任何情况调度到这些数据库上面.         */        if (!found)            rebuild_database_list(dbid);    }}

do_start_worker
选择一个DB,算法如下:
选择最近最小清理的DB,或者需要清理以防止XID回卷导致数据丢失的DB.
如果存在XID回卷风险的DB,那么选择datfrozenxid最老的DB,而不管该DB做了多少次autovacuum.
自动忽略没有连接过(统计信息为空)的DB.

/* * do_start_worker * * Bare-bones procedure for starting an autovacuum worker from the launcher. * It determines what database to work on, sets up shared memory stuff and * signals postmaster to start the worker.  It fails gracefully if invoked when * autovacuum_workers are already active. * 启动autovacuum worker。 * 确定处理哪个库，配置共享内存并通知postmaster启动worker。 * 如autovacuum_workers已处于活动状态，则启动失败。 * * Return value is the OID of the database that the worker is going to process, * or InvalidOid if no worker was actually started. * 返回正在处理的数据库OID，如worker启动不成功，则返回InvalidOid。 */static Oiddo_start_worker(void){    List       *dblist;//数据库链表    ListCell   *cell;//临时变量    //typedef uint32 TransactionId;    TransactionId xidForceLimit;//事务id,无符号32bit整型    MultiXactId multiForceLimit;//    bool        for_xid_wrap;    bool        for_multi_wrap;    avw_dbase  *avdb;    TimestampTz current_time;//当前时间    bool        skipit = false;//是否跳过?    Oid         retval = InvalidOid;//返回的数据库OID    MemoryContext tmpcxt,                oldcxt;//内存上下文    /* return quickly when there are no free workers */    //如无空闲的worker(AutoVacuumShmem数据结构维护),则退出    LWLockAcquire(AutovacuumLock, LW_SHARED);    if (dlist_is_empty(&AutoVacuumShmem->av_freeWorkers))    {        LWLockRelease(AutovacuumLock);        return InvalidOid;    }    LWLockRelease(AutovacuumLock);    /*     * Create and switch to a temporary context to avoid leaking the memory     * allocated for the database list.     * 内存上下文切换     */    tmpcxt = AllocSetContextCreate(CurrentMemoryContext,                                   "Start worker tmp cxt",                                   ALLOCSET_DEFAULT_SIZES);    oldcxt = MemoryContextSwitchTo(tmpcxt);    /* use fresh stats */    //统计信息刷新    autovac_refresh_stats();    /* Get a list of databases */    //获取数据库链表    dblist = get_database_list();    /*     * Determine the oldest datfrozenxid/relfrozenxid that we will allow to     * pass without forcing a vacuum.  (This limit can be tightened for     * particular tables, but not loosened.)     * 确定最老的datfrozenxid/relfrozenxid,用以确定是否需要强制vacuum     */    recentXid = ReadNewTransactionId();    xidForceLimit = recentXid - autovacuum_freeze_max_age;    /* ensure it's a "normal" XID, else TransactionIdPrecedes misbehaves */    /* this can cause the limit to go backwards by 3, but that's OK */    //#define FirstNormalTransactionId  ((TransactionId) 3)    //小于3(常规的XID),则减去3    if (xidForceLimit < FirstNormalTransactionId)        xidForceLimit -= FirstNormalTransactionId;    /* Also determine the oldest datminmxid we will consider. */    //确定需要考虑的最老的datminmxid    //从MultiXactState->nextMXact中获取MultiXactId    recentMulti = ReadNextMultiXactId();    multiForceLimit = recentMulti - MultiXactMemberFreezeThreshold();    if (multiForceLimit < FirstMultiXactId)        multiForceLimit -= FirstMultiXactId;    /*     * Choose a database to connect to.  We pick the database that was least     * recently auto-vacuumed, or one that needs vacuuming to prevent Xid     * wraparound-related data loss.  If any db at risk of Xid wraparound is     * found, we pick the one with oldest datfrozenxid, independently of     * autovacuum times; similarly we pick the one with the oldest datminmxid     * if any is in MultiXactId wraparound.  Note that those in Xid wraparound     * danger are given more priority than those in multi wraparound danger.     *     * Note that a database with no stats entry is not considered, except for     * Xid wraparound purposes.  The theory is that if no one has ever     * connected to it since the stats were last initialized, it doesn't need     * vacuuming.     *     * XXX This could be improved if we had more info about whether it needs     * vacuuming before connecting to it.  Perhaps look through the pgstats     * data for the database's tables?  One idea is to keep track of the     * number of new and dead tuples per database in pgstats.  However it     * isn't clear how to construct a metric that measures that and not cause     * starvation for less busy databases.     * 选择一个DB.     * 算法:选择最近最小清理的DB,或者需要清理以防止XID回卷导致数据丢失的DB.     *      如果存在XID回卷风险的DB,那么选择datfrozenxid最老的DB,而不管该DB做了多少次autovacuum.     *      自动忽略没有连接过(统计信息为空)的DB.     */    avdb = NULL;//待清理的DB    for_xid_wrap = false;//xid回卷    for_multi_wrap = false;    current_time = GetCurrentTimestamp();//当前时间    foreach(cell, dblist)//循环db链表    {        avw_dbase  *tmp = lfirst(cell);        dlist_iter  iter;        /* Check to see if this one is at risk of wraparound */        //判断是否存在回卷风险?        //TransactionIdPrecedes --- is id1 logically < id2?        if (TransactionIdPrecedes(tmp->adw_frozenxid, xidForceLimit))        {            if (avdb == NULL ||                TransactionIdPrecedes(tmp->adw_frozenxid,                                      avdb->adw_frozenxid))                avdb = tmp;//选择较旧的那个            for_xid_wrap = true;            continue;        }        else if (for_xid_wrap)            continue;           /* ignore not-at-risk DBs */        else if (MultiXactIdPrecedes(tmp->adw_minmulti, multiForceLimit))        {            if (avdb == NULL ||                MultiXactIdPrecedes(tmp->adw_minmulti, avdb->adw_minmulti))                avdb = tmp;            for_multi_wrap = true;            continue;        }        else if (for_multi_wrap)            continue;           /* ignore not-at-risk DBs */        /* Find pgstat entry if any */        tmp->adw_entry = pgstat_fetch_stat_dbentry(tmp->adw_datid);        /*         * Skip a database with no pgstat entry; it means it hasn't seen any         * activity.         * 如无统计信息,跳过         */        if (!tmp->adw_entry)            continue;        /*         * Also, skip a database that appears on the database list as having         * been processed recently (less than autovacuum_naptime seconds ago).         * We do this so that we don't select a database which we just         * selected, but that pgstat hasn't gotten around to updating the last         * autovacuum time yet.         * 跳过出现在数据库链表中已处理过的DB(先前小于autovacuum_naptime秒)         * 执行该操作是为了避免选择刚才才选择的DB         */        skipit = false;        dlist_reverse_foreach(iter, &DatabaseList)        {            avl_dbase  *dbp = dlist_container(avl_dbase, adl_node, iter.cur);            if (dbp->adl_datid == tmp->adw_datid)            {                /*                 * Skip this database if its next_worker value falls between                 * the current time and the current time plus naptime.                 * 未超过时(naptime定义)                 */                if (!TimestampDifferenceExceeds(dbp->adl_next_worker,                                                current_time, 0) &&                    !TimestampDifferenceExceeds(current_time,                                                dbp->adl_next_worker,                                                autovacuum_naptime * 1000))                    skipit = true;                break;            }        }        if (skipit)            continue;        /*         * Remember the db with oldest autovac time.  (If we are here, both         * tmp->entry and db->entry must be non-null.)         */        if (avdb == NULL ||            tmp->adw_entry->last_autovac_time < avdb->adw_entry->last_autovac_time)            avdb = tmp;    }    /* Found a database -- process it */    if (avdb != NULL)    {        WorkerInfo  worker;        dlist_node *wptr;        LWLockAcquire(AutovacuumLock, LW_EXCLUSIVE);        /*         * Get a worker entry from the freelist.  We checked above, so there         * really should be a free slot.         * 从空闲链表中获取一个worker         */        wptr = dlist_pop_head_node(&AutoVacuumShmem->av_freeWorkers);        worker = dlist_container(WorkerInfoData, wi_links, wptr);        worker->wi_dboid = avdb->adw_datid;        worker->wi_proc = NULL;        worker->wi_launchtime = GetCurrentTimestamp();        AutoVacuumShmem->av_startingWorker = worker;        LWLockRelease(AutovacuumLock);        SendPostmasterSignal(PMSIGNAL_START_AUTOVAC_WORKER);        retval = avdb->adw_datid;    }    else if (skipit)    {        /*         * If we skipped all databases on the list, rebuild it, because it         * probably contains a dropped database.         */        rebuild_database_list(InvalidOid);    }    MemoryContextSwitchTo(oldcxt);    MemoryContextDelete(tmpcxt);    return retval;}/* * For callers that just need the XID part of the next transaction ID. */static inline TransactionIdReadNewTransactionId(void){    return XidFromFullTransactionId(ReadNextFullTransactionId());}#define XidFromFullTransactionId(x)     ((uint32) (x).value)/* * Read nextFullXid but don't allocate it. */FullTransactionIdReadNextFullTransactionId(void){    FullTransactionId fullXid;    LWLockAcquire(XidGenLock, LW_SHARED);    fullXid = ShmemVariableCache->nextFullXid;    LWLockRelease(XidGenLock);    return fullXid;}

三、跟踪分析

启动gdb,设置信号处理,设置断点

(gdb) handle SIGINT print nostop passSIGINT is used by the debugger.Are you sure you want to change it? (y or n) Please answer y or n.SIGINT is used by the debugger.Are you sure you want to change it? (y or n) ySignal        Stop  Print   Pass to program DescriptionSIGINT        No    Yes Yes     Interrupt(gdb) b autovacuum.c:launch_workerBreakpoint 1 at 0x82f3e7: file autovacuum.c, line 1338.(gdb) b autovacuum.c:783Breakpoint 2 at 0x82e8f0: file autovacuum.c, line 783.(gdb) cContinuing.

在其他session执行更新等操作

[pg12@localhost test]$ psql -c "update tbl set id = 1;"Expanded display is used automatically.UPDATE 2000000[pg12@localhost test]$ psql -c "update t1 set id = 1;"Expanded display is used automatically.UPDATE 20000[pg12@localhost test]$ psql -c "update t2 set id = 1;"Expanded display is used automatically.UPDATE 10000[pg12@localhost test]$ psql -c "select txid_current();"Expanded display is used automatically. txid_current --------------         2917(1 row)

60s后在gdb console中continue

Breakpoint 2, AutoVacLauncherMain (argc=0, argv=0x0) at autovacuum.c:783783         if (dlist_is_empty(&DatabaseList))(gdb) n804             avdb = dlist_tail_element(avl_dbase, adl_node, &DatabaseList);(gdb) n810             if (TimestampDifferenceExceeds(avdb->adl_next_worker,(gdb) 812                 launch_worker(current_time);(gdb) p *avdb$1 = {adl_datid = 16384, adl_next_worker = 628852948486950, adl_score = 0, adl_node = {    prev = 0xfd9880 , next = 0xfd9880 }}(gdb) stepBreakpoint 1, launch_worker (now=628853296722794) at autovacuum.c:13381338        dbid = do_start_worker();

进入do_start_worker

(gdb) stepdo_start_worker () at autovacuum.c:11281128        bool        skipit = false;(gdb) n1129        Oid         retval = InvalidOid;(gdb) 1134        LWLockAcquire(AutovacuumLock, LW_SHARED);(gdb) 1135        if (dlist_is_empty(&AutoVacuumShmem->av_freeWorkers))

查看AutoVacuumShmem结构体

(gdb) p *AutoVacuumShmem$2 = {av_signal = {0, 0}, av_launcherpid = 5476, av_freeWorkers = {head = {prev = 0x7f8ccf1a4938,       next = 0x7f8ccf1a49b8}}, av_runningWorkers = {head = {prev = 0x7f8ccf1a3520, next = 0x7f8ccf1a3520}},   av_startingWorker = 0x0, av_workItems = {{avw_type = AVW_BRINSummarizeRange, avw_used = false,       avw_active = false, avw_database = 0, avw_relation = 0, avw_blockNumber = 0} }}(gdb) n1140        LWLockRelease(AutovacuumLock);(gdb) p AutoVacuumShmem->av_runningWorkers$3 = {head = {prev = 0x7f8ccf1a3520, next = 0x7f8ccf1a3520}}(gdb) n

找到需要vacuum的database

1146        tmpcxt = AllocSetContextCreate(CurrentMemoryContext,(gdb) 1149        oldcxt = MemoryContextSwitchTo(tmpcxt);(gdb) 1152        autovac_refresh_stats();(gdb) n1155        dblist = get_database_list();(gdb) 1162        recentXid = ReadNewTransactionId();(gdb) p *dblist$8 = {type = T_List, length = 5, head = 0x2382d48, tail = 0x2382f90}(gdb) n1163        xidForceLimit = recentXid - autovacuum_freeze_max_age;(gdb) p recentXid$9 = 2917(gdb) p autovacuum_freeze_max_age$10 = 200000000(gdb) n1166        if (xidForceLimit < FirstNormalTransactionId)(gdb) p xidForceLimit$11 = 4094970213(gdb) p FirstNormalTransactionId$12 = 3(gdb) n1170        recentMulti = ReadNextMultiXactId();(gdb) 1171        multiForceLimit = recentMulti - MultiXactMemberFreezeThreshold();(gdb) 1172        if (multiForceLimit < FirstMultiXactId)(gdb) p recentMulti$13 = 1(gdb) p MultiXactMemberFreezeThreshold()$14 = 400000000(gdb) n1196        avdb = NULL;(gdb) 1197        for_xid_wrap = false;(gdb) 1198        for_multi_wrap = false;(gdb) 1199        current_time = GetCurrentTimestamp();(gdb) 1200        foreach(cell, dblist)(gdb) 1202            avw_dbase  *tmp = lfirst(cell);(gdb) 1206            if (TransactionIdPrecedes(tmp->adw_frozenxid, xidForceLimit))(gdb) p *tmp --> 这是postgres数据库$15 = {adw_datid = 13591, adw_name = 0x2382d20 "postgres", adw_frozenxid = 479, adw_minmulti = 1,   adw_entry = 0x0}(gdb) n1215            else if (for_xid_wrap)(gdb) 1217            else if (MultiXactIdPrecedes(tmp->adw_minmulti, multiForceLimit))(gdb) 1225            else if (for_multi_wrap)(gdb) 1229            tmp->adw_entry = pgstat_fetch_stat_dbentry(tmp->adw_datid);(gdb) 1235            if (!tmp->adw_entry)(gdb) 1236                continue;(gdb) 1200        foreach(cell, dblist)(gdb) 1202            avw_dbase  *tmp = lfirst(cell);(gdb) 1206            if (TransactionIdPrecedes(tmp->adw_frozenxid, xidForceLimit))(gdb) p *tmp --> 这是testdb数据库$16 = {adw_datid = 16384, adw_name = 0x2382de0 "testdb", adw_frozenxid = 531, adw_minmulti = 1, adw_entry = 0x0}(gdb) p tmp->adw_frozenxid$17 = 531(gdb) p xidForceLimit$18 = 4094970213(gdb) n1215            else if (for_xid_wrap)(gdb) 1217            else if (MultiXactIdPrecedes(tmp->adw_minmulti, multiForceLimit))(gdb) 1225            else if (for_multi_wrap)(gdb) 1229            tmp->adw_entry = pgstat_fetch_stat_dbentry(tmp->adw_datid);(gdb) 1235            if (!tmp->adw_entry)(gdb) 1245            skipit = false;(gdb) 1247            dlist_reverse_foreach(iter, &DatabaseList)(gdb) 1249                avl_dbase  *dbp = dlist_container(avl_dbase, adl_node, iter.cur);(gdb) 1251                if (dbp->adl_datid == tmp->adw_datid)(gdb) 1257                    if (!TimestampDifferenceExceeds(dbp->adl_next_worker,(gdb) 1267            if (skipit)(gdb) 1274            if (avdb == NULL ||(gdb) 1276                avdb = tmp;(gdb) n1200        foreach(cell, dblist)(gdb) 1202            avw_dbase  *tmp = lfirst(cell);(gdb) 1206            if (TransactionIdPrecedes(tmp->adw_frozenxid, xidForceLimit))(gdb) 1215            else if (for_xid_wrap)(gdb) p *tmp$19 = {adw_datid = 1, adw_name = 0x2382e60 "template1", adw_frozenxid = 479, adw_minmulti = 1, adw_entry = 0x0}(gdb) n1217            else if (MultiXactIdPrecedes(tmp->adw_minmulti, multiForceLimit))(gdb) 1225            else if (for_multi_wrap)(gdb) 1229            tmp->adw_entry = pgstat_fetch_stat_dbentry(tmp->adw_datid);(gdb) 1235            if (!tmp->adw_entry)(gdb) 1236                continue; --> 没有统计信息的,忽略(gdb) 1200        foreach(cell, dblist)(gdb) 1202            avw_dbase  *tmp = lfirst(cell);(gdb) 1206            if (TransactionIdPrecedes(tmp->adw_frozenxid, xidForceLimit))(gdb) 1215            else if (for_xid_wrap)(gdb) 1217            else if (MultiXactIdPrecedes(tmp->adw_minmulti, multiForceLimit))(gdb) 1225            else if (for_multi_wrap)(gdb) 1229            tmp->adw_entry = pgstat_fetch_stat_dbentry(tmp->adw_datid);(gdb) 1235            if (!tmp->adw_entry)(gdb) 1236                continue;(gdb) 1200        foreach(cell, dblist)(gdb) 1202            avw_dbase  *tmp = lfirst(cell);(gdb) 1206            if (TransactionIdPrecedes(tmp->adw_frozenxid, xidForceLimit))(gdb) 1215            else if (for_xid_wrap)(gdb) 1217            else if (MultiXactIdPrecedes(tmp->adw_minmulti, multiForceLimit))(gdb) 1225            else if (for_multi_wrap)(gdb) 1229            tmp->adw_entry = pgstat_fetch_stat_dbentry(tmp->adw_datid);(gdb) 1235            if (!tmp->adw_entry)(gdb) 1236                continue;(gdb) 1200        foreach(cell, dblist)(gdb)

完成db遍历,找到了需要处理的数据库->testdb,接下来就是找空闲worker并启动此worker执行vacuum

1280        if (avdb != NULL)(gdb) 1285            LWLockAcquire(AutovacuumLock, LW_EXCLUSIVE);(gdb) 1291            wptr = dlist_pop_head_node(&AutoVacuumShmem->av_freeWorkers);(gdb) 1293            worker = dlist_container(WorkerInfoData, wi_links, wptr);(gdb) p *wptr$20 = {prev = 0x7f8ccf1a3510, next = 0x7f8ccf1a4978}(gdb) n1294            worker->wi_dboid = avdb->adw_datid;(gdb) p *worker$21 = {wi_links = {prev = 0x7f8ccf1a3510, next = 0x7f8ccf1a4978}, wi_dboid = 0, wi_tableoid = 0, wi_proc = 0x0,   wi_launchtime = 0, wi_dobalance = false, wi_sharedrel = false, wi_cost_delay = 0, wi_cost_limit = 0,   wi_cost_limit_base = 0}(gdb) n1295            worker->wi_proc = NULL;(gdb) 1296            worker->wi_launchtime = GetCurrentTimestamp();(gdb) 1298            AutoVacuumShmem->av_startingWorker = worker;(gdb) 1300            LWLockRelease(AutovacuumLock);(gdb) 1302            SendPostmasterSignal(PMSIGNAL_START_AUTOVAC_WORKER);(gdb) p *AutoVacuumShmem$22 = {av_signal = {0, 0}, av_launcherpid = 5476, av_freeWorkers = {head = {prev = 0x7f8ccf1a4938,       next = 0x7f8ccf1a4978}}, av_runningWorkers = {head = {prev = 0x7f8ccf1a3520, next = 0x7f8ccf1a3520}},   av_startingWorker = 0x7f8ccf1a49b8, av_workItems = {{avw_type = AVW_BRINSummarizeRange, avw_used = false,       avw_active = false, avw_database = 0, avw_relation = 0, avw_blockNumber = 0} }}(gdb) n1304            retval = avdb->adw_datid;(gdb) Program received signal SIGUSR2, User defined signal 2.do_start_worker () at autovacuum.c:13041304            retval = avdb->adw_datid;(gdb) avl_sigusr2_handler (postgres_signal_arg=32764) at autovacuum.c:14051405    {(gdb)

DONE!

四、参考资料

PG Source Code