本文简单介绍了PG插入数据部分的源码，主要内容包括PortalRunMulti函数和PortalRun函数的实现逻辑，PortalRunMulti函数和PortalRun均位于pquery.c文件中。

一、基础信息

PortalRunMulti函数使用的数据结构、宏定义以及依赖的函数等。

typedef struct PortalData *Portal;  typedef struct PortalData {     /* Bookkeeping data */     const char *name;           /* portal's name */     const char *prepStmtName;   /* source prepared statement (NULL if none) */     MemoryContext portalContext;    /* subsidiary memory for portal */     ResourceOwner resowner;     /* resources owned by portal */     void        (*cleanup) (Portal portal); /* cleanup hook */      /*      * State data for remembering which subtransaction(s) the portal was      * created or used in.  If the portal is held over from a previous      * transaction, both subxids are InvalidSubTransactionId.  Otherwise,      * createSubid is the creating subxact and activeSubid is the last subxact      * in which we ran the portal.      */     SubTransactionId createSubid;   /* the creating subxact */     SubTransactionId activeSubid;   /* the last subxact with activity */      /* The query or queries the portal will execute */     const char *sourceText;     /* text of query (as of 8.4, never NULL) */     const char *commandTag;     /* command tag for original query */     List       *stmts;          /* list of PlannedStmts */     CachedPlan *cplan;          /* CachedPlan, if stmts are from one */      ParamListInfo portalParams; /* params to pass to query */     QueryEnvironment *queryEnv; /* environment for query */      /* Features/options */     PortalStrategy strategy;    /* see above */     int         cursorOptions;  /* DECLARE CURSOR option bits */     bool        run_once;       /* portal will only be run once */      /* Status data */     PortalStatus status;        /* see above */     bool        portalPinned;   /* a pinned portal can't be dropped */     bool        autoHeld;       /* was automatically converted from pinned to                                  * held (see HoldPinnedPortals()) */      /* If not NULL, Executor is active; call ExecutorEnd eventually: */     QueryDesc  *queryDesc;      /* info needed for executor invocation */      /* If portal returns tuples, this is their tupdesc: */     TupleDesc   tupDesc;        /* descriptor for result tuples */     /* and these are the format codes to use for the columns: */     int16      *formats;        /* a format code for each column */      /*      * Where we store tuples for a held cursor or a PORTAL_ONE_RETURNING or      * PORTAL_UTIL_SELECT query.  (A cursor held past the end of its      * transaction no longer has any active executor state.)      */     Tuplestorestate *holdStore; /* store for holdable cursors */     MemoryContext holdContext;  /* memory containing holdStore */      /*      * Snapshot under which tuples in the holdStore were read.  We must keep a      * reference to this snapshot if there is any possibility that the tuples      * contain TOAST references, because releasing the snapshot could allow      * recently-dead rows to be vacuumed away, along with any toast data      * belonging to them.  In the case of a held cursor, we avoid needing to      * keep such a snapshot by forcibly detoasting the data.      */     Snapshot    holdSnapshot;   /* registered snapshot, or NULL if none */      /*      * atStart, atEnd and portalPos indicate the current cursor position.      * portalPos is zero before the first row, N after fetching N'th row of      * query.  After we run off the end, portalPos = # of rows in query, and      * atEnd is true.  Note that atStart implies portalPos == 0, but not the      * reverse: we might have backed up only as far as the first row, not to      * the start.  Also note that various code inspects atStart and atEnd, but      * only the portal movement routines should touch portalPos.      */     bool        atStart;     bool        atEnd;     uint64      portalPos;      /* Presentation data, primarily used by the pg_cursors system view */     TimestampTz creation_time;  /* time at which this portal was defined */     bool        visible;        /* include this portal in pg_cursors? */ }           PortalData;

2、List

typedef struct ListCell ListCell;  typedef struct List {     NodeTag     type;           /* T_List, T_IntList, or T_OidList */     int         length;     ListCell   *head;     ListCell   *tail; } List;  struct ListCell {     union     {         void       *ptr_value;         int         int_value;         Oid         oid_value;     }           data;     ListCell   *next; };

3、Snapshot

typedef struct SnapshotData *Snapshot; /*  * Struct representing all kind of possible snapshots.  *  * There are several different kinds of snapshots:  * * Normal MVCC snapshots  * * MVCC snapshots taken during recovery (in Hot-Standby mode)  * * Historic MVCC snapshots used during logical decoding  * * snapshots passed to HeapTupleSatisfiesDirty()  * * snapshots passed to HeapTupleSatisfiesNonVacuumable()  * * snapshots used for SatisfiesAny, Toast, Self where no members are  *   accessed.  *  * TODO: It's probably a good idea to split this struct using a NodeTag  * similar to how parser and executor nodes are handled, with one type for  * each different kind of snapshot to avoid overloading the meaning of  * individual fields.  */ typedef struct SnapshotData {     SnapshotSatisfiesFunc satisfies;    /* tuple test function */      /*      * The remaining fields are used only for MVCC snapshots, and are normally      * just zeroes in special snapshots.  (But xmin and xmax are used      * specially by HeapTupleSatisfiesDirty, and xmin is used specially by      * HeapTupleSatisfiesNonVacuumable.)      *      * An MVCC snapshot can never see the effects of XIDs >= xmax. It can see      * the effects of all older XIDs except those listed in the snapshot. xmin      * is stored as an optimization to avoid needing to search the XID arrays      * for most tuples.      */     TransactionId xmin;         /* all XID < xmin are visible to me */     TransactionId xmax;         /* all XID >= xmax are invisible to me */      /*      * For normal MVCC snapshot this contains the all xact IDs that are in      * progress, unless the snapshot was taken during recovery in which case      * it's empty. For historic MVCC snapshots, the meaning is inverted, i.e.      * it contains *committed* transactions between xmin and xmax.      *      * note: all ids in xip[] satisfy xmin <= xip[i] < xmax      */     TransactionId *xip;     uint32      xcnt;           /* # of xact ids in xip[] */      /*      * For non-historic MVCC snapshots, this contains subxact IDs that are in      * progress (and other transactions that are in progress if taken during      * recovery). For historic snapshot it contains *all* xids assigned to the      * replayed transaction, including the toplevel xid.      *      * note: all ids in subxip[] are >= xmin, but we don't bother filtering      * out any that are >= xmax      */     TransactionId *subxip;     int32       subxcnt;        /* # of xact ids in subxip[] */     bool        suboverflowed;  /* has the subxip array overflowed? */      bool        takenDuringRecovery;    /* recovery-shaped snapshot? */     bool        copied;         /* false if it's a static snapshot */      CommandId   curcid;         /* in my xact, CID < curcid are visible */      /*      * An extra return value for HeapTupleSatisfiesDirty, not used in MVCC      * snapshots.      */     uint32      speculativeToken;      /*      * Book-keeping information, used by the snapshot manager      */     uint32      active_count;   /* refcount on ActiveSnapshot stack */     uint32      regd_count;     /* refcount on RegisteredSnapshots */     pairingheap_node ph_node;   /* link in the RegisteredSnapshots heap */      TimestampTz whenTaken;      /* timestamp when snapshot was taken */     XLogRecPtr  lsn;            /* position in the WAL stream when taken */ } SnapshotData;

依赖的函数

/*  * NB: There is an unfortunate legacy from a previous incarnation of  * the List API: the macro lfirst() was used to mean "the data in this  * cons cell". To avoid changing every usage of lfirst(), that meaning  * has been kept. As a result, lfirst() takes a ListCell and returns  * the data it contains; to get the data in the first cell of a  * List, use linitial(). Worse, lsecond() is more closely related to  * linitial() than lfirst(): given a List, lsecond() returns the data  * in the second cons cell.  */ #define lnext(lc)               ((lc)->next) #define lfirst(lc)              ((lc)->data.ptr_value) #define lfirst_int(lc)          ((lc)->data.int_value) #define lfirst_oid(lc)          ((lc)->data.oid_value) #define lfirst_node(type,lc)    castNode(type, lfirst(lc)) /*  * castNode(type, ptr) casts ptr to "type *", and if assertions are enabled,  * verifies that the node has the appropriate type (using its nodeTag()).  *  * Use an inline function when assertions are enabled, to avoid multiple  * evaluations of the ptr argument (which could e.g. be a function call).  */ #ifdef USE_ASSERT_CHECKING static inline Node * castNodeImpl(NodeTag type, void *ptr) {     Assert(ptr == NULL || nodeTag(ptr) == type);     return (Node *) ptr; } #define castNode(_type_, nodeptr) ((_type_ *) castNodeImpl(T_##_type_, nodeptr)) #else #define castNode(_type_, nodeptr) ((_type_ *) (nodeptr)) #endif                          /* USE_ASSERT_CHECKING */

2、Snapshot相关

//留待MVCC再行解读GetTransactionSnapshotRegisterSnapshotPushCopiedSnapshotUpdateActiveSnapshotCommandIdPopActiveSnapshot

3、ProcessQuery

//上一节已介绍

4、CommandCounterIncrement

/*  *  CommandCounterIncrement  */ void CommandCounterIncrement(void) {     /*      * If the current value of the command counter hasn't been "used" to mark      * tuples, we need not increment it, since there's no need to distinguish      * a read-only command from others.  This helps postpone command counter      * overflow, and keeps no-op CommandCounterIncrement operations cheap.      */     if (currentCommandIdUsed)     {         /*          * Workers synchronize transaction state at the beginning of each          * parallel operation, so we can't account for new commands after that          * point.          */         if (IsInParallelMode() || IsParallelWorker())             elog(ERROR, "cannot start commands during a parallel operation");          currentCommandId += 1;         if (currentCommandId == InvalidCommandId)         {             currentCommandId -= 1;             ereport(ERROR,                     (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),                      errmsg("cannot have more than 2^32-2 commands in a transaction")));         }         currentCommandIdUsed = false;          /* Propagate new command ID into static snapshots */         SnapshotSetCommandId(currentCommandId);          /*          * Make any catalog changes done by the just-completed command visible          * in the local syscache.  We obviously don't need to do this after a          * read-only command.  (But see hacks in inval.c to make real sure we          * don't think a command that queued inval messages was read-only.)          */         AtCCI_LocalCache();     } }

5、MemoryContextDeleteChildren

/*  * MemoryContextDeleteChildren  *      Delete all the descendants of the named context and release all  *      space allocated therein.  The named context itself is not touched.  */ void MemoryContextDeleteChildren(MemoryContext context) {     AssertArg(MemoryContextIsValid(context));      /*      * MemoryContextDelete will delink the child from me, so just iterate as      * long as there is a child.      */     while (context->firstchild != NULL)         MemoryContextDelete(context->firstchild); }

二、源码解读

1、PortalRun

/* * PortalRun *      Run a portal's query or queries. * * count <= 0 is interpreted as a no-op: the destination gets started up * and shut down, but nothing else happens.  Also, count == FETCH_ALL is * interpreted as "all rows".  Note that count is ignored in multi-query * situations, where we always run the portal to completion. * * isTopLevel: true if query is being executed at backend "top level" * (that is, directly from a client command message) * * dest: where to send output of primary (canSetTag) query * * altdest: where to send output of non-primary queries * * completionTag: points to a buffer of size COMPLETION_TAG_BUFSIZE *      in which to store a command completion status string. *      May be NULL if caller doesn't want a status string. * * Returns true if the portal's execution is complete, false if it was * suspended due to exhaustion of the count parameter. *//*输入：    参照PortalRunMulti输出：    布尔变量，成功true，失败false*/boolPortalRun(Portal portal, long count, bool isTopLevel, bool run_once,          DestReceiver *dest, DestReceiver *altdest,          char *completionTag){    bool        result;//返回结果    uint64      nprocessed;    ResourceOwner saveTopTransactionResourceOwner;//高层事务资源宿主    MemoryContext saveTopTransactionContext;//内存上下文    Portal      saveActivePortal;//活动的Portal    ResourceOwner saveResourceOwner;    MemoryContext savePortalContext;    MemoryContext saveMemoryContext;    AssertArg(PortalIsValid(portal));    TRACE_POSTGRESQL_QUERY_EXECUTE_START();    /* Initialize completion tag to empty string */    if (completionTag)        completionTag[0] = '\0';    if (log_executor_stats && portal->strategy != PORTAL_MULTI_QUERY)    {        elog(DEBUG3, "PortalRun");        /* PORTAL_MULTI_QUERY logs its own stats per query */        ResetUsage();    }    /*     * Check for improper portal use, and mark portal active.     */    MarkPortalActive(portal);    /* Set run_once flag.  Shouldn't be clear if previously set. */    Assert(!portal->run_once || run_once);    portal->run_once = run_once;    /*     * Set up global portal context pointers.     *     * We have to play a special game here to support utility commands like     * VACUUM and CLUSTER, which internally start and commit transactions.     * When we are called to execute such a command, CurrentResourceOwner will     * be pointing to the TopTransactionResourceOwner --- which will be     * destroyed and replaced in the course of the internal commit and     * restart.  So we need to be prepared to restore it as pointing to the     * exit-time TopTransactionResourceOwner.  (Ain't that ugly?  This idea of     * internally starting whole new transactions is not good.)     * CurrentMemoryContext has a similar problem, but the other pointers we     * save here will be NULL or pointing to longer-lived objects.     */    //保护现场    saveTopTransactionResourceOwner = TopTransactionResourceOwner;    saveTopTransactionContext = TopTransactionContext;    saveActivePortal = ActivePortal;    saveResourceOwner = CurrentResourceOwner;    savePortalContext = PortalContext;    saveMemoryContext = CurrentMemoryContext;    PG_TRY();    {        ActivePortal = portal;        if (portal->resowner)            CurrentResourceOwner = portal->resowner;        PortalContext = portal->portalContext;        MemoryContextSwitchTo(PortalContext);        switch (portal->strategy)        {            case PORTAL_ONE_SELECT:            case PORTAL_ONE_RETURNING:            case PORTAL_ONE_MOD_WITH:            case PORTAL_UTIL_SELECT:                /*                 * If we have not yet run the command, do so, storing its                 * results in the portal's tuplestore.  But we don't do that                 * for the PORTAL_ONE_SELECT case.                 */                if (portal->strategy != PORTAL_ONE_SELECT && !portal->holdStore)                    FillPortalStore(portal, isTopLevel);                /*                 * Now fetch desired portion of results.                 */                nprocessed = PortalRunSelect(portal, true, count, dest);                /*                 * If the portal result contains a command tag and the caller                 * gave us a pointer to store it, copy it. Patch the "SELECT"                 * tag to also provide the rowcount.                 */                if (completionTag && portal->commandTag)                {                    if (strcmp(portal->commandTag, "SELECT") == 0)                        snprintf(completionTag, COMPLETION_TAG_BUFSIZE,                                 "SELECT " UINT64_FORMAT, nprocessed);                    else                        strcpy(completionTag, portal->commandTag);                }                /* Mark portal not active */                portal->status = PORTAL_READY;                /*                 * Since it's a forward fetch, say DONE iff atEnd is now true.                 */                result = portal->atEnd;                break;            case PORTAL_MULTI_QUERY://INSERT语句                PortalRunMulti(portal, isTopLevel, false,                               dest, altdest, completionTag);                /* Prevent portal's commands from being re-executed */                MarkPortalDone(portal);                /* Always complete at end of RunMulti */                result = true;                break;            default:                elog(ERROR, "unrecognized portal strategy: %d",                     (int) portal->strategy);                result = false; /* keep compiler quiet */                break;        }    }    PG_CATCH();    {        /* Uncaught error while executing portal: mark it dead */        MarkPortalFailed(portal);        /* Restore global vars and propagate error */        if (saveMemoryContext == saveTopTransactionContext)            MemoryContextSwitchTo(TopTransactionContext);        else            MemoryContextSwitchTo(saveMemoryContext);        ActivePortal = saveActivePortal;        if (saveResourceOwner == saveTopTransactionResourceOwner)            CurrentResourceOwner = TopTransactionResourceOwner;        else            CurrentResourceOwner = saveResourceOwner;        PortalContext = savePortalContext;        PG_RE_THROW();    }    PG_END_TRY();    if (saveMemoryContext == saveTopTransactionContext)        MemoryContextSwitchTo(TopTransactionContext);    else        MemoryContextSwitchTo(saveMemoryContext);    ActivePortal = saveActivePortal;    if (saveResourceOwner == saveTopTransactionResourceOwner)        CurrentResourceOwner = TopTransactionResourceOwner;    else        CurrentResourceOwner = saveResourceOwner;    PortalContext = savePortalContext;    if (log_executor_stats && portal->strategy != PORTAL_MULTI_QUERY)        ShowUsage("EXECUTOR STATISTICS");    TRACE_POSTGRESQL_QUERY_EXECUTE_DONE();    return result;}

2、PortalRunMulti

/* * PortalRunMulti *      Execute a portal's queries in the general case (multi queries *      or non-SELECT-like queries) *//*输入：    portal-“门户”数据结构    isTopLevel-顶层？    setHoldSnapshot-是否持有快照    dest-目标端    altdest-?    completionTag-完成标记（用于语句执行结果输出）输出：    无*/static voidPortalRunMulti(Portal portal,               bool isTopLevel, bool setHoldSnapshot,               DestReceiver *dest, DestReceiver *altdest,               char *completionTag){    bool        active_snapshot_set = false;//活跃snapshot？    ListCell   *stmtlist_item;//SQL语句，临时变量    /*     * If the destination is DestRemoteExecute, change to DestNone.  The     * reason is that the client won't be expecting any tuples, and indeed has     * no way to know what they are, since there is no provision for Describe     * to send a RowDescription message when this portal execution strategy is     * in effect.  This presently will only affect SELECT commands added to     * non-SELECT queries by rewrite rules: such commands will be executed,     * but the results will be discarded unless you use "simple Query"     * protocol.     */    if (dest->mydest == DestRemoteExecute)        dest = None_Receiver;    if (altdest->mydest == DestRemoteExecute)        altdest = None_Receiver;    /*     * Loop to handle the individual queries generated from a single parsetree     * by analysis and rewrite.     */    foreach(stmtlist_item, portal->stmts)//循环处理SQL语句    {        PlannedStmt *pstmt = lfirst_node(PlannedStmt, stmtlist_item);//获取已规划的语句        /*         * If we got a cancel signal in prior command, quit         */        CHECK_FOR_INTERRUPTS();        if (pstmt->utilityStmt == NULL)//非“工具类”语句        {            /*             * process a plannable query.             */            TRACE_POSTGRESQL_QUERY_EXECUTE_START();            if (log_executor_stats)                ResetUsage();            /*             * Must always have a snapshot for plannable queries.  First time             * through, take a new snapshot; for subsequent queries in the             * same portal, just update the snapshot's copy of the command             * counter.             */            if (!active_snapshot_set)            {                Snapshot    snapshot = GetTransactionSnapshot();//获取事务快照                /* If told to, register the snapshot and save in portal */                if (setHoldSnapshot)                {                    snapshot = RegisterSnapshot(snapshot);                    portal->holdSnapshot = snapshot;                }                /*                 * We can't have the holdSnapshot also be the active one,                 * because UpdateActiveSnapshotCommandId would complain.  So                 * force an extra snapshot copy.  Plain PushActiveSnapshot                 * would have copied the transaction snapshot anyway, so this                 * only adds a copy step when setHoldSnapshot is true.  (It's                 * okay for the command ID of the active snapshot to diverge                 * from what holdSnapshot has.)                 */                PushCopiedSnapshot(snapshot);                active_snapshot_set = true;            }            else                UpdateActiveSnapshotCommandId();            //处理查询            if (pstmt->canSetTag)            {                /* statement can set tag string */                ProcessQuery(pstmt,                             portal->sourceText,                             portal->portalParams,                             portal->queryEnv,                             dest, completionTag);            }            else            {                /* stmt added by rewrite cannot set tag */                ProcessQuery(pstmt,                             portal->sourceText,                             portal->portalParams,                             portal->queryEnv,                             altdest, NULL);            }            if (log_executor_stats)                ShowUsage("EXECUTOR STATISTICS");            TRACE_POSTGRESQL_QUERY_EXECUTE_DONE();        }        else//“工具类”语句        {            /*             * process utility functions (create, destroy, etc..)             *             * We must not set a snapshot here for utility commands (if one is             * needed, PortalRunUtility will do it).  If a utility command is             * alone in a portal then everything's fine.  The only case where             * a utility command can be part of a longer list is that rules             * are allowed to include NotifyStmt.  NotifyStmt doesn't care             * whether it has a snapshot or not, so we just leave the current             * snapshot alone if we have one.             */            if (pstmt->canSetTag)            {                Assert(!active_snapshot_set);                /* statement can set tag string */                PortalRunUtility(portal, pstmt, isTopLevel, false,                                 dest, completionTag);            }            else            {                Assert(IsA(pstmt->utilityStmt, NotifyStmt));                /* stmt added by rewrite cannot set tag */                PortalRunUtility(portal, pstmt, isTopLevel, false,                                 altdest, NULL);            }        }        /*         * Increment command counter between queries, but not after the last         * one.         */        if (lnext(stmtlist_item) != NULL)            CommandCounterIncrement();        /*         * Clear subsidiary contexts to recover temporary memory.         */        Assert(portal->portalContext == CurrentMemoryContext);        MemoryContextDeleteChildren(portal->portalContext);//释放资源    }    /* Pop the snapshot if we pushed one. */    if (active_snapshot_set)        PopActiveSnapshot();    /*     * If a command completion tag was supplied, use it.  Otherwise use the     * portal's commandTag as the default completion tag.     *     * Exception: Clients expect INSERT/UPDATE/DELETE tags to have counts, so     * fake them with zeros.  This can happen with DO INSTEAD rules if there     * is no replacement query of the same type as the original.  We print "0     * 0" here because technically there is no query of the matching tag type,     * and printing a non-zero count for a different query type seems wrong,     * e.g.  an INSERT that does an UPDATE instead should not print "0 1" if     * one row was updated.  See QueryRewrite(), step 3, for details.     */    if (completionTag && completionTag[0] == '\0')//操作提示    {        if (portal->commandTag)            strcpy(completionTag, portal->commandTag);        if (strcmp(completionTag, "SELECT") == 0)            sprintf(completionTag, "SELECT 0 0");        else if (strcmp(completionTag, "INSERT") == 0)            strcpy(completionTag, "INSERT 0 0");        else if (strcmp(completionTag, "UPDATE") == 0)            strcpy(completionTag, "UPDATE 0");        else if (strcmp(completionTag, "DELETE") == 0)            strcpy(completionTag, "DELETE 0");    }}

三、跟踪分析

插入测试数据：

testdb=# -- 获取pidtestdb=# select pg_backend_pid(); pg_backend_pid ----------------           2551(1 row)testdb=# -- 插入1行testdb=# insert into t_insert values(20,'PortalRun','PortalRun','PortalRun');

启动gdb，跟踪调试：

[root@localhost ~]# gdb -p 2551GNU gdb (GDB) Red Hat Enterprise Linux 7.6.1-100.el7Copyright (C) 2013 Free Software Foundation, Inc....(gdb) b PortalRunBreakpoint 1 at 0x8528af: file pquery.c, line 707.(gdb) cContinuing.Breakpoint 1, PortalRun (portal=0x2c6f490, count=9223372036854775807, isTopLevel=true, run_once=true, dest=0x2ccb4d8, altdest=0x2ccb4d8, completionTag=0x7ffe94ba4940 "") at pquery.c:707707     if (completionTag)#查看输入参数#1、portal(gdb) p *portal$1 = {name = 0x2c72e98 "", prepStmtName = 0x0, portalContext = 0x2cc1470, resowner = 0x2c3ad10, cleanup = 0x62f15c 
     
      , createSubid = 1, activeSubid = 1,   sourceText = 0x2c09ef0 "insert into t_insert values(20,'PortalRun','PortalRun','PortalRun');", commandTag = 0xb50908 "INSERT", stmts = 0x2ccb4a8, cplan = 0x0, portalParams = 0x0, queryEnv = 0x0,   strategy = PORTAL_MULTI_QUERY, cursorOptions = 4, run_once = false, status = PORTAL_READY, portalPinned = false, autoHeld = false, queryDesc = 0x0, tupDesc = 0x0, formats = 0x0, holdStore = 0x0,   holdContext = 0x0, holdSnapshot = 0x0, atStart = true, atEnd = true, portalPos = 0, creation_time = 587033564125509, visible = false}(gdb) p *(portal->portalContext)$2 = {type = T_AllocSetContext, isReset = true, allowInCritSection = false, methods = 0xb8c720 
      
       , parent = 0x2c6f380, firstchild = 0x0, prevchild = 0x0, nextchild = 0x0,   name = 0xb8d2f1 "PortalContext", ident = 0x2c72e98 "", reset_cbs = 0x0}(gdb) p *(portal->resowner)$3 = {parent = 0x2c35518, firstchild = 0x0, nextchild = 0x0, name = 0xb8d2ff "Portal", bufferarr = {itemsarr = 0x0, invalidval = 0, capacity = 0, nitems = 0, maxitems = 0, lastidx = 0}, catrefarr = {    itemsarr = 0x0, invalidval = 0, capacity = 0, nitems = 0, maxitems = 0, lastidx = 0}, catlistrefarr = {itemsarr = 0x0, invalidval = 0, capacity = 0, nitems = 0, maxitems = 0, lastidx = 0},   relrefarr = {itemsarr = 0x0, invalidval = 0, capacity = 0, nitems = 0, maxitems = 0, lastidx = 0}, planrefarr = {itemsarr = 0x0, invalidval = 0, capacity = 0, nitems = 0, maxitems = 0, lastidx = 0},   tupdescarr = {itemsarr = 0x0, invalidval = 0, capacity = 0, nitems = 0, maxitems = 0, lastidx = 0}, snapshotarr = {itemsarr = 0x0, invalidval = 0, capacity = 0, nitems = 0, maxitems = 0,     lastidx = 0}, filearr = {itemsarr = 0x0, invalidval = 18446744073709551615, capacity = 0, nitems = 0, maxitems = 0, lastidx = 0}, dsmarr = {itemsarr = 0x0, invalidval = 0, capacity = 0,     nitems = 0, maxitems = 0, lastidx = 0}, jitarr = {itemsarr = 0x0, invalidval = 0, capacity = 0, nitems = 0, maxitems = 0, lastidx = 0}, nlocks = 0, locks = {0x0 
       
        }}(gdb) p *(portal->resowner->parent)$4 = {parent = 0x0, firstchild = 0x2c3ad10, nextchild = 0x0, name = 0xa1b515 "TopTransaction", bufferarr = {itemsarr = 0x0, invalidval = 0, capacity = 0, nitems = 0, maxitems = 0, lastidx = 0},   catrefarr = {itemsarr = 0x2c3b040, invalidval = 0, capacity = 16, nitems = 0, maxitems = 16, lastidx = 4294967295}, catlistrefarr = {itemsarr = 0x0, invalidval = 0, capacity = 0, nitems = 0,     maxitems = 0, lastidx = 0}, relrefarr = {itemsarr = 0x2c35728, invalidval = 0, capacity = 16, nitems = 0, maxitems = 16, lastidx = 4294967295}, planrefarr = {itemsarr = 0x0, invalidval = 0,     capacity = 0, nitems = 0, maxitems = 0, lastidx = 0}, tupdescarr = {itemsarr = 0x0, invalidval = 0, capacity = 0, nitems = 0, maxitems = 0, lastidx = 0}, snapshotarr = {itemsarr = 0x0,     invalidval = 0, capacity = 0, nitems = 0, maxitems = 0, lastidx = 0}, filearr = {itemsarr = 0x0, invalidval = 18446744073709551615, capacity = 0, nitems = 0, maxitems = 0, lastidx = 0}, dsmarr = {    itemsarr = 0x0, invalidval = 0, capacity = 0, nitems = 0, maxitems = 0, lastidx = 0}, jitarr = {itemsarr = 0x0, invalidval = 0, capacity = 0, nitems = 0, maxitems = 0, lastidx = 0}, nlocks = 1,   locks = {0x2c28320, 0x0 
        
         }}#2、count(gdb) p count$5 = 9223372036854775807#3、isTopLevel(gdb) p isTopLevel$6 = true#4、run_once(gdb) p run_once$7 = true#5、dest$8 = (DestReceiver *) 0x2ccb4d8(gdb) p *dest$9 = {receiveSlot = 0x4857ad 
         
          , rStartup = 0x485196 
          
           , rShutdown = 0x485bad 
           
            , rDestroy = 0x485c21 
            
             , mydest = DestRemote}(gdb) #6、altdest(gdb) p altdest$10 = (DestReceiver *) 0x2ccb4d8(gdb) p *altdest$11 = {receiveSlot = 0x4857ad 
             
              , rStartup = 0x485196 
              
               , rShutdown = 0x485bad 
               
                , rDestroy = 0x485c21 
                
                 , mydest = DestRemote}(gdb) #7、completionTag(gdb) p completionTag$12 = 0x7ffe94ba4940 ""#单步调试710 if (log_executor_stats && portal->strategy != PORTAL_MULTI_QUERY)(gdb) 720 MarkPortalActive(portal);(gdb) 724 portal->run_once = run_once;(gdb) 740 saveTopTransactionResourceOwner = TopTransactionResourceOwner;(gdb) 741 saveTopTransactionContext = TopTransactionContext;(gdb) 742 saveActivePortal = ActivePortal;(gdb) 743 saveResourceOwner = CurrentResourceOwner;(gdb) 744 savePortalContext = PortalContext;(gdb) 745 saveMemoryContext = CurrentMemoryContext;(gdb) 746 PG_TRY();(gdb) 748 ActivePortal = portal;(gdb) 749 if (portal->resowner)(gdb) 750 CurrentResourceOwner = portal->resowner;(gdb) 751 PortalContext = portal->portalContext;(gdb) 753 MemoryContextSwitchTo(PortalContext);(gdb) 755 switch (portal->strategy)(gdb) p portal->strategy$13 = PORTAL_MULTI_QUERY(gdb) next799 PortalRunMulti(portal, isTopLevel, false,(gdb) 803 MarkPortalDone(portal);(gdb) 806 result = true;(gdb) 807 break;(gdb) 835 PG_END_TRY();(gdb) 837 if (saveMemoryContext == saveTopTransactionContext)(gdb) 838 MemoryContextSwitchTo(TopTransactionContext);(gdb) 841 ActivePortal = saveActivePortal;(gdb) 842 if (saveResourceOwner == saveTopTransactionResourceOwner)(gdb) 843 CurrentResourceOwner = TopTransactionResourceOwner;(gdb) 846 PortalContext = savePortalContext;(gdb) 848 if (log_executor_stats && portal->strategy != PORTAL_MULTI_QUERY)(gdb) 853 return result;(gdb) 854 }#DONE!
                
               
              
             
            
           
          
         
        
       
      
     

2、PortalRunMulti

(gdb) b PortalRunMultiBreakpoint 1 at 0x8533df: file pquery.c, line 1210.(gdb) cContinuing.Breakpoint 1, PortalRunMulti (portal=0x2c6f490, isTopLevel=true, setHoldSnapshot=false, dest=0x2cbe8f8, altdest=0x2cbe8f8, completionTag=0x7ffe94ba4940 "") at pquery.c:12101210        bool        active_snapshot_set = false;#输入参数#1、portal(gdb) p *portal$1 = {name = 0x2c72e98 "", prepStmtName = 0x0, portalContext = 0x2c2d3d0, resowner = 0x2c3ad10, cleanup = 0x62f15c 
     
      , createSubid = 1, activeSubid = 1,   sourceText = 0x2c09ef0 "insert into t_insert values(21,'PortalRunMulti','PortalRunMulti','PortalRunMulti');", commandTag = 0xb50908 "INSERT", stmts = 0x2cbe8c8, cplan = 0x0, portalParams = 0x0,   queryEnv = 0x0, strategy = PORTAL_MULTI_QUERY, cursorOptions = 4, run_once = true, status = PORTAL_ACTIVE, portalPinned = false, autoHeld = false, queryDesc = 0x0, tupDesc = 0x0, formats = 0x0,   holdStore = 0x0, holdContext = 0x0, holdSnapshot = 0x0, atStart = true, atEnd = true, portalPos = 0, creation_time = 587034112962796, visible = false}(gdb) p *(portal->portalContext)$2 = {type = T_AllocSetContext, isReset = true, allowInCritSection = false, methods = 0xb8c720 
      
       , parent = 0x2c6f380, firstchild = 0x0, prevchild = 0x0, nextchild = 0x0,   name = 0xb8d2f1 "PortalContext", ident = 0x2c72e98 "", reset_cbs = 0x0}#2、isTopLevel(gdb) p isTopLevel$3 = true#3、setHoldSnapshot(gdb) p setHoldSnapshot$4 = false#4、dest(gdb) p *dest$5 = {receiveSlot = 0x4857ad 
       
        , rStartup = 0x485196 
        
         , rShutdown = 0x485bad 
         
          , rDestroy = 0x485c21 
          
           , mydest = DestRemote}#5、altdest(gdb) p *altdest$6 = {receiveSlot = 0x4857ad 
           
            , rStartup = 0x485196 
            
             , rShutdown = 0x485bad 
             
              , rDestroy = 0x485c21 
              
               , mydest = DestRemote}#6、completionTag(gdb) p *completionTag$7 = 0 '\000'#单步调试...(gdb) next1234 PlannedStmt *pstmt = lfirst_node(PlannedStmt, stmtlist_item);(gdb) 1239 CHECK_FOR_INTERRUPTS();(gdb) p *pstmt$12 = {type = T_PlannedStmt, commandType = CMD_INSERT, queryId = 0, hasReturning = false, hasModifyingCTE = false, canSetTag = true, transientPlan = false, dependsOnRole = false, parallelModeNeeded = false, jitFlags = 0, planTree = 0x2c0aff8, rtable = 0x2cbe7d8, resultRelations = 0x2cbe878, nonleafResultRelations = 0x0, rootResultRelations = 0x0, subplans = 0x0, rewindPlanIDs = 0x0, rowMarks = 0x0, relationOids = 0x2cbe828, invalItems = 0x0, paramExecTypes = 0x2c31700, utilityStmt = 0x0, stmt_location = 0, stmt_len = 82}(gdb) next1241 if (pstmt->utilityStmt == NULL)(gdb) 1248 if (log_executor_stats)(gdb) 1257 if (!active_snapshot_set)(gdb) 1259 Snapshot snapshot = GetTransactionSnapshot();(gdb) 1262 if (setHoldSnapshot)(gdb) p *snapshot$13 = {satisfies = 0x9f73fc 
               
                , xmin = 1612887, xmax = 1612887, xip = 0x2c2d1c0, xcnt = 0, subxip = 0x2c81c70, subxcnt = 0, suboverflowed = false, takenDuringRecovery = false, copied = false, curcid = 0, speculativeToken = 0, active_count = 0, regd_count = 0, ph_node = {first_child = 0x0, next_sibling = 0x0, prev_or_parent = 0x0}, whenTaken = 0, lsn = 0}(gdb) ...(gdb) PortalRun (portal=0x2c6f490, count=9223372036854775807, isTopLevel=true, run_once=true, dest=0x2cbe8f8, altdest=0x2cbe8f8, completionTag=0x7ffe94ba4940 "INSERT 0 1") at pquery.c:803803 MarkPortalDone(portal);#DONE!
               
              
             
            
           
          
         
        
       
      
     

四、小结

1、Portal：门户，类似设计模式中的Facade，对外的统一接口。该数据结构如何构造，有待接下来的上层函数解读。