PostgreSQL 原始碼解讀（8）- 插入資料#7（ExecutePlan）
本文簡單介紹了PG插入資料部分的原始碼，主要內容包括ExecutePlan函式的實現邏輯，該函式位於execMain.c中。
一、基礎資訊
ExecutePlan函式使用的資料結構、宏定義以及依賴的函式等。
資料結構/宏定義
1、ScanDirection
//列舉變數，掃描的方向，向後/不需要移動/向前三種
/*
* ScanDirection was an int8 for no apparent reason. I kept the original
* values because I'm not sure if I'll break anything otherwise. -ay 2/95
*/
typedef enum ScanDirection
{
BackwardScanDirection = -1,
NoMovementScanDirection = 0,
ForwardScanDirection = 1
} ScanDirection;
2、DestReceiver
//目標端接收器
//包括啟動/關閉/銷燬/接收資料的函式以及接收器的命令目標型別
/* ----------------
* DestReceiver is a base type for destination-specific local state.
* In the simplest cases, there is no state info, just the function
* pointers that the executor must call.
*
* Note: the receiveSlot routine must be passed a slot containing a TupleDesc
* identical to the one given to the rStartup routine. It returns bool where
* a "true" value means "continue processing" and a "false" value means
* "stop early, just as if we'd reached the end of the scan".
* ----------------
*/
typedef struct _DestReceiver DestReceiver;
struct _DestReceiver
{
/* Called for each tuple to be output: */
bool (*receiveSlot) (TupleTableSlot *slot,
DestReceiver *self);//接收Slot的函式指標
/* Per-executor-run initialization and shutdown: */
void (*rStartup) (DestReceiver *self,
int operation,
TupleDesc typeinfo);//Startup函式指標
void (*rShutdown) (DestReceiver *self);//Shutdown函式指標
/* Destroy the receiver object itself (if dynamically allocated) */
void (*rDestroy) (DestReceiver *self);//Destroy函式指標
/* CommandDest code for this receiver */
CommandDest mydest;//
/* Private fields might appear beyond this point... */
};
/* ----------------
* CommandDest is a simplistic means of identifying the desired
* destination. Someday this will probably need to be improved.
*
* Note: only the values DestNone, DestDebug, DestRemote are legal for the
* global variable whereToSendOutput. The other values may be used
* as the destination for individual commands.
* ----------------
*/
typedef enum
{
DestNone, /* results are discarded */
DestDebug, /* results go to debugging output */
DestRemote, /* results sent to frontend process */
DestRemoteExecute, /* sent to frontend, in Execute command */
DestRemoteSimple, /* sent to frontend, w/no catalog access */
DestSPI, /* results sent to SPI manager */
DestTuplestore, /* results sent to Tuplestore */
DestIntoRel, /* results sent to relation (SELECT INTO) */
DestCopyOut, /* results sent to COPY TO code */
DestSQLFunction, /* results sent to SQL-language func mgr */
DestTransientRel, /* results sent to transient relation */
DestTupleQueue /* results sent to tuple queue */
} CommandDest;
3、ResetPerTupleExprContext
//重置per-output-tuple exprcontext
/* Reset an EState's per-output-tuple exprcontext, if one's been created */
#define ResetPerTupleExprContext(estate) \
do { \
if ((estate)->es_per_tuple_exprcontext) \
ResetExprContext((estate)->es_per_tuple_exprcontext); \
} while (0)
依賴的函式
1、EnterParallelMode
//進入並行模式函式以及其相關的資料結構/子函式等
/*
* EnterParallelMode
*/
void
EnterParallelMode(void)
{
TransactionState s = CurrentTransactionState;
Assert(s->parallelModeLevel >= 0);
++s->parallelModeLevel;
}
/*
* transaction state structure
*/
typedef struct TransactionStateData
{
TransactionId transactionId; /* my XID, or Invalid if none */
SubTransactionId subTransactionId; /* my subxact ID */
char *name; /* savepoint name, if any */
int savepointLevel; /* savepoint level */
TransState state; /* low-level state */
TBlockState blockState; /* high-level state */
int nestingLevel; /* transaction nesting depth */
int gucNestLevel; /* GUC context nesting depth */
MemoryContext curTransactionContext; /* my xact-lifetime context */
ResourceOwner curTransactionOwner; /* my query resources */
TransactionId *childXids; /* subcommitted child XIDs, in XID order */
int nChildXids; /* # of subcommitted child XIDs */
int maxChildXids; /* allocated size of childXids[] */
Oid prevUser; /* previous CurrentUserId setting */
int prevSecContext; /* previous SecurityRestrictionContext */
bool prevXactReadOnly; /* entry-time xact r/o state */
bool startedInRecovery; /* did we start in recovery? */
bool didLogXid; /* has xid been included in WAL record? */
int parallelModeLevel; /* Enter/ExitParallelMode counter */
struct TransactionStateData *parent; /* back link to parent */
} TransactionStateData;
typedef TransactionStateData *TransactionState;
/*
* transaction states - transaction state from server perspective
*/
typedef enum TransState
{
TRANS_DEFAULT, /* idle */
TRANS_START, /* transaction starting */
TRANS_INPROGRESS, /* inside a valid transaction */
TRANS_COMMIT, /* commit in progress */
TRANS_ABORT, /* abort in progress */
TRANS_PREPARE /* prepare in progress */
} TransState;
/*
* transaction block states - transaction state of client queries
*
* Note: the subtransaction states are used only for non-topmost
* transactions; the others appear only in the topmost transaction.
*/
typedef enum TBlockState
{
/* not-in-transaction-block states */
TBLOCK_DEFAULT, /* idle */
TBLOCK_STARTED, /* running single-query transaction */
/* transaction block states */
TBLOCK_BEGIN, /* starting transaction block */
TBLOCK_INPROGRESS, /* live transaction */
TBLOCK_IMPLICIT_INPROGRESS, /* live transaction after implicit BEGIN */
TBLOCK_PARALLEL_INPROGRESS, /* live transaction inside parallel worker */
TBLOCK_END, /* COMMIT received */
TBLOCK_ABORT, /* failed xact, awaiting ROLLBACK */
TBLOCK_ABORT_END, /* failed xact, ROLLBACK received */
TBLOCK_ABORT_PENDING, /* live xact, ROLLBACK received */
TBLOCK_PREPARE, /* live xact, PREPARE received */
/* subtransaction states */
TBLOCK_SUBBEGIN, /* starting a subtransaction */
TBLOCK_SUBINPROGRESS, /* live subtransaction */
TBLOCK_SUBRELEASE, /* RELEASE received */
TBLOCK_SUBCOMMIT, /* COMMIT received while TBLOCK_SUBINPROGRESS */
TBLOCK_SUBABORT, /* failed subxact, awaiting ROLLBACK */
TBLOCK_SUBABORT_END, /* failed subxact, ROLLBACK received */
TBLOCK_SUBABORT_PENDING, /* live subxact, ROLLBACK received */
TBLOCK_SUBRESTART, /* live subxact, ROLLBACK TO received */
TBLOCK_SUBABORT_RESTART /* failed subxact, ROLLBACK TO received */
} TBlockState;
typedef struct MemoryContextMethods
{
void *(*alloc) (MemoryContext context, Size size);
/* call this free_p in case someone #define's free() */
void (*free_p) (MemoryContext context, void *pointer);
void *(*realloc) (MemoryContext context, void *pointer, Size size);
void (*reset) (MemoryContext context);
void (*delete_context) (MemoryContext context);
Size (*get_chunk_space) (MemoryContext context, void *pointer);
bool (*is_empty) (MemoryContext context);
void (*stats) (MemoryContext context,
MemoryStatsPrintFunc printfunc, void *passthru,
MemoryContextCounters *totals);
#ifdef MEMORY_CONTEXT_CHECKING
void (*check) (MemoryContext context);
#endif
} MemoryContextMethods;
/*
* A memory context can have callback functions registered on it. Any such
* function will be called once just before the context is next reset or
* deleted. The MemoryContextCallback struct describing such a callback
* typically would be allocated within the context itself, thereby avoiding
* any need to manage it explicitly (the reset/delete action will free it).
*/
typedef void (*MemoryContextCallbackFunction) (void *arg);
typedef struct MemoryContextCallback
{
MemoryContextCallbackFunction func; /* function to call */
void *arg; /* argument to pass it */
struct MemoryContextCallback *next; /* next in list of callbacks */
} MemoryContextCallback;
typedef struct MemoryContextData
{
NodeTag type; /* identifies exact kind of context */
/* these two fields are placed here to minimize alignment wastage: */
bool isReset; /* T = no space alloced since last reset */
bool allowInCritSection; /* allow palloc in critical section */
const MemoryContextMethods *methods; /* virtual function table */
MemoryContext parent; /* NULL if no parent (toplevel context) */
MemoryContext firstchild; /* head of linked list of children */
MemoryContext prevchild; /* previous child of same parent */
MemoryContext nextchild; /* next child of same parent */
const char *name; /* context name (just for debugging) */
const char *ident; /* context ID if any (just for debugging) */
MemoryContextCallback *reset_cbs; /* list of reset/delete callbacks */
} MemoryContextData;
/* utils/palloc.h contains typedef struct MemoryContextData *MemoryContext */
/*
* Type MemoryContextData is declared in nodes/memnodes.h. Most users
* of memory allocation should just treat it as an abstract type, so we
* do not provide the struct contents here.
*/
typedef struct MemoryContextData *MemoryContext;
/*
* ResourceOwner objects look like this
*/
typedef struct ResourceOwnerData
{
ResourceOwner parent; /* NULL if no parent (toplevel owner) */
ResourceOwner firstchild; /* head of linked list of children */
ResourceOwner nextchild; /* next child of same parent */
const char *name; /* name (just for debugging) */
/* We have built-in support for remembering: */
ResourceArray bufferarr; /* owned buffers */
ResourceArray catrefarr; /* catcache references */
ResourceArray catlistrefarr; /* catcache-list pins */
ResourceArray relrefarr; /* relcache references */
ResourceArray planrefarr; /* plancache references */
ResourceArray tupdescarr; /* tupdesc references */
ResourceArray snapshotarr; /* snapshot references */
ResourceArray filearr; /* open temporary files */
ResourceArray dsmarr; /* dynamic shmem segments */
ResourceArray jitarr; /* JIT contexts */
/* We can remember up to MAX_RESOWNER_LOCKS references to local locks. */
int nlocks; /* number of owned locks */
LOCALLOCK *locks[MAX_RESOWNER_LOCKS]; /* list of owned locks */
} ResourceOwnerData;
/*
* ResourceOwner objects are an opaque data structure known only within
* resowner.c.
*/
typedef struct ResourceOwnerData *ResourceOwner;
typedef uint32 TransactionId;
2、ExecShutdownNode
//關閉資源
/*
* ExecShutdownNode
*
* Give execution nodes a chance to stop asynchronous resource consumption
* and release any resources still held. Currently, this is only used for
* parallel query, but we might want to extend it to other cases also (e.g.
* FDW). We might also want to call it sooner, as soon as it's evident that
* no more rows will be needed (e.g. when a Limit is filled) rather than only
* at the end of ExecutorRun.
*/
bool
ExecShutdownNode(PlanState *node)
{
if (node == NULL)
return false;
check_stack_depth();
planstate_tree_walker(node, ExecShutdownNode, NULL);
/*
* Treat the node as running while we shut it down, but only if it's run
* at least once already. We don't expect much CPU consumption during
* node shutdown, but in the case of Gather or Gather Merge, we may shut
* down workers at this stage. If so, their buffer usage will get
* propagated into pgBufferUsage at this point, and we want to make sure
* that it gets associated with the Gather node. We skip this if the node
* has never been executed, so as to avoid incorrectly making it appear
* that it has.
*/
if (node->instrument && node->instrument->running)
InstrStartNode(node->instrument);
switch (nodeTag(node))
{
case T_GatherState:
ExecShutdownGather((GatherState *) node);
break;
case T_ForeignScanState:
ExecShutdownForeignScan((ForeignScanState *) node);
break;
case T_CustomScanState:
ExecShutdownCustomScan((CustomScanState *) node);
break;
case T_GatherMergeState:
ExecShutdownGatherMerge((GatherMergeState *) node);
break;
case T_HashState:
ExecShutdownHash((HashState *) node);
break;
case T_HashJoinState:
ExecShutdownHashJoin((HashJoinState *) node);
break;
default:
break;
}
/* Stop the node if we started it above, reporting 0 tuples. */
if (node->instrument && node->instrument->running)
InstrStopNode(node->instrument, 0);
return false;
}
3、ExitParallelMode
//退出並行模式
/*
* ExitParallelMode
*/
void
ExitParallelMode(void)
{
TransactionState s = CurrentTransactionState;
Assert(s->parallelModeLevel > 0);
Assert(s->parallelModeLevel > 1 || !ParallelContextActive());
--s->parallelModeLevel;
}
二、原始碼解讀
/* ----------------------------------------------------------------
* ExecutePlan
*
* Processes the query plan until we have retrieved 'numberTuples' tuples,
* moving in the specified direction.
*
* Runs to completion if numberTuples is 0
*
* Note: the ctid attribute is a 'junk' attribute that is removed before the
* user can see it
* ----------------------------------------------------------------
*/
/*
輸入：
estate-Executor狀態資訊
planstate-執行計劃狀態資訊
user_parallel_mode-是否使用並行模式
operation-操作型別
sendTuples-是否需要傳輸Tuples
numberTuples-需要返回的Tuples數
direction-掃描方向
dest-目標接收器指標
execute_once-是否只執行一次？
輸出：
*/
static void
ExecutePlan(EState *estate,
PlanState *planstate,
bool use_parallel_mode,
CmdType operation,
bool sendTuples,
uint64 numberTuples,
ScanDirection direction,
DestReceiver *dest,
bool execute_once)
{
TupleTableSlot *slot;//儲存Tuple的Slot
uint64 current_tuple_count;//Tuple計數器
/*
* initialize local variables
*/
current_tuple_count = 0;//初始化
/*
* Set the direction.
*/
estate->es_direction = direction;//掃描方向
/*
* If the plan might potentially be executed multiple times, we must force
* it to run without parallelism, because we might exit early.
*/
if (!execute_once)
use_parallel_mode = false;//不使用並行模式
estate->es_use_parallel_mode = use_parallel_mode;
if (use_parallel_mode)
EnterParallelMode();//如果並行執行，進入並行模式
/*
* Loop until we've processed the proper number of tuples from the plan.
*/
for (;;)
{
/* Reset the per-output-tuple exprcontext */
ResetPerTupleExprContext(estate);//重置 per-output-tuple exprcontext
/*
* Execute the plan and obtain a tuple
*/
slot = ExecProcNode(planstate);//執行處理單元
/*
* if the tuple is null, then we assume there is nothing more to
* process so we just end the loop...
*/
if (TupIsNull(slot))
{
/* Allow nodes to release or shut down resources. */
(void) ExecShutdownNode(planstate);//如果slot返回為空，已完成處理，可以釋放資源了
break;
}
/*
* If we have a junk filter, then project a new tuple with the junk
* removed.
*
* Store this new "clean" tuple in the junkfilter's resultSlot.
* (Formerly, we stored it back over the "dirty" tuple, which is WRONG
* because that tuple slot has the wrong descriptor.)
*/
if (estate->es_junkFilter != NULL)
slot = ExecFilterJunk(estate->es_junkFilter, slot);//去掉“無價值”的屬性
/*
* If we are supposed to send the tuple somewhere, do so. (In
* practice, this is probably always the case at this point.)
*/
if (sendTuples)//如果需要傳輸結果集
{
/*
* If we are not able to send the tuple, we assume the destination
* has closed and no more tuples can be sent. If that's the case,
* end the loop.
*/
if (!dest->receiveSlot(slot, dest))//傳輸，如果接收完成，則退出
break;
}
/*
* Count tuples processed, if this is a SELECT. (For other operation
* types, the ModifyTable plan node must count the appropriate
* events.)
*/
if (operation == CMD_SELECT)
(estate->es_processed)++;//統計計數
/*
* check our tuple count.. if we've processed the proper number then
* quit, else loop again and process more tuples. Zero numberTuples
* means no limit.
*/
current_tuple_count++;//統計返回的Tuple數
if (numberTuples && numberTuples == current_tuple_count)
{
/* Allow nodes to release or shut down resources. */
(void) ExecShutdownNode(planstate);//釋放資源後退出迴圈
break;
}
}
if (use_parallel_mode)
ExitParallelMode();//退出並行模式
}
三、跟蹤分析
插入測試資料：
testdb=# -- #7 ExecutePlan
testdb=# -- 獲取pid
testdb=# select pg_backend_pid();
pg_backend_pid
----------------
3294
(1 row)
testdb=# -- 插入1行
testdb=# insert into t_insert values(15,'ExecutePlan','ExecutePlan','ExecutePlan');
(掛起)
啟動gdb，跟蹤除錯：
[root@localhost ~]# gdb -p 3294
GNU gdb (GDB) Red Hat Enterprise Linux 7.6.1-100.el7
Copyright (C) 2013 Free Software Foundation, Inc.
...
(gdb) b ExecutePlan
Breakpoint 1 at 0x692df1: file execMain.c, line 1697.
(gdb) c
Continuing.
Breakpoint 1, ExecutePlan (estate=0x2cca440, planstate=0x2cca790, use_parallel_mode=false, operation=CMD_INSERT, sendTuples=false, numberTuples=0, direction=ForwardScanDirection, dest=0x2cd0888,
execute_once=true) at execMain.c:1697
1697 current_tuple_count = 0;
(gdb)
#檢視輸入引數
#1、Executor狀態 estate
(gdb) p *estate
$1 = {type = T_EState, es_direction = ForwardScanDirection, es_snapshot = 0x2c3f920, es_crosscheck_snapshot = 0x0, es_range_table = 0x2cd0768, es_plannedstmt = 0x2c1d478,
es_sourceText = 0x2c1bef0 "insert into t_insert values(15,'ExecutePlan','ExecutePlan','ExecutePlan');", es_junkFilter = 0x0, es_output_cid = 0, es_result_relations = 0x2cca680,
es_num_result_relations = 1, es_result_relation_info = 0x0, es_root_result_relations = 0x0, es_num_root_result_relations = 0, es_tuple_routing_result_relations = 0x0, es_trig_target_relations = 0x0,
es_trig_tuple_slot = 0x2ccb750, es_trig_oldtup_slot = 0x0, es_trig_newtup_slot = 0x0, es_param_list_info = 0x0, es_param_exec_vals = 0x2cca650, es_queryEnv = 0x0, es_query_cxt = 0x2cca330,
es_tupleTable = 0x2ccb000, es_rowMarks = 0x0, es_processed = 0, es_lastoid = 0, es_top_eflags = 0, es_instrument = 0, es_finished = false, es_exprcontexts = 0x2ccac50, es_subplanstates = 0x0,
es_auxmodifytables = 0x0, es_per_tuple_exprcontext = 0x0, es_epqTuple = 0x0, es_epqTupleSet = 0x0, es_epqScanDone = 0x0, es_use_parallel_mode = false, es_query_dsa = 0x0, es_jit_flags = 0,
es_jit = 0x0}
#執行期間構造的snapshot
(gdb) p *(estate->es_snapshot)
$2 = {satisfies = 0x9f73fc <HeapTupleSatisfiesMVCC>, xmin = 1612872, xmax = 1612872, xip = 0x0, xcnt = 0, subxip = 0x0, subxcnt = 0, suboverflowed = false, takenDuringRecovery = false, copied = true,
curcid = 0, speculativeToken = 0, active_count = 1, regd_count = 2, ph_node = {first_child = 0xe7bac0 <CatalogSnapshotData+64>, next_sibling = 0x0, prev_or_parent = 0x0}, whenTaken = 0, lsn = 0}
(gdb)
#執行計劃對應的Statement
#commandType = CMD_INSERT，插入操作
#hasReturning =false，沒有返回值
(gdb) p *(estate->es_range_table)
$3 = {type = T_List, length = 1, head = 0x2cd0748, tail = 0x2cd0748}
(gdb) p *(estate->es_plannedstmt)
$4 = {type = T_PlannedStmt, commandType = CMD_INSERT, queryId = 0, hasReturning = false, hasModifyingCTE = false, canSetTag = true, transientPlan = false, dependsOnRole = false,
parallelModeNeeded = false, jitFlags = 0, planTree = 0x2c1cff8, rtable = 0x2cd0768, resultRelations = 0x2cd0808, nonleafResultRelations = 0x0, rootResultRelations = 0x0, subplans = 0x0,
rewindPlanIDs = 0x0, rowMarks = 0x0, relationOids = 0x2cd07b8, invalItems = 0x0, paramExecTypes = 0x2c43698, utilityStmt = 0x0, stmt_location = 0, stmt_len = 73}
(gdb)
#SQL語句
#es_sourceText = 0x2c1bef0 "insert into t_insert values(15,'ExecutePlan','ExecutePlan','ExecutePlan');"
#junkFilter為NULL(0x0)
#結果Relation相關資訊
(gdb) p *(estate->es_result_relations)
$5 = {type = T_ResultRelInfo, ri_RangeTableIndex = 1, ri_RelationDesc = 0x7f3c13f49b78, ri_NumIndices = 1, ri_IndexRelationDescs = 0x2ccafd0, ri_IndexRelationInfo = 0x2ccafe8, ri_TrigDesc = 0x0,
ri_TrigFunctions = 0x0, ri_TrigWhenExprs = 0x0, ri_TrigInstrument = 0x0, ri_FdwRoutine = 0x0, ri_FdwState = 0x0, ri_usesFdwDirectModify = false, ri_WithCheckOptions = 0x0,
ri_WithCheckOptionExprs = 0x0, ri_ConstraintExprs = 0x0, ri_junkFilter = 0x0, ri_returningList = 0x0, ri_projectReturning = 0x0, ri_onConflictArbiterIndexes = 0x0, ri_onConflict = 0x0,
ri_PartitionCheck = 0x0, ri_PartitionCheckExpr = 0x0, ri_PartitionRoot = 0x0, ri_PartitionReadyForRouting = false}
#es_trig_tuple_slot
gdb) p *(estate->es_trig_tuple_slot)
$6 = {type = T_TupleTableSlot, tts_isempty = true, tts_shouldFree = false, tts_shouldFreeMin = false, tts_slow = false, tts_tuple = 0x0, tts_tupleDescriptor = 0x0, tts_mcxt = 0x2cca330,
tts_buffer = 0, tts_nvalid = 0, tts_values = 0x0, tts_isnull = 0x0, tts_mintuple = 0x0, tts_minhdr = {t_len = 0, t_self = {ip_blkid = {bi_hi = 0, bi_lo = 0}, ip_posid = 0}, t_tableOid = 0,
t_data = 0x0}, tts_off = 0, tts_fixedTupleDescriptor = false}
#estate中的其他變數
(gdb) p *(estate->es_param_exec_vals)
$7 = {execPlan = 0x0, value = 0, isnull = false}
(gdb) p *(estate->es_query_cxt)
$8 = {type = T_AllocSetContext, isReset = false, allowInCritSection = false, methods = 0xb8c720 <AllocSetMethods>, parent = 0x2c3f3d0, firstchild = 0x2ccc340, prevchild = 0x0, nextchild = 0x0,
name = 0xb1a840 "ExecutorState", ident = 0x0, reset_cbs = 0x0}
(gdb) p *(estate->es_tupleTable)
$9 = {type = T_List, length = 3, head = 0x2ccb240, tail = 0x2ccb7e0}
(gdb) p *(estate->es_exprcontexts)
$10 = {type = T_List, length = 1, head = 0x2ccafb0, tail = 0x2ccafb0}
#2、planstate
(gdb) p *planstate
$14 = {type = T_ModifyTableState, plan = 0x2c1cff8, state = 0x2cca440, ExecProcNode = 0x69a78b <ExecProcNodeFirst>, ExecProcNodeReal = 0x6c2485 <ExecModifyTable>, instrument = 0x0,
worker_instrument = 0x0, qual = 0x0, lefttree = 0x0, righttree = 0x0, initPlan = 0x0, subPlan = 0x0, chgParam = 0x0, ps_ResultTupleSlot = 0x2ccb6a0, ps_ExprContext = 0x0, ps_ProjInfo = 0x0,
scandesc = 0x0}
#plan
(gdb) p *(planstate->plan)
$15 = {type = T_ModifyTable, startup_cost = 0, total_cost = 0.01, plan_rows = 1, plan_width = 298, parallel_aware = false, parallel_safe = false, plan_node_id = 0, targetlist = 0x0, qual = 0x0,
lefttree = 0x0, righttree = 0x0, initPlan = 0x0, extParam = 0x0, allParam = 0x0}
#PlanState中的EState
(gdb) p *(planstate->state)
$16 = {type = T_EState, es_direction = ForwardScanDirection, es_snapshot = 0x2c3f920, es_crosscheck_snapshot = 0x0, es_range_table = 0x2cd0768, es_plannedstmt = 0x2c1d478,
es_sourceText = 0x2c1bef0 "insert into t_insert values(15,'ExecutePlan','ExecutePlan','ExecutePlan');", es_junkFilter = 0x0, es_output_cid = 0, es_result_relations = 0x2cca680,
es_num_result_relations = 1, es_result_relation_info = 0x0, es_root_result_relations = 0x0, es_num_root_result_relations = 0, es_tuple_routing_result_relations = 0x0, es_trig_target_relations = 0x0,
es_trig_tuple_slot = 0x2ccb750, es_trig_oldtup_slot = 0x0, es_trig_newtup_slot = 0x0, es_param_list_info = 0x0, es_param_exec_vals = 0x2cca650, es_queryEnv = 0x0, es_query_cxt = 0x2cca330,
es_tupleTable = 0x2ccb000, es_rowMarks = 0x0, es_processed = 0, es_lastoid = 0, es_top_eflags = 0, es_instrument = 0, es_finished = false, es_exprcontexts = 0x2ccac50, es_subplanstates = 0x0,
es_auxmodifytables = 0x0, es_per_tuple_exprcontext = 0x0, es_epqTuple = 0x0, es_epqTupleSet = 0x0, es_epqScanDone = 0x0, es_use_parallel_mode = false, es_query_dsa = 0x0, es_jit_flags = 0,
es_jit = 0x0}
#ExecProcNode=ExecProcNodeFirst
#ExecProcNodeReal =ExecModifyTable
#3、use_parallel_mode
(gdb) p use_parallel_mode
$17 = false #非並行模式
#4、operation
(gdb) p operation
$18 = CMD_INSERT #插入操作
#5、sendTuples
(gdb) p sendTuples
$19 = false
#6、numberTuples
(gdb) p numberTuples
$20 = 0
#7、direction
(gdb) p direction
$21 = ForwardScanDirection
#8、dest
(gdb) p *dest
$22 = {receiveSlot = 0x4857ad <printtup>, rStartup = 0x485196 <printtup_startup>, rShutdown = 0x485bad <printtup_shutdown>, rDestroy = 0x485c21 <printtup_destroy>, mydest = DestRemote}
#9、execute_once
(gdb) p execute_once
$23 = true
#----------------------------------------------------
#繼續執行
(gdb) next
1702 estate->es_direction = direction;
(gdb)
1708 if (!execute_once)
(gdb)
1711 estate->es_use_parallel_mode = use_parallel_mode;
(gdb)
1712 if (use_parallel_mode)
(gdb)
1721 ResetPerTupleExprContext(estate);
(gdb)
1726 slot = ExecProcNode(planstate);
(gdb)
1732 if (TupIsNull(slot))
(gdb) p *slot
Cannot access memory at address 0x0
#返回的slot為NULL
(gdb) next
1735 (void) ExecShutdownNode(planstate);
(gdb)
1736 break;
(gdb)
1787 if (use_parallel_mode)
(gdb)
1789 }
(gdb)
standard_ExecutorRun (queryDesc=0x2c3f4e0, direction=ForwardScanDirection, count=0, execute_once=true) at execMain.c:377
377 if (sendTuples)
#DONE!
四、小結
1、統一的處理模型：先前也提過，INSERT/UPDATE/DELETE/SELECT等，均採用統一的處理模式進行處理；
2、重要的資料結構：PlanState和EState，在整個執行過程中，非常重要的狀態資訊；
3、並行模式：並行模式的處理，看起來只是開啟&開啟，後續值得探究一番。
來自 “ ITPUB部落格 ” ，連結：http://blog.itpub.net/6906/viewspace-2374908/，如需轉載，請註明出處，否則將追究法律責任。
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