两学一做网站无法做题/广告优化师工作内容

在PG中,分区表通过"继承"的方式实现,这里就会存在一个问题,就是在插入数据时,PG如何确定数据应该插入到哪个目标分区?在PG中,通过函数ExecPrepareTupleRouting为路由待插入的元组做准备,主要的目的是确定元组所在的分区。

一、数据结构

ModifyTable
ModifyTable Node
通过插入、更新或删除，将子计划生成的行应用到结果表。

/* ----------------*   ModifyTable node -*      Apply rows produced by subplan(s) to result table(s),*      by inserting, updating, or deleting.*      通过插入、更新或删除，将子计划生成的行应用到结果表。** If the originally named target table is a partitioned table, both* nominalRelation and rootRelation contain the RT index of the partition* root, which is not otherwise mentioned in the plan.  Otherwise rootRelation* is zero.  However, nominalRelation will always be set, as it's the rel that* EXPLAIN should claim is the INSERT/UPDATE/DELETE target.* 如果最初命名的目标表是分区表，则nominalRelation和rootRelation都包含分区根的RT索引，计划中没有另外提到这个索引。* 否则，根关系为零。但是，总是会设置名义关系，nominalRelation因为EXPLAIN应该声明的rel是INSERT/UPDATE/DELETE目标关系。* * Note that rowMarks and epqParam are presumed to be valid for all the* subplan(s); they can't contain any info that varies across subplans.* 注意，rowMarks和epqParam被假定对所有子计划有效;* 它们不能包含任何在子计划中变化的信息。* ----------------*/
typedef struct ModifyTable
{Plan        plan;CmdType     operation;      /* 操作类型;INSERT, UPDATE, or DELETE */bool        canSetTag;      /* 是否需要设置tag?do we set the command tag/es_processed? */Index       nominalRelation;    /* 用于EXPLAIN的父RT索引;Parent RT index for use of EXPLAIN */Index       rootRelation;   /* 根Root RT索引(如目标为分区表);Root RT index, if target is partitioned */bool        partColsUpdated;    /* 更新了层次结构中的分区关键字;some part key in hierarchy updated */List       *resultRelations;    /* RT索引的整型链表;integer list of RT indexes */int         resultRelIndex; /* 计划链表中第一个resultRel的索引;index of first resultRel in plan's list */int         rootResultRelIndex; /* 分区表根索引;index of the partitioned table root */List       *plans;          /* 生成源数据的计划链表;plan(s) producing source data */List       *withCheckOptionLists;   /* 每一个目标表均具备的WCO链表;per-target-table WCO lists */List       *returningLists; /* 每一个目标表均具备的RETURNING链表;per-target-table RETURNING tlists */List       *fdwPrivLists;   /* 每一个目标表的FDW私有数据链表;per-target-table FDW private data lists */Bitmapset  *fdwDirectModifyPlans;   /* FDW DM计划索引位图;indices of FDW DM plans */List       *rowMarks;       /* rowMarks链表;PlanRowMarks (non-locking only) */int         epqParam;       /* EvalPlanQual再解析使用的参数ID;ID of Param for EvalPlanQual re-eval */OnConflictAction onConflictAction;  /* ON CONFLICT action */List       *arbiterIndexes; /* 冲突仲裁器索引表;List of ON CONFLICT arbiter index OIDs  */List       *onConflictSet;  /* SET for INSERT ON CONFLICT DO UPDATE */Node       *onConflictWhere;    /* WHERE for ON CONFLICT UPDATE */Index       exclRelRTI;     /* RTI of the EXCLUDED pseudo relation */List       *exclRelTlist;   /* 已排除伪关系的投影列链表;tlist of the EXCLUDED pseudo relation */
} ModifyTable;

ResultRelInfo
ResultRelInfo结构体
每当更新一个现有的关系时，我们必须更新关系上的索引，也许还需要触发触发器。ResultRelInfo保存关于结果关系所需的所有信息，包括索引。

/** ResultRelInfo* ResultRelInfo结构体** Whenever we update an existing relation, we have to update indexes on the* relation, and perhaps also fire triggers.  ResultRelInfo holds all the* information needed about a result relation, including indexes.* 每当更新一个现有的关系时，我们必须更新关系上的索引，也许还需要触发触发器。* ResultRelInfo保存关于结果关系所需的所有信息，包括索引。* * Normally, a ResultRelInfo refers to a table that is in the query's* range table; then ri_RangeTableIndex is the RT index and ri_RelationDesc* is just a copy of the relevant es_relations[] entry.  But sometimes,* in ResultRelInfos used only for triggers, ri_RangeTableIndex is zero* and ri_RelationDesc is a separately-opened relcache pointer that needs* to be separately closed.  See ExecGetTriggerResultRel.* 通常，ResultRelInfo是指查询范围表中的表;* ri_RangeTableIndex是RT索引，而ri_RelationDesc只是相关es_relations[]条目的副本。* 但有时，在只用于触发器的ResultRelInfos中，ri_RangeTableIndex为零(NULL)，*   而ri_RelationDesc是一个需要单独关闭单独打开的relcache指针。*   具体可参考ExecGetTriggerResultRel结构体。*/
typedef struct ResultRelInfo
{NodeTag     type;/* result relation's range table index, or 0 if not in range table *///RTE索引Index       ri_RangeTableIndex;/* relation descriptor for result relation *///结果/目标relation的描述符Relation    ri_RelationDesc;/* # of indices existing on result relation *///目标关系中索引数目int         ri_NumIndices;/* array of relation descriptors for indices *///索引的关系描述符数组(索引视为一个relation)RelationPtr ri_IndexRelationDescs;/* array of key/attr info for indices *///索引的键/属性数组IndexInfo **ri_IndexRelationInfo;/* triggers to be fired, if any *///触发的索引TriggerDesc *ri_TrigDesc;/* cached lookup info for trigger functions *///触发器函数(缓存)FmgrInfo   *ri_TrigFunctions;/* array of trigger WHEN expr states *///WHEN表达式状态的触发器数组ExprState **ri_TrigWhenExprs;/* optional runtime measurements for triggers *///可选的触发器运行期度量器Instrumentation *ri_TrigInstrument;/* FDW callback functions, if foreign table *///FDW回调函数struct FdwRoutine *ri_FdwRoutine;/* available to save private state of FDW *///可用于存储FDW的私有状态void       *ri_FdwState;/* true when modifying foreign table directly *///直接更新FDW时为Tbool        ri_usesFdwDirectModify;/* list of WithCheckOption's to be checked *///WithCheckOption链表List       *ri_WithCheckOptions;/* list of WithCheckOption expr states *///WithCheckOption表达式链表List       *ri_WithCheckOptionExprs;/* array of constraint-checking expr states *///约束检查表达式状态数组ExprState **ri_ConstraintExprs;/* for removing junk attributes from tuples *///用于从元组中删除junk属性JunkFilter *ri_junkFilter;/* list of RETURNING expressions *///RETURNING表达式链表List       *ri_returningList;/* for computing a RETURNING list *///用于计算RETURNING链表ProjectionInfo *ri_projectReturning;/* list of arbiter indexes to use to check conflicts *///用于检查冲突的仲裁器索引的列表List       *ri_onConflictArbiterIndexes;/* ON CONFLICT evaluation state *///ON CONFLICT解析状态OnConflictSetState *ri_onConflict;/* partition check expression *///分区检查表达式链表List       *ri_PartitionCheck;/* partition check expression state *///分区检查表达式状态ExprState  *ri_PartitionCheckExpr;/* relation descriptor for root partitioned table *///分区root根表描述符Relation    ri_PartitionRoot;/* Additional information specific to partition tuple routing *///额外的分区元组路由信息struct PartitionRoutingInfo *ri_PartitionInfo;
} ResultRelInfo;

PartitionRoutingInfo
PartitionRoutingInfo结构体
分区路由信息,用于将元组路由到表分区的结果关系信息。

/** PartitionRoutingInfo* PartitionRoutingInfo - 分区路由信息* * Additional result relation information specific to routing tuples to a* table partition.* 用于将元组路由到表分区的结果关系信息。*/
typedef struct PartitionRoutingInfo
{/** Map for converting tuples in root partitioned table format into* partition format, or NULL if no conversion is required.* 映射，用于将根分区表格式的元组转换为分区格式，如果不需要转换，则转换为NULL。*/TupleConversionMap *pi_RootToPartitionMap;/** Map for converting tuples in partition format into the root partitioned* table format, or NULL if no conversion is required.* 映射，用于将分区格式的元组转换为根分区表格式，如果不需要转换，则转换为NULL。*/TupleConversionMap *pi_PartitionToRootMap;/** Slot to store tuples in partition format, or NULL when no translation* is required between root and partition.* 以分区格式存储元组的slot.在根分区和分区之间不需要转换时为NULL。*/TupleTableSlot *pi_PartitionTupleSlot;
} PartitionRoutingInfo;

TupleConversionMap
TupleConversionMap结构体,用于存储元组转换映射信息.

typedef struct TupleConversionMap
{TupleDesc   indesc;         /* 源行类型的描述符;tupdesc for source rowtype */TupleDesc   outdesc;        /* 结果行类型的描述符;tupdesc for result rowtype */AttrNumber *attrMap;        /* 输入字段的索引信息,0表示NULL;indexes of input fields, or 0 for null */Datum      *invalues;       /* 析构源数据的工作空间;workspace for deconstructing source */bool       *inisnull;       //是否为NULL标记数组Datum      *outvalues;      /* 构造结果的工作空间;workspace for constructing result */bool       *outisnull;      //null标记
} TupleConversionMap;

二、源码解读

ExecPrepareTupleRouting函数确定要插入slot中的tuple所属的分区，同时修改mtstate和estate等相关信息,为后续实际的插入作准备。

/** ExecPrepareTupleRouting --- prepare for routing one tuple* ExecPrepareTupleRouting --- 为路由一个元组做准备* * Determine the partition in which the tuple in slot is to be inserted,* and modify mtstate and estate to prepare for it.* 确定要插入slot中tuple的分区，并修改mtstate和estate以为插入作准备。** Caller must revert the estate changes after executing the insertion!* In mtstate, transition capture changes may also need to be reverted.* 调用方必须在执行插入之后恢复estate中被修改的属性值!* 在mtstate中，转换捕获更改也可能需要恢复。** Returns a slot holding the tuple of the partition rowtype.* 返回包含分区rowtype元组的槽位。*/
static TupleTableSlot *
ExecPrepareTupleRouting(ModifyTableState *mtstate,EState *estate,PartitionTupleRouting *proute,ResultRelInfo *targetRelInfo,TupleTableSlot *slot)
{ModifyTable *node;//ModifyTable节点int         partidx;//分区索引ResultRelInfo *partrel;//ResultRelInfo结构体指针(数组)HeapTuple   tuple;//元组/** Determine the target partition.  If ExecFindPartition does not find a* partition after all, it doesn't return here; otherwise, the returned* value is to be used as an index into the arrays for the ResultRelInfo* and TupleConversionMap for the partition.* 确定目标分区。* 如果ExecFindPartition最终没有找到分区，它不会在这里返回;* 否则，返回值将用作分区的ResultRelInfo和TupleConversionMap数组的索引。*/partidx = ExecFindPartition(targetRelInfo,proute->partition_dispatch_info,slot,estate);Assert(partidx >= 0 && partidx < proute->num_partitions);/** Get the ResultRelInfo corresponding to the selected partition; if not* yet there, initialize it.* 获取与所选分区对应的ResultRelInfo;如果还没有，则初始化。*/partrel = proute->partitions[partidx];if (partrel == NULL)partrel = ExecInitPartitionInfo(mtstate, targetRelInfo,proute, estate,partidx);/** Check whether the partition is routable if we didn't yet* 检查分区是否可路由* * Note: an UPDATE of a partition key invokes an INSERT that moves the* tuple to a new partition.  This check would be applied to a subplan* partition of such an UPDATE that is chosen as the partition to route* the tuple to.  The reason we do this check here rather than in* ExecSetupPartitionTupleRouting is to avoid aborting such an UPDATE* unnecessarily due to non-routable subplan partitions that may not be* chosen for update tuple movement after all.* 注意:分区键的更新调用将元组移动到新分区的插入。* 此检查将应用于此类更新的子计划分区，该分区被选择为将元组路由到的分区。* 在这里而不是在ExecSetupPartitionTupleRouting中执行此检查的原因是为了避免由于无法路由的子计划分区而不必要地中止这样的更新，这些分区可能最终不会被选择用于更新元组移动。*/if (!partrel->ri_PartitionReadyForRouting){/* Verify the partition is a valid target for INSERT. *///验证分区是否可用于INSERTCheckValidResultRel(partrel, CMD_INSERT);/* Set up information needed for routing tuples to the partition. *///设置将元组路由到分区所需的信息。ExecInitRoutingInfo(mtstate, estate, proute, partrel, partidx);}/** Make it look like we are inserting into the partition.* 让它看起来像是插入到分区中。*/estate->es_result_relation_info = partrel;/* Get the heap tuple out of the given slot. *///从给定的slot中获取heap tupletuple = ExecMaterializeSlot(slot);/** If we're capturing transition tuples, we might need to convert from the* partition rowtype to parent rowtype.* 如果正在捕获转换元组，可能需要将分区行类型转换为根分区表的行类型。*/if (mtstate->mt_transition_capture != NULL){if (partrel->ri_TrigDesc &&partrel->ri_TrigDesc->trig_insert_before_row){/** If there are any BEFORE triggers on the partition, we'll have* to be ready to convert their result back to tuplestore format.* 如果分区上有BEFORE触发器，必须准备将它们的结果转换回tuplestore格式。*/mtstate->mt_transition_capture->tcs_original_insert_tuple = NULL;mtstate->mt_transition_capture->tcs_map =TupConvMapForLeaf(proute, targetRelInfo, partidx);}else{/** Otherwise, just remember the original unconverted tuple, to* avoid a needless round trip conversion.* 否则，只需记住原始的未转换元组，以避免不必要的来回转换。*/mtstate->mt_transition_capture->tcs_original_insert_tuple = tuple;mtstate->mt_transition_capture->tcs_map = NULL;}}if (mtstate->mt_oc_transition_capture != NULL){mtstate->mt_oc_transition_capture->tcs_map =TupConvMapForLeaf(proute, targetRelInfo, partidx);}/** Convert the tuple, if necessary.* 如需要,转换元组*/ConvertPartitionTupleSlot(proute->parent_child_tupconv_maps[partidx],tuple,proute->partition_tuple_slot,&slot);/* Initialize information needed to handle ON CONFLICT DO UPDATE. *///如为ON CONFLICT DO UPDATE模式,则初始化相关信息Assert(mtstate != NULL);node = (ModifyTable *) mtstate->ps.plan;if (node->onConflictAction == ONCONFLICT_UPDATE){Assert(mtstate->mt_existing != NULL);ExecSetSlotDescriptor(mtstate->mt_existing,RelationGetDescr(partrel->ri_RelationDesc));Assert(mtstate->mt_conflproj != NULL);ExecSetSlotDescriptor(mtstate->mt_conflproj,partrel->ri_onConflict->oc_ProjTupdesc);}return slot;
}/** ExecFetchSlotHeapTuple - fetch HeapTuple representing the slot's content* ExecFetchSlotHeapTuple - 根据slot提取HeapTuple** The returned HeapTuple represents the slot's content as closely as* possible.* 返回的HeapTuple尽可能就是slot的内容。* * If materialize is true, the contents of the slots will be made independent* from the underlying storage (i.e. all buffer pins are release, memory is* allocated in the slot's context).* 如果materialize为T，slot的内容将独立于底层存储(即释放所有缓冲区pin，在slot的上下文中分配内存)。** If shouldFree is not-NULL it'll be set to true if the returned tuple has* been allocated in the calling memory context, and must be freed by the* caller (via explicit pfree() or a memory context reset).* 如果shouldFree not-NULL，那么如果返回的元组已经在调用内存上下文中分配，*   并且必须由调用方释放(通过显式pfree()或内存上下文重置)。** NB: If materialize is true, modifications of the returned tuple are* allowed. But it depends on the type of the slot whether such modifications* will also affect the slot's contents. While that is not the nicest* behaviour, all such modifcations are in the process of being removed.* 注意:如果materialize为T，则允许修改返回的元组。* 但这取决于slot的类型，这种修改是否也会影响slot的内容。* 虽然这不是最好的行为，但所有这些修改都在被移除的过程中。*/
HeapTuple
ExecFetchSlotHeapTuple(TupleTableSlot *slot, bool materialize, bool *shouldFree)
{/** sanity checks* 安全检查*/Assert(slot != NULL);Assert(!TTS_EMPTY(slot));/* Materialize the tuple so that the slot "owns" it, if requested. *///物化元组，以便slot“拥有”它(如要求)。if (materialize)slot->tts_ops->materialize(slot);if (slot->tts_ops->get_heap_tuple == NULL){if (shouldFree)*shouldFree = true;return slot->tts_ops->copy_heap_tuple(slot);//返回slot拷贝}else{if (shouldFree)*shouldFree = false;return slot->tts_ops->get_heap_tuple(slot);//直接返回slot}
}

三、跟踪分析

测试脚本如下

-- Hash Partition
drop table if exists t_hash_partition;
create table t_hash_partition (c1 int not null,c2  varchar(40),c3 varchar(40)) partition by hash(c1);
create table t_hash_partition_1 partition of t_hash_partition for values with (modulus 6,remainder 0);
create table t_hash_partition_2 partition of t_hash_partition for values with (modulus 6,remainder 1);
create table t_hash_partition_3 partition of t_hash_partition for values with (modulus 6,remainder 2);
create table t_hash_partition_4 partition of t_hash_partition for values with (modulus 6,remainder 3);
create table t_hash_partition_5 partition of t_hash_partition for values with (modulus 6,remainder 4);
create table t_hash_partition_6 partition of t_hash_partition for values with (modulus 6,remainder 5);-- delete from t_hash_partition where c1 = 0;
insert into t_hash_partition(c1,c2,c3) VALUES(0,'HASH0','HAHS0');

启动gdb,设置断点,进入ExecPrepareTupleRouting

(gdb) b ExecPrepareTupleRouting
Breakpoint 1 at 0x710b1e: file nodeModifyTable.c, line 1712.
(gdb) c
Continuing.Breakpoint 1, ExecPrepareTupleRouting (mtstate=0x1e4de60, estate=0x1e4daf8, proute=0x1e4eb48, targetRelInfo=0x1e4dd48, slot=0x1e4e4e0) at nodeModifyTable.c:1712
1712        partidx = ExecFindPartition(targetRelInfo,

查看函数调用栈
ExecPrepareTupleRouting在ExecModifyTable Node中被调用,为后续的插入作准备.

(gdb) bt
#0  ExecPrepareTupleRouting (mtstate=0x1e4de60, estate=0x1e4daf8, proute=0x1e4eb48, targetRelInfo=0x1e4dd48, slot=0x1e4e4e0)at nodeModifyTable.c:1712
#1  0x0000000000711602 in ExecModifyTable (pstate=0x1e4de60) at nodeModifyTable.c:2157
#2  0x00000000006e4c30 in ExecProcNodeFirst (node=0x1e4de60) at execProcnode.c:445
#3  0x00000000006d9974 in ExecProcNode (node=0x1e4de60) at ../../../src/include/executor/executor.h:237
#4  0x00000000006dc22d in ExecutePlan (estate=0x1e4daf8, planstate=0x1e4de60, use_parallel_mode=false, operation=CMD_INSERT, sendTuples=false, numberTuples=0, direction=ForwardScanDirection, dest=0x1e67e90, execute_once=true) at execMain.c:1723
#5  0x00000000006d9f5c in standard_ExecutorRun (queryDesc=0x1e39d68, direction=ForwardScanDirection, count=0, execute_once=true) at execMain.c:364
#6  0x00000000006d9d7f in ExecutorRun (queryDesc=0x1e39d68, direction=ForwardScanDirection, count=0, execute_once=true)at execMain.c:307
#7  0x00000000008cbdb3 in ProcessQuery (plan=0x1e67d18, sourceText=0x1d60ec8 "insert into t_hash_partition(c1,c2,c3) VALUES(0,'HASH0','HAHS0');", params=0x0, queryEnv=0x0, dest=0x1e67e90, completionTag=0x7ffdcf148b20 "") at pquery.c:161
#8  0x00000000008cd6f9 in PortalRunMulti (portal=0x1dc6538, isTopLevel=true, setHoldSnapshot=false, dest=0x1e67e90, altdest=0x1e67e90, completionTag=0x7ffdcf148b20 "") at pquery.c:1286
#9  0x00000000008cccb9 in PortalRun (portal=0x1dc6538, count=9223372036854775807, isTopLevel=true, run_once=true, dest=0x1e67e90, altdest=0x1e67e90, completionTag=0x7ffdcf148b20 "") at pquery.c:799
#10 0x00000000008c6b1e in exec_simple_query (query_string=0x1d60ec8 "insert into t_hash_partition(c1,c2,c3) VALUES(0,'HASH0','HAHS0');") at postgres.c:1145
#11 0x00000000008cae70 in PostgresMain (argc=1, argv=0x1d8aba8, dbname=0x1d8aa10 "testdb", username=0x1d5dba8 "xdb")at postgres.c:4182

找到该元组所在的分区

(gdb) n
1716        Assert(partidx >= 0 && partidx < proute->num_partitions);
(gdb) p partidx
$1 = 2

获取与所选分区对应的ResultRelInfo;如果还没有，则初始化

(gdb) n
1722        partrel = proute->partitions[partidx];
(gdb) 
1723        if (partrel == NULL)
(gdb) p *partrel
Cannot access memory at address 0x0
(gdb) n
1724            partrel = ExecInitPartitionInfo(mtstate, targetRelInfo,    

初始化后的partrel

(gdb) p *partrel
$2 = {type = T_ResultRelInfo, ri_RangeTableIndex = 1, ri_RelationDesc = 0x1e7c940, ri_NumIndices = 0, ri_IndexRelationDescs = 0x0, ri_IndexRelationInfo = 0x0, 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 = 0x1e4f538, ri_PartitionCheckExpr = 0x0, ri_PartitionRoot = 0x1e7c2f8, ri_PartitionReadyForRouting = true}

目标分区描述符-->t_hash_partition_3

(gdb) p *partrel->ri_RelationDesc
$3 = {rd_node = {spcNode = 1663, dbNode = 16402, relNode = 16995}, rd_smgr = 0x1e34510, rd_refcnt = 1, rd_backend = -1, rd_islocaltemp = false, rd_isnailed = false, rd_isvalid = true, rd_indexvalid = 0 '\000', rd_statvalid = false, rd_createSubid = 0, rd_newRelfilenodeSubid = 0, rd_rel = 0x1e7c1e0, rd_att = 0x1e7cb58, rd_id = 16995, rd_lockInfo = {lockRelId = {relId = 16995, dbId = 16402}}, rd_rules = 0x0, rd_rulescxt = 0x0, trigdesc = 0x0, rd_rsdesc = 0x0, rd_fkeylist = 0x0, rd_fkeyvalid = false, rd_partkeycxt = 0x0, rd_partkey = 0x0, rd_pdcxt = 0x0, rd_partdesc = 0x0, rd_partcheck = 0x1e7aa30, rd_indexlist = 0x0, rd_oidindex = 0, rd_pkindex = 0, rd_replidindex = 0, rd_statlist = 0x0, rd_indexattr = 0x0, rd_projindexattr = 0x0, rd_keyattr = 0x0, rd_pkattr = 0x0, rd_idattr = 0x0, rd_projidx = 0x0, rd_pubactions = 0x0, rd_options = 0x0, rd_index = 0x0, rd_indextuple = 0x0, rd_amhandler = 0, rd_indexcxt = 0x0, rd_amroutine = 0x0, rd_opfamily = 0x0, rd_opcintype = 0x0, rd_support = 0x0, rd_supportinfo = 0x0, rd_indoption = 0x0, rd_indexprs = 0x0, rd_indpred = 0x0, rd_exclops = 0x0, rd_exclprocs = 0x0, rd_exclstrats = 0x0, rd_amcache = 0x0, rd_indcollation = 0x0, rd_fdwroutine = 0x0, rd_toastoid = 0, pgstat_info = 0x1de40b0}
------------------
testdb=# select oid,relname from pg_class where oid=16995;oid  |      relname       
-------+--------------------16995 | t_hash_partition_3
(1 row)  
----------------- 

该分区是可路由的

(gdb) p partrel->ri_PartitionReadyForRouting
$4 = true

设置estate变量(让它看起来像是插入到分区中)/物化tuple

(gdb) n
1751        estate->es_result_relation_info = partrel;
(gdb) 
1754        tuple = ExecMaterializeSlot(slot);
(gdb) 
1760        if (mtstate->mt_transition_capture != NULL)
(gdb) p tuple
$5 = (HeapTuple) 0x1e4f4e0
(gdb) p *tuple
$6 = {t_len = 40, t_self = {ip_blkid = {bi_hi = 65535, bi_lo = 65535}, ip_posid = 0}, t_tableOid = 0, t_data = 0x1e4f4f8}
(gdb) 
(gdb) p *tuple->t_data
$7 = {t_choice = {t_heap = {t_xmin = 160, t_xmax = 4294967295, t_field3 = {t_cid = 2249, t_xvac = 2249}}, t_datum = {datum_len_ = 160, datum_typmod = -1, datum_typeid = 2249}}, t_ctid = {ip_blkid = {bi_hi = 65535, bi_lo = 65535}, ip_posid = 0}, t_infomask2 = 3, t_infomask = 2, t_hoff = 24 '\030', t_bits = 0x1e4f50f ""}

mtstate->mt_transition_capture 为NULL,无需处理相关信息

(gdb) p mtstate->mt_transition_capture 
$8 = (struct TransitionCaptureState *) 0x0
1783        if (mtstate->mt_oc_transition_capture != NULL)
(gdb) 

如需要,转换元组

1792        ConvertPartitionTupleSlot(proute->parent_child_tupconv_maps[partidx],
(gdb) 
1798        Assert(mtstate != NULL);
(gdb) 
1799        node = (ModifyTable *) mtstate->ps.plan;
(gdb) p *mtstate
$9 = {ps = {type = T_ModifyTableState, plan = 0x1e59838, state = 0x1e4daf8, ExecProcNode = 0x711056 <ExecModifyTable>, ExecProcNodeReal = 0x711056 <ExecModifyTable>, instrument = 0x0, worker_instrument = 0x0, worker_jit_instrument = 0x0, qual = 0x0, lefttree = 0x0, righttree = 0x0, initPlan = 0x0, subPlan = 0x0, chgParam = 0x0, ps_ResultTupleSlot = 0x1e4ede8, ps_ExprContext = 0x0, ps_ProjInfo = 0x0, scandesc = 0x0}, operation = CMD_INSERT, canSetTag = true, mt_done = false, mt_plans = 0x1e4e078, mt_nplans = 1, mt_whichplan = 0, resultRelInfo = 0x1e4dd48, rootResultRelInfo = 0x0, mt_arowmarks = 0x1e4e098, mt_epqstate = {estate = 0x0, planstate = 0x0, origslot = 0x1e4e4e0, plan = 0x1e59588, arowMarks = 0x0, epqParam = 0}, fireBSTriggers = false, mt_existing = 0x0, mt_excludedtlist = 0x0, mt_conflproj = 0x0, mt_partition_tuple_routing = 0x1e4eb48, mt_transition_capture = 0x0, mt_oc_transition_capture = 0x0, mt_per_subplan_tupconv_maps = 0x0}  

返回slot,完成调用

(gdb) n
1800        if (node->onConflictAction == ONCONFLICT_UPDATE)
(gdb) 
1810        return slot;
(gdb) 
1811    }

DONE!
ExecFindPartition函数是主要的实现函数,下节再行介绍

四、参考资料

PG 11.1 Source Code.
注: doxygen上的源代码与PG 11.1源代码并不一致,本节基于11.1进行分析.