PostgreSQL中获取Tuple的分区键值函数是什么

这篇文章主要介绍"PostgreSQL中获取Tuple的分区键值函数是什么"，在日常操作中，相信很多人在PostgreSQL中获取Tuple的分区键值函数是什么问题上存在疑惑，小编查阅了各式资料，整理出简单好用的操作方法，希望对大家解答"PostgreSQL中获取Tuple的分区键值函数是什么"的疑惑有所帮助！接下来，请跟着小编一起来学习吧！

一、数据结构

ModifyTable
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T    bool        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

FormPartitionKeyDatum函数获取Tuple的分区键值,返回键值values[]数组和是否为null标记isnull[]数组.

/* ---------------- *      FormPartitionKeyDatum *          Construct values[] and isnull[] arrays for the partition key *          of a tuple. *          构造values[]数组和isnull[]数组 * *  pd              Partition dispatch object of the partitioned table *  pd              分区表的分区分发器(dispatch)对象 * *  slot            Heap tuple from which to extract partition key *  slot            从其中提前分区键的heap tuple * *  estate          executor state for evaluating any partition key *                  expressions (must be non-NULL) *  estate          解析分区键表达式(必须非NULL)的执行器状态 * *  values          Array of partition key Datums (output area) *                  分区键Datums数组(输出参数) *  isnull          Array of is-null indicators (output area) *                  is-null标记数组(输出参数) * * the ecxt_scantuple slot of estate's per-tuple expr context must point to * the heap tuple passed in. * estate的per-tuple上下文的ecxt_scantuple必须指向传入的heap tuple * ---------------- */static voidFormPartitionKeyDatum(PartitionDispatch pd,                      TupleTableSlot *slot,                      EState *estate,                      Datum *values,                      bool *isnull){    ListCell   *partexpr_item;    int         i;    if (pd->key->partexprs != NIL && pd->keystate == NIL)    {        /* Check caller has set up context correctly */        //检查调用者是否已正确配置内存上下文        Assert(estate != NULL &&               GetPerTupleExprContext(estate)->ecxt_scantuple == slot);        /* First time through, set up expression evaluation state */        //第一次进入,配置表达式解析器状态        pd->keystate = ExecPrepareExprList(pd->key->partexprs, estate);    }    partexpr_item = list_head(pd->keystate);//获取分区键表达式状态    for (i = 0; i < pd->key->partnatts; i++)//循环遍历分区键    {        AttrNumber  keycol = pd->key->partattrs[i];//分区键属性编号        Datum       datum;// typedef uintptr_t Datum;sizeof(Datum) == sizeof(void *) == 4 or 8        bool        isNull;//是否null        if (keycol != 0)//编号不为0        {            /* Plain column; get the value directly from the heap tuple */            //扁平列,直接从堆元组中提取值            datum = slot_getattr(slot, keycol, &isNull);        }        else        {            /* Expression; need to evaluate it */            //表达式,需要解析            if (partexpr_item == NULL)//分区键表达式状态为NULL,报错                elog(ERROR, "wrong number of partition key expressions");            //获取表达式值            datum = ExecEvalExprSwitchContext((ExprState *) lfirst(partexpr_item),                                              GetPerTupleExprContext(estate),                                              &isNull);            //切换至下一个            partexpr_item = lnext(partexpr_item);        }        values[i] = datum;//赋值        isnull[i] = isNull;    }    if (partexpr_item != NULL)//参数设置有误?报错        elog(ERROR, "wrong number of partition key expressions");}/* * slot_getattr - fetch one attribute of the slot's contents. * slot_getattr - 提取slot中的某个属性值 */static inline Datumslot_getattr(TupleTableSlot *slot, int attnum,             bool *isnull){    AssertArg(attnum > 0);    if (attnum > slot->tts_nvalid)        slot_getsomeattrs(slot, attnum);    *isnull = slot->tts_isnull[attnum - 1];    return slot->tts_values[attnum - 1];}/* * This function forces the entries of the slot's Datum/isnull arrays to be * valid at least up through the attnum'th entry. * 这个函数强制slot的Datum/isnull数组的条目至少在attnum的第一个条目上是有效的。 */static inline voidslot_getsomeattrs(TupleTableSlot *slot, int attnum){    if (slot->tts_nvalid < attnum)        slot_getsomeattrs_int(slot, attnum);}/* * slot_getsomeattrs_int - workhorse for slot_getsomeattrs() * slot_getsomeattrs_int - slot_getsomeattrs()函数的实际实现 */voidslot_getsomeattrs_int(TupleTableSlot *slot, int attnum){    /* Check for caller errors */    //检查调用者输入参数是否有误    Assert(slot->tts_nvalid < attnum); /* slot_getsomeattr checked */    Assert(attnum > 0);    //attnum参数判断    if (unlikely(attnum > slot->tts_tupleDescriptor->natts))        elog(ERROR, "invalid attribute number %d", attnum);    /* Fetch as many attributes as possible from the underlying tuple. */    //从元组中获取尽可能多的属性。    slot->tts_ops->getsomeattrs(slot, attnum);    /*     * If the underlying tuple doesn't have enough attributes, tuple descriptor     * must have the missing attributes.     * 如果底层元组没有足够的属性，那么元组描述符必须具有缺少的属性。     */    if (unlikely(slot->tts_nvalid < attnum))    {        slot_getmissingattrs(slot, slot->tts_nvalid, attnum);        slot->tts_nvalid = attnum;    }}

三、跟踪分析

测试脚本如下

-- Hash Partitiondrop 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);insert into t_hash_partition(c1,c2,c3) VALUES(20,'HASH0','HAHS0');

启动gdb,设置断点

(gdb) b FormPartitionKeyDatumBreakpoint 5 at 0x6e30d2: file execPartition.c, line 1087.(gdb) b slot_getattrBreakpoint 6 at 0x489d9b: file heaptuple.c, line 1510.(gdb) cContinuing.Breakpoint 5, FormPartitionKeyDatum (pd=0x2e1bfa0, slot=0x2e1b8a0, estate=0x2e1aeb8, values=0x7fff4e2407a0,     isnull=0x7fff4e240780) at execPartition.c:10871087        if (pd->key->partexprs != NIL && pd->keystate == NIL)

循环,根据分区键获取相应的键值

1087        if (pd->key->partexprs != NIL && pd->keystate == NIL)(gdb) n1097        partexpr_item = list_head(pd->keystate);(gdb) 1098        for (i = 0; i < pd->key->partnatts; i++)(gdb) 1100            AttrNumber  keycol = pd->key->partattrs[i];(gdb) 1104            if (keycol != 0)(gdb) 1107                datum = slot_getattr(slot, keycol, &isNull);

进入函数slot_getattr

(gdb) stepBreakpoint 6, slot_getattr (slot=0x2e1b8a0, attnum=1, isnull=0x7fff4e240735) at heaptuple.c:15101510        HeapTuple   tuple = slot->tts_tuple;

获取结果,分区键值为20

...(gdb) p *isnull$31 = false(gdb) p slot->tts_values[attnum - 1]$32 = 20

返回到FormPartitionKeyDatum函数中

(gdb) n1593    }(gdb) FormPartitionKeyDatum (pd=0x2e1bfa0, slot=0x2e1b8a0, estate=0x2e1aeb8, values=0x7fff4e2407a0, isnull=0x7fff4e240780)    at execPartition.c:11191119            values[i] = datum;

完成调用

1119            values[i] = datum;(gdb) n1120            isnull[i] = isNull;(gdb) 1098        for (i = 0; i < pd->key->partnatts; i++)(gdb) 1123        if (partexpr_item != NULL)(gdb) 1125    }(gdb) ExecFindPartition (resultRelInfo=0x2e1b108, pd=0x2e1c5b8, slot=0x2e1b8a0, estate=0x2e1aeb8) at execPartition.c:282282         if (partdesc->nparts == 0)

到此，关于"PostgreSQL中获取Tuple的分区键值函数是什么"的学习就结束了，希望能够解决大家的疑惑。理论与实践的搭配能更好的帮助大家学习，快去试试吧！若想继续学习更多相关知识，请继续关注网站，小编会继续努力为大家带来更多实用的文章！