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 void FormPartitionKeyDatum(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 Datum slot_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 void slot_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 */ void slot_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 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); insert into t_hash_partition(c1,c2,c3) VALUES(20,'HASH0','HAHS0');
启动gdb,设置断点
(gdb) b FormPartitionKeyDatum Breakpoint 5 at 0x6e30d2: file execPartition.c, line 1087. (gdb) b slot_getattr Breakpoint 6 at 0x489d9b: file heaptuple.c, line 1510. (gdb) c Continuing. Breakpoint 5, FormPartitionKeyDatum (pd=0x2e1bfa0, slot=0x2e1b8a0, estate=0x2e1aeb8, values=0x7fff4e2407a0, isnull=0x7fff4e240780) at execPartition.c:1087 1087 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) n 1097 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) step Breakpoint 6, slot_getattr (slot=0x2e1b8a0, attnum=1, isnull=0x7fff4e240735) at heaptuple.c:1510 1510 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) n 1593 } (gdb) FormPartitionKeyDatum (pd=0x2e1bfa0, slot=0x2e1b8a0, estate=0x2e1aeb8, values=0x7fff4e2407a0, isnull=0x7fff4e240780) at execPartition.c:1119 1119 values[i] = datum;
完成调用
1119 values[i] = datum; (gdb) n 1120 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:282 282 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,请继续关注亿速云网站,小编会继续努力为大家带来更多实用的文章!
原创文章,作者:kepupublish,如若转载,请注明出处:https://blog.ytso.com/tech/database/205015.html