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。
typedef struct ModifyTable
{
Plan plan;
CmdType operation;
bool canSetTag;
Index nominalRelation;
Index rootRelation;
bool partColsUpdated;
List *resultRelations;
int resultRelIndex;
int rootResultRelIndex;
List *plans;
List *withCheckOptionLists;
List *returningLists;
List *fdwPrivLists;
Bitmapset *fdwDirectModifyPlans;
List *rowMarks;
int epqParam;
OnConflictAction onConflictAction;
List *arbiterIndexes;
List *onConflictSet;
Node *onConflictWhere;
Index exclRelRTI;
List *exclRelTlist;
} 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。
typedef struct ResultRelInfo
{
NodeTag type;
//RTE索引
Index ri_RangeTableIndex;
//结果/目标relation的描述符
Relation ri_RelationDesc;
//目标关系中索引数目
int ri_NumIndices;
//索引的关系描述符数组(索引视为一个relation)
RelationPtr ri_IndexRelationDescs;
//索引的键/属性数组
IndexInfo **ri_IndexRelationInfo;
//触发的索引
TriggerDesc *ri_TrigDesc;
//触发器函数(缓存)
FmgrInfo *ri_TrigFunctions;
//WHEN表达式状态的触发器数组
ExprState **ri_TrigWhenExprs;
//可选的触发器运行期度量器
Instrumentation *ri_TrigInstrument;
//FDW回调函数
struct FdwRoutine *ri_FdwRoutine;
//可用于存储FDW的私有状态
void *ri_FdwState;
//直接更新FDW时为T
bool ri_usesFdwDirectModify;
//WithCheckOption链表
List *ri_WithCheckOptions;
//WithCheckOption表达式链表
List *ri_WithCheckOptionExprs;
//约束检查表达式状态数组
ExprState **ri_ConstraintExprs;
//用于从元组中删除junk属性
JunkFilter *ri_junkFilter;
//RETURNING表达式链表
List *ri_returningList;
//用于计算RETURNING链表
ProjectionInfo *ri_projectReturning;
//用于检查冲突的仲裁器索引的列表
List *ri_onConflictArbiterIndexes;
//ON CONFLICT解析状态
OnConflictSetState *ri_onConflict;
//分区检查表达式链表
List *ri_PartitionCheck;
//分区检查表达式状态
ExprState *ri_PartitionCheckExpr;
//分区root根表描述符
Relation ri_PartitionRoot;
//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。
typedef struct PartitionRoutingInfo
{
TupleConversionMap *pi_RootToPartitionMap;
TupleConversionMap *pi_PartitionToRootMap;
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;
TupleDesc outdesc;
AttrNumber *attrMap;
Datum *invalues;
bool *inisnull; //是否为NULL标记数组
Datum *outvalues;
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.
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)
{
//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);
//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
{
//扁平列,直接从堆元组中提取值
datum = slot_getattr(slot, keycol, &isNull);
}
else
{
//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");
}
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];
}
static inline void
slot_getsomeattrs(TupleTableSlot *slot, int attnum)
{
if (slot->tts_nvalid < attnum)
slot_getsomeattrs_int(slot, attnum);
}
void
slot_getsomeattrs_int(TupleTableSlot *slot, int attnum)
{
//检查调用者输入参数是否有误
Assert(slot->tts_nvalid < attnum);
Assert(attnum > 0);
//attnum参数判断
if (unlikely(attnum > slot->tts_tupleDescriptor->natts))
elog(ERROR, "invalid attribute number %d", attnum);
//从元组中获取尽可能多的属性。
slot->tts_ops->getsomeattrs(slot, attnum);
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！
