PostgreSQL 源码解读（94）- 分区表#2（数据插入路由#2）
本节介绍了ExecPrepareTupleRouting->ExecFindPartition函数，该函数为heap tuple找到合适的分区。
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
ExecFindPartition函数在以父节点为根的分区树中为包含在*slot中的元组找到目标分区(叶子分区)
/*
* ExecFindPartition -- Find a leaf partition in the partition tree rooted
* at parent, for the heap tuple contained in *slot
* ExecFindPartition —— 在以父节点为根的分区树中为包含在*slot中的堆元组找到目标分区(叶子分区)
*
* estate must be non-NULL; we'll need it to compute any expressions in the
* partition key(s)
* estate不能为NULL;需要使用它计算分区键上的表达式
*
* If no leaf partition is found, this routine errors out with the appropriate
* error message, else it returns the leaf partition sequence number
* as an index into the array of (ResultRelInfos of) all leaf partitions in
* the partition tree.
* 如果没有找到目标分区，则此例程将输出适当的错误消息，
* 否则它将分区树中所有叶子分区的数组(ResultRelInfos)的目标分区序列号作为索引返回。
*/
int
ExecFindPartition(ResultRelInfo *resultRelInfo, PartitionDispatch *pd,
TupleTableSlot *slot, EState *estate)
{
int result;//结果索引号
Datum values[PARTITION_MAX_KEYS];//值类型Datum
bool isnull[PARTITION_MAX_KEYS];//是否null?
Relation rel;//关系
PartitionDispatch dispatch;//
ExprContext *ecxt = GetPerTupleExprContext(estate);//表达式上下文
TupleTableSlot *ecxt_scantuple_old = ecxt->ecxt_scantuple;//原tuple slot
TupleTableSlot *myslot = NULL;//临时变量
MemoryContext oldcxt;//原内存上下文
HeapTuple tuple;//tuple
/* use per-tuple context here to avoid leaking memory */
//使用每个元组上下文来避免内存泄漏
oldcxt = MemoryContextSwitchTo(GetPerTupleMemoryContext(estate));
/*
* First check the root table's partition constraint, if any. No point in
* routing the tuple if it doesn't belong in the root table itself.
* 首先检查根表的分区约束(如果有的话)。如果元组不属于根表本身，则没有必要路由它。
*/
if (resultRelInfo->ri_PartitionCheck)
ExecPartitionCheck(resultRelInfo, slot, estate, true);
/* start with the root partitioned table */
//从root分区表开始
tuple = ExecFetchSlotTuple(slot);//获取tuple
dispatch = pd[0];//root
while (true)
{
PartitionDesc partdesc;//分区描述符
TupleConversionMap *map = dispatch->tupmap;//转换映射
int cur_index = -1;//当前索引
rel = dispatch->reldesc;//relation
partdesc = RelationGetPartitionDesc(rel);//获取rel描述符
/*
* Convert the tuple to this parent's layout, if different from the
* current relation.
* 如果元组与当前关系不同，则将tuple转换为parent's layout。
*/
myslot = dispatch->tupslot;
if (myslot != NULL && map != NULL)
{
tuple = do_convert_tuple(tuple, map);
ExecStoreTuple(tuple, myslot, InvalidBuffer, true);
slot = myslot;
}
/*
* Extract partition key from tuple. Expression evaluation machinery
* that FormPartitionKeyDatum() invokes expects ecxt_scantuple to
* point to the correct tuple slot. The slot might have changed from
* what was used for the parent table if the table of the current
* partitioning level has different tuple descriptor from the parent.
* So update ecxt_scantuple accordingly.
* 从元组中提取分区键。
* FormPartitionKeyDatum()调用的表达式计算机制期望ecxt_scantuple指向正确的元组slot。
* 如果当前分区级别的表与父表具有不同的元组描述符，那么slot可能已经改变了父表使用的slot。
* 因此相应地更新ecxt_scantuple。
*/
ecxt->ecxt_scantuple = slot;
FormPartitionKeyDatum(dispatch, slot, estate, values, isnull);
/*
* Nothing for get_partition_for_tuple() to do if there are no
* partitions to begin with.
* 如无分区,则退出(无需调用get_partition_for_tuple)
*/
if (partdesc->nparts == 0)
{
result = -1;
break;
}
//调用get_partition_for_tuple
cur_index = get_partition_for_tuple(rel, values, isnull);
/*
* cur_index < 0 means we failed to find a partition of this parent.
* cur_index >= 0 means we either found the leaf partition, or the
* next parent to find a partition of.
* cur_index < 0表示未能找到该父节点的分区。
* cur_index >= 0表示要么找到叶子分区，要么找到下一个父分区。
*/
if (cur_index < 0)
{
result = -1;
break;//找不到,退出
}
else if (dispatch->indexes[cur_index] >= 0)
{
result = dispatch->indexes[cur_index];
/* success! */
break;//找到了,退出循环
}
else
{
/* move down one level */
//移到下一层查找
dispatch = pd[-dispatch->indexes[cur_index]];
/*
* Release the dedicated slot, if it was used. Create a copy of
* the tuple first, for the next iteration.
*/
if (slot == myslot)
{
tuple = ExecCopySlotTuple(myslot);
ExecClearTuple(myslot);
}
}
}
/* Release the tuple in the lowest parent's dedicated slot. */
//释放位于最低父级的专用的slot相对应的元组。
if (slot == myslot)
ExecClearTuple(myslot);
/* A partition was not found. */
//找不到partition
if (result < 0)
{
char *val_desc;
val_desc = ExecBuildSlotPartitionKeyDescription(rel,
values, isnull, 64);
Assert(OidIsValid(RelationGetRelid(rel)));
ereport(ERROR,
(errcode(ERRCODE_CHECK_VIOLATION),
errmsg("no partition of relation \"%s\" found for row",
RelationGetRelationName(rel)),
val_desc ? errdetail("Partition key of the failing row contains %s.", val_desc) : 0));
}
MemoryContextSwitchTo(oldcxt);
ecxt->ecxt_scantuple = ecxt_scantuple_old;
return result;
}
/*
* get_partition_for_tuple
* Finds partition of relation which accepts the partition key specified
* in values and isnull
* get_partition_for_tuple
* 查找参数为values和isnull中指定分区键的关系分区
*
* Return value is index of the partition (>= 0 and < partdesc->nparts) if one
* found or -1 if none found.
* 返回值是分区的索引(>= 0和< partdesc->nparts)，
* 如果找到一个分区，则返回值;如果没有找到，则返回值为-1。
*/
static int
get_partition_for_tuple(Relation relation, Datum *values, bool *isnull)
{
int bound_offset;
int part_index = -1;
PartitionKey key = RelationGetPartitionKey(relation);
PartitionDesc partdesc = RelationGetPartitionDesc(relation);
PartitionBoundInfo boundinfo = partdesc->boundinfo;
/* Route as appropriate based on partitioning strategy. */
//基于分区的策略进行路由
switch (key->strategy)
{
case PARTITION_STRATEGY_HASH://HASH分区
{
int greatest_modulus;
uint64 rowHash;
greatest_modulus = get_hash_partition_greatest_modulus(boundinfo);
rowHash = compute_partition_hash_value(key->partnatts,
key->partsupfunc,
values, isnull);
part_index = boundinfo->indexes[rowHash % greatest_modulus];
}
break;
case PARTITION_STRATEGY_LIST://列表分区
if (isnull[0])
{
if (partition_bound_accepts_nulls(boundinfo))
part_index = boundinfo->null_index;
}
else
{
bool equal = false;
bound_offset = partition_list_bsearch(key->partsupfunc,
key->partcollation,
boundinfo,
values[0], &equal);
if (bound_offset >= 0 && equal)
part_index = boundinfo->indexes[bound_offset];
}
break;
case PARTITION_STRATEGY_RANGE://范围分区
{
bool equal = false,
range_partkey_has_null = false;
int i;
/*
* No range includes NULL, so this will be accepted by the
* default partition if there is one, and otherwise rejected.
* 任何范围都不包含NULL值，因此默认分区将接受该值(如果存在)，否则将拒绝该值。
*/
for (i = 0; i < key->partnatts; i++)
{
if (isnull[i])
{
range_partkey_has_null = true;
break;
}
}
if (!range_partkey_has_null)
{
bound_offset = partition_range_datum_bsearch(key->partsupfunc,
key->partcollation,
boundinfo,
key->partnatts,
values,
&equal);
/*
* The bound at bound_offset is less than or equal to the
* tuple value, so the bound at offset+1 is the upper
* bound of the partition we're looking for, if there
* actually exists one.
* bound_offset的边界小于或等于元组值，所以offset+1的边界是我们要找的分区的上界，如存在的话。
*/
part_index = boundinfo->indexes[bound_offset + 1];
}
}
break;
default:
elog(ERROR, "unexpected partition strategy: %d",
(int) key->strategy);//暂不支持其他分区
}
/*
* part_index < 0 means we failed to find a partition of this parent. Use
* the default partition, if there is one.
* part_index < 0表示没有找到这个父节点的分区。如存在分区，则使用默认分区。
*/
if (part_index < 0)
part_index = boundinfo->default_index;
return part_index;
}
依赖的函数
/*
* get_hash_partition_greatest_modulus
*
* Returns the greatest modulus of the hash partition bound. The greatest
* modulus will be at the end of the datums array because hash partitions are
* arranged in the ascending order of their moduli and remainders.
* 返回哈希分区边界的最大模。
* 最大模量将位于datums数组的末尾，因为哈希分区按照它们的模块和余数的升序排列。
*/
int
get_hash_partition_greatest_modulus(PartitionBoundInfo bound)
{
Assert(bound && bound->strategy == PARTITION_STRATEGY_HASH);
Assert(bound->datums && bound->ndatums > 0);
Assert(DatumGetInt32(bound->datums[bound->ndatums - 1][0]) > 0);
return DatumGetInt32(bound->datums[bound->ndatums - 1][0]);
}
/*
* compute_partition_hash_value
*
* Compute the hash value for given partition key values.
* 给定分区键值,计算相应的Hash值
*/
uint64
compute_partition_hash_value(int partnatts, FmgrInfo *partsupfunc,
Datum *values, bool *isnull)
{
int i;
uint64 rowHash = 0;//返回结果
Datum seed = UInt64GetDatum(HASH_PARTITION_SEED);
for (i = 0; i < partnatts; i++)
{
/* Nulls are just ignored */
if (!isnull[i])
{
//不为NULL
Datum hash;
Assert(OidIsValid(partsupfunc[i].fn_oid));
/*
* Compute hash for each datum value by calling respective
* datatype-specific hash functions of each partition key
* attribute.
* 通过调用每个分区键属性的特定于数据类型的哈希函数，计算每个数据值的哈希值。
*/
hash = FunctionCall2(&partsupfunc[i], values[i], seed);
/* Form a single 64-bit hash value */
//组合成一个单独的64bit哈希值
rowHash = hash_combine64(rowHash, DatumGetUInt64(hash));
}
}
return rowHash;
}
/*
* Combine two 64-bit hash values, resulting in another hash value, using the
* same kind of technique as hash_combine(). Testing shows that this also
* produces good bit mixing.
* 使用与hash_combine()相同的技术组合两个64位哈希值，生成另一个哈希值。
* 测试表明，该方法也能产生良好的混合效果。
*/
static inline uint64
hash_combine64(uint64 a, uint64 b)
{
/* 0x49a0f4dd15e5a8e3 is 64bit random data */
a ^= b + UINT64CONST(0x49a0f4dd15e5a8e3) + (a << 54) + (a >> 7);
return a;
}
//两个参数的函数调用宏定义
#define FunctionCall2(flinfo, arg1, arg2) \
FunctionCall2Coll(flinfo, InvalidOid, arg1, arg2)
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(0,'HASH0','HAHS0');
启动gdb,设置断点,进入ExecFindPartition
(gdb) b ExecFindPartition
Breakpoint 1 at 0x6e19e7: file execPartition.c, line 227.
(gdb) c
Continuing.
Breakpoint 1, ExecFindPartition (resultRelInfo=0x14299a8, pd=0x142ae58, slot=0x142a140, estate=0x1429758)
at execPartition.c:227
227 ExprContext *ecxt = GetPerTupleExprContext(estate);
初始化变量,切换内存上下文
227 ExprContext *ecxt = GetPerTupleExprContext(estate);
(gdb) n
228 TupleTableSlot *ecxt_scantuple_old = ecxt->ecxt_scantuple;
(gdb)
229 TupleTableSlot *myslot = NULL;
(gdb)
234 oldcxt = MemoryContextSwitchTo(GetPerTupleMemoryContext(estate));
(gdb) p ecxt_scantuple_old
$1 = (TupleTableSlot *) 0x0
提取tuple,获取dispatch
(gdb) n
244 tuple = ExecFetchSlotTuple(slot);
(gdb)
245 dispatch = pd[0];
(gdb) n
249 TupleConversionMap *map = dispatch->tupmap;
(gdb) p *tuple
$2 = {t_len = 40, t_self = {ip_blkid = {bi_hi = 65535, bi_lo = 65535}, ip_posid = 0}, t_tableOid = 0, t_data = 0x142b158}
(gdb)
查看分发器dispatch信息
(gdb) p *dispatch
$3 = {reldesc = 0x7fbfa6900950, key = 0x1489860, keystate = 0x0, partdesc = 0x149b130, tupslot = 0x0, tupmap = 0x0,
indexes = 0x142ade8}
(gdb) p *dispatch->reldesc
$4 = {rd_node = {spcNode = 1663, dbNode = 16402, relNode = 16986}, rd_smgr = 0x0, 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 = 0x7fbfa6900b68, rd_att = 0x7fbfa6900c80, rd_id = 16986,
rd_lockInfo = {lockRelId = {relId = 16986, dbId = 16402}}, rd_rules = 0x0, rd_rulescxt = 0x0, trigdesc = 0x0,
rd_rsdesc = 0x0, rd_fkeylist = 0x0, rd_fkeyvalid = false, rd_partkeycxt = 0x1489710, rd_partkey = 0x1489860,
rd_pdcxt = 0x149afe0, rd_partdesc = 0x149b130, rd_partcheck = 0x0, 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 = 0x0}
----------------------------------------------------------------------------
testdb=# select relname from pg_class where oid=16986;
relname
------------------
t_hash_partition -->hash分区表
(1 row)
----------------------------------------------------------------------------
(gdb) p *dispatch->key
$5 = {strategy = 104 'h', partnatts = 1, partattrs = 0x14898f8, partexprs = 0x0, partopfamily = 0x1489918,
partopcintype = 0x1489938, partsupfunc = 0x1489958, partcollation = 0x14899b0, parttypid = 0x14899d0,
parttypmod = 0x14899f0, parttyplen = 0x1489a10, parttypbyval = 0x1489a30,
parttypalign = 0x1489a50 "i~\177\177\177\177\177\177\b", parttypcoll = 0x1489a70}
(gdb) p *dispatch->partdesc
$6 = {nparts = 6, oids = 0x149b168, boundinfo = 0x149b1a0}
(gdb) p *dispatch->partdesc->boundinfo
$8 = {strategy = 104 'h', ndatums = 6, datums = 0x149b1f8, kind = 0x0, indexes = 0x149b288, null_index = -1,
default_index = -1}
(gdb) p *dispatch->partdesc->boundinfo->datums
$9 = (Datum *) 0x149b2c0
(gdb) p **dispatch->partdesc->boundinfo->datums
$10 = 6
(gdb) p *dispatch->indexes
$15 = 0
分区描述符中的oids(分别对应t_hash_partition_1->6)
(gdb) p dispatch->partdesc->oids[0]
$11 = 16989
(gdb) p dispatch->partdesc->oids[1]
$12 = 16992
...
(gdb) p dispatch->partdesc->oids[5]
$13 = 17004
索引信息
(gdb) p dispatch->indexes[0]
$16 = 0
...
(gdb) p dispatch->indexes[5]
$18 = 5
设置当前索引(-1),获取relation信息,获取分区描述符
(gdb) n
250 int cur_index = -1;
(gdb)
252 rel = dispatch->reldesc;
(gdb)
253 partdesc = RelationGetPartitionDesc(rel);
(gdb)
259 myslot = dispatch->tupslot;
(gdb) p *partdesc
$19 = {nparts = 6, oids = 0x149b168, boundinfo = 0x149b1a0}
(gdb)
myslot为NULL
(gdb) n
260 if (myslot != NULL && map != NULL)
(gdb) p myslot
$20 = (TupleTableSlot *) 0x0
从元组中提取分区键
(gdb) n
275 ecxt->ecxt_scantuple = slot;
(gdb)
276 FormPartitionKeyDatum(dispatch, slot, estate, values, isnull);
(gdb)
282 if (partdesc->nparts == 0)
(gdb) p *partdesc
$21 = {nparts = 6, oids = 0x149b168, boundinfo = 0x149b1a0}
(gdb) p *slot
$22 = {type = T_TupleTableSlot, tts_isempty = false, tts_shouldFree = true, tts_shouldFreeMin = false, tts_slow = false,
tts_tuple = 0x142b140, tts_tupleDescriptor = 0x1429f28, tts_mcxt = 0x1429640, tts_buffer = 0, tts_nvalid = 1,
tts_values = 0x142a1a0, tts_isnull = 0x142a1b8, 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 = 4, tts_fixedTupleDescriptor = true}
(gdb) p values
$23 = {0, 7152626, 21144656, 21144128, 7141053, 21143088, 21144128, 16372128, 140722434628688, 0, 0, 0, 21143872,
140722434628736, 140461078524324, 21141056, 21144128, 0, 21143088, 21141056, 7152279, 0, 7421941, 21141056, 21143088,
21614576, 140722434628800, 7422189, 21143872, 140722434628839, 21143088, 21144128}
(gdb) p isnull
$24 = {false, 91, 186, 126, 252, 127, false, false, 208, 166, 71, false, false, false, false, false, 2,
false }
(gdb) p *estate
$25 = {type = T_EState, es_direction = ForwardScanDirection, es_snapshot = 0x1451ee0, es_crosscheck_snapshot = 0x0,
es_range_table = 0x14a71c0, es_plannedstmt = 0x14a72b8,
es_sourceText = 0x13acec8 "insert into t_hash_partition(c1,c2,c3) VALUES(0,'HASH0','HAHS0');", es_junkFilter = 0x0,
es_output_cid = 0, es_result_relations = 0x14299a8, es_num_result_relations = 1, es_result_relation_info = 0x14299a8,
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 = 0x142afc0, es_trig_oldtup_slot = 0x0, es_trig_newtup_slot = 0x0,
es_param_list_info = 0x0, es_param_exec_vals = 0x1429970, es_queryEnv = 0x0, es_query_cxt = 0x1429640,
es_tupleTable = 0x142a200, es_rowMarks = 0x0, es_processed = 0, es_lastoid = 0, es_top_eflags = 0, es_instrument = 0,
es_finished = false, es_exprcontexts = 0x1429ef0, es_subplanstates = 0x0, es_auxmodifytables = 0x0,
es_per_tuple_exprcontext = 0x142b080, 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, es_jit_worker_instr = 0x0}
(gdb)
进入get_partition_for_tuple函数
(gdb) n
288 cur_index = get_partition_for_tuple(rel, values, isnull);
(gdb) step
get_partition_for_tuple (relation=0x7fbfa6900950, values=0x7ffc7eba5bb0, isnull=0x7ffc7eba5b90) at execPartition.c:1139
1139 int part_index = -1;
(gdb)
get_partition_for_tuple->获取分区键
1139 int part_index = -1;
(gdb) n
1140 PartitionKey key = RelationGetPartitionKey(relation);
(gdb)
1141 PartitionDesc partdesc = RelationGetPartitionDesc(relation);
(gdb) p key
$26 = (PartitionKey) 0x1489860
(gdb) p *key
$27 = {strategy = 104 'h', partnatts = 1, partattrs = 0x14898f8, partexprs = 0x0, partopfamily = 0x1489918,
partopcintype = 0x1489938, partsupfunc = 0x1489958, partcollation = 0x14899b0, parttypid = 0x14899d0,
parttypmod = 0x14899f0, parttyplen = 0x1489a10, parttypbyval = 0x1489a30,
parttypalign = 0x1489a50 "i~\177\177\177\177\177\177\b", parttypcoll = 0x1489a70}
get_partition_for_tuple->获取分区描述符&分区边界信息
(gdb) n
1142 PartitionBoundInfo boundinfo = partdesc->boundinfo;
(gdb)
1145 switch (key->strategy)
(gdb) p *partdesc
$28 = {nparts = 6, oids = 0x149b168, boundinfo = 0x149b1a0}
(gdb) p *boundinfo
$29 = {strategy = 104 'h', ndatums = 6, datums = 0x149b1f8, kind = 0x0, indexes = 0x149b288, null_index = -1,
default_index = -1}
get_partition_for_tuple->进入Hash分区处理分支
(gdb) n
1152 greatest_modulus = get_hash_partition_greatest_modulus(boundinfo);
(gdb) p key->strategy
$30 = 104 'h'
get_partition_for_tuple->计算模块数&行hash值,获得分区编号(index)
(gdb) n
1153 rowHash = compute_partition_hash_value(key->partnatts,
(gdb) n
1157 part_index = boundinfo->indexes[rowHash % greatest_modulus];
(gdb)
1159 break;
(gdb) p part_index
$31 = 2
(gdb)
get_partition_for_tuple->返回
(gdb) n
1228 if (part_index < 0)
(gdb)
1231 return part_index;
(gdb)
1232 }
(gdb)
ExecFindPartition (resultRelInfo=0x14299a8, pd=0x142ae58, slot=0x142a140, estate=0x1429758) at execPartition.c:295
295 if (cur_index < 0)
(gdb)
已取得分区信息(分区索引编号=2)
(gdb) n
300 else if (dispatch->indexes[cur_index] >= 0)
(gdb)
302 result = dispatch->indexes[cur_index];
(gdb) p dispatch->indexes[cur_index]
$32 = 2
(gdb) n
304 break;
(gdb)
324 if (slot == myslot)
(gdb)
328 if (result < 0)
(gdb)
342 MemoryContextSwitchTo(oldcxt);
(gdb)
343 ecxt->ecxt_scantuple = ecxt_scantuple_old;
(gdb)
345 return result;
(gdb)
完成函数调用
(gdb) n
346 }
(gdb)
ExecPrepareTupleRouting (mtstate=0x1429ac0, estate=0x1429758, proute=0x142a7a8, targetRelInfo=0x14299a8, slot=0x142a140)
at nodeModifyTable.c:1716
1716 Assert(partidx >= 0 && partidx < proute->num_partitions);
DONE!
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.
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