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這篇文章將為大家詳細(xì)講解有關(guān)PostgreSQL中prune_append_rel_partitions->get_matching_partitions函數(shù)怎么用，小編覺(jué)得挺實(shí)用的，因此分享給大家做個(gè)參考，希望大家閱讀完這篇文章后可以有所收獲。
PartitionScheme
分區(qū)方案,根據(jù)設(shè)計(jì)，分區(qū)方案只包含分區(qū)方法的一般屬性(列表與范圍、分區(qū)列的數(shù)量和每個(gè)分區(qū)列的類型信息)，而不包含特定的分區(qū)邊界信息。
/*
* If multiple relations are partitioned the same way, all such partitions
* will have a pointer to the same PartitionScheme. A list of PartitionScheme
* objects is attached to the PlannerInfo. By design, the partition scheme
* incorporates only the general properties of the partition method (LIST vs.
* RANGE, number of partitioning columns and the type information for each)
* and not the specific bounds.
* 如果多個(gè)關(guān)系以相同的方式分區(qū)，那么所有這些分區(qū)都將具有指向相同PartitionScheme的指針。
* PartitionScheme對(duì)象的鏈表附加到PlannerInfo中。
* 根據(jù)設(shè)計(jì)，分區(qū)方案只包含分區(qū)方法的一般屬性(列表與范圍、分區(qū)列的數(shù)量和每個(gè)分區(qū)列的類型信息)，
* 而不包含特定的界限。
*
* We store the opclass-declared input data types instead of the partition key
* datatypes since the former rather than the latter are used to compare
* partition bounds. Since partition key data types and the opclass declared
* input data types are expected to be binary compatible (per ResolveOpClass),
* both of those should have same byval and length properties.
* 我們存儲(chǔ)opclass-declared的輸入數(shù)據(jù)類型，而不是分區(qū)鍵數(shù)據(jù)類型，
* 因?yàn)榍罢哂糜诒容^分區(qū)邊界，而不是后者。
* 由于分區(qū)鍵數(shù)據(jù)類型和opclass-declared的輸入數(shù)據(jù)類型預(yù)期是二進(jìn)制兼容的(每個(gè)ResolveOpClass)，
* 所以它們應(yīng)該具有相同的byval和length屬性。
*/
typedef struct PartitionSchemeData
{
char strategy; /* 分區(qū)策略;partition strategy */
int16 partnatts; /* 分區(qū)屬性個(gè)數(shù);number of partition attributes */
Oid *partopfamily; /* 操作符族OIDs;OIDs of operator families */
Oid *partopcintype; /* opclass聲明的輸入數(shù)據(jù)類型的OIDs;OIDs of opclass declared input data types */
Oid *partcollation; /* 分區(qū)排序規(guī)則OIDs;OIDs of partitioning collations */
/* Cached information about partition key data types. */
//緩存有關(guān)分區(qū)鍵數(shù)據(jù)類型的信息。
int16 *parttyplen;
bool *parttypbyval;
/* Cached information about partition comparison functions. */
//緩存有關(guān)分區(qū)比較函數(shù)的信息。
FmgrInfo *partsupfunc;
} PartitionSchemeData;
typedef struct PartitionSchemeData *PartitionScheme;PartitionPruneXXX
執(zhí)行Prune期間需要使用的數(shù)據(jù)結(jié)構(gòu),包括PartitionPruneStep/PartitionPruneStepOp/PartitionPruneCombineOp/PartitionPruneStepCombine
/*
* Abstract Node type for partition pruning steps (there are no concrete
* Nodes of this type).
* 用于分區(qū)修剪步驟pruning的抽象節(jié)點(diǎn)類型(沒(méi)有這種類型的具體節(jié)點(diǎn))。
*
* step_id is the global identifier of the step within its pruning context.
* step_id是步驟在其修剪pruning上下文中的全局標(biāo)識(shí)符。
*/
typedef struct PartitionPruneStep
{
NodeTag type;
int step_id;
} PartitionPruneStep;
/*
* PartitionPruneStepOp - Information to prune using a set of mutually AND'd
* OpExpr clauses
* PartitionPruneStepOp - 使用一組AND操作的OpExpr條件子句進(jìn)行修剪prune的信息
*
* This contains information extracted from up to partnatts OpExpr clauses,
* where partnatts is the number of partition key columns. 'opstrategy' is the
* strategy of the operator in the clause matched to the last partition key.
* 'exprs' contains expressions which comprise the lookup key to be passed to
* the partition bound search function. 'cmpfns' contains the OIDs of
* comparison functions used to compare aforementioned expressions with
* partition bounds. Both 'exprs' and 'cmpfns' contain the same number of
* items, up to partnatts items.
* 它包含從partnatts OpExpr子句中提取的信息，
* 其中partnatts是分區(qū)鍵列的數(shù)量。
* “opstrategy”是子句中與最后一個(gè)分區(qū)鍵匹配的操作符的策略。
* 'exprs'包含一些表達(dá)式，這些表達(dá)式包含要傳遞給分區(qū)綁定搜索函數(shù)的查找鍵。
* “cmpfns”包含用于比較上述表達(dá)式與分區(qū)邊界的比較函數(shù)的OIDs。
* “exprs”和“cmpfns”包含相同數(shù)量的條目，最多包含partnatts個(gè)條目。
*
* Once we find the offset of a partition bound using the lookup key, we
* determine which partitions to include in the result based on the value of
* 'opstrategy'. For example, if it were equality, we'd return just the
* partition that would contain that key or a set of partitions if the key
* didn't consist of all partitioning columns. For non-equality strategies,
* we'd need to include other partitions as appropriate.
* 一旦我們使用查找鍵找到分區(qū)綁定的偏移量，
* 我們將根據(jù)“opstrategy”的值確定在結(jié)果中包含哪些分區(qū)。
* 例如，如果它是相等的，我們只返回包含該鍵的分區(qū)，或者如果該鍵不包含所有分區(qū)列，
* 則返回一組分區(qū)。
* 對(duì)于非等值的情況，需要適當(dāng)?shù)匕ㄆ渌謪^(qū)。
*
* 'nullkeys' is the set containing the offset of the partition keys (0 to
* partnatts - 1) that were matched to an IS NULL clause. This is only
* considered for hash partitioning as we need to pass which keys are null
* to the hash partition bound search function. It is never possible to
* have an expression be present in 'exprs' for a given partition key and
* the corresponding bit set in 'nullkeys'.
* 'nullkeys'是包含與is NULL子句匹配的分區(qū)鍵(0到partnatts - 1)偏移量的集合。
* 這只適用于哈希分區(qū)，因?yàn)槲覀冃枰獙⒛男╂I為null傳遞給哈希分區(qū)綁定搜索函數(shù)。
* 對(duì)于給定的分區(qū)鍵和“nullkeys”中設(shè)置的相應(yīng)bit，不可能在“exprs”中出現(xiàn)表達(dá)式。
*/
typedef struct PartitionPruneStepOp
{
PartitionPruneStep step;
StrategyNumber opstrategy;
List *exprs;
List *cmpfns;
Bitmapset *nullkeys;
} PartitionPruneStepOp;
/*
* PartitionPruneStepCombine - Information to prune using a BoolExpr clause
* PartitionPruneStepCombine - 使用BoolExpr條件prune的信息
*
* For BoolExpr clauses, we combine the set of partitions determined for each
* of the argument clauses.
* 對(duì)于BoolExpr子句，我們?yōu)槊總€(gè)參數(shù)子句確定的分區(qū)集進(jìn)行組合。
*/
typedef enum PartitionPruneCombineOp
{
PARTPRUNE_COMBINE_UNION,
PARTPRUNE_COMBINE_INTERSECT
} PartitionPruneCombineOp;
typedef struct PartitionPruneStepCombine
{
PartitionPruneStep step;
PartitionPruneCombineOp combineOp;
List *source_stepids;
} PartitionPruneStepCombine;
/* The result of performing one PartitionPruneStep */
//執(zhí)行PartitionPruneStep步驟后的結(jié)果
typedef struct PruneStepResult
{
/*
* The offsets of bounds (in a table's boundinfo) whose partition is
* selected by the pruning step.
* 被pruning步驟選中的分區(qū)邊界(在數(shù)據(jù)表boundinfo中)偏移
*/
Bitmapset *bound_offsets;
bool scan_default; /* 是否掃描默認(rèn)分區(qū)? Scan the default partition? */
bool scan_null; /* 是否為NULL值掃描分區(qū)? Scan the partition for NULL values? */
} PruneStepResult;get_matching_partitions函數(shù)確定在分區(qū)pruning后仍然"存活"的分區(qū)。
/*
* get_matching_partitions
* Determine partitions that survive partition pruning
* 確定在分區(qū)修剪pruning后仍然存在的分區(qū).
*
* Returns a Bitmapset of the RelOptInfo->part_rels indexes of the surviving
* partitions.
* 返回pruning后仍存在的分區(qū)的RelOptInfo->part_rels索引位圖集。
*/
Bitmapset *
get_matching_partitions(PartitionPruneContext *context, List *pruning_steps)
{
Bitmapset *result;
int num_steps = list_length(pruning_steps),
i;
PruneStepResult **results,
*final_result;
ListCell *lc;
/* If there are no pruning steps then all partitions match. */
//沒(méi)有pruning步驟,則視為保留所有分區(qū)
if (num_steps == 0)
{
Assert(context->nparts > 0);
return bms_add_range(NULL, 0, context->nparts - 1);
}
/*
* Allocate space for individual pruning steps to store its result. Each
* slot will hold a PruneStepResult after performing a given pruning step.
* Later steps may use the result of one or more earlier steps. The
* result of applying all pruning steps is the value contained in the slot
* of the last pruning step.
* 為單個(gè)修剪步驟分配空間來(lái)存儲(chǔ)結(jié)果。
* 每個(gè)slot將持有pruning后，執(zhí)行一個(gè)給定的pruning步驟。
* 后面的步驟可以使用前面一個(gè)或多個(gè)步驟的結(jié)果。
* 應(yīng)用所有步驟的結(jié)果是最后一個(gè)步驟的slot中包含的值。
*/
results = (PruneStepResult **)
palloc0(num_steps * sizeof(PruneStepResult *));
foreach(lc, pruning_steps)//遍歷步驟
{
PartitionPruneStep *step = lfirst(lc);
switch (nodeTag(step))
{
case T_PartitionPruneStepOp:
results[step->step_id] =
perform_pruning_base_step(context,
(PartitionPruneStepOp *) step);//執(zhí)行pruning基礎(chǔ)步驟
break;
case T_PartitionPruneStepCombine:
results[step->step_id] =
perform_pruning_combine_step(context,
(PartitionPruneStepCombine *) step,
results);//執(zhí)行pruning組合步驟
break;
default:
elog(ERROR, "invalid pruning step type: %d",
(int) nodeTag(step));
}
}
/*
* At this point we know the offsets of all the datums whose corresponding
* partitions need to be in the result, including special null-accepting
* and default partitions. Collect the actual partition indexes now.
* 到目前為止,我們已經(jīng)知道結(jié)果中需要的相應(yīng)分區(qū)的所有數(shù)據(jù)的偏移量，
* 包括特殊的接受null的分區(qū)和默認(rèn)分區(qū)。
* 現(xiàn)在收集實(shí)際的分區(qū)索引。
*/
final_result = results[num_steps - 1];//最終結(jié)果
Assert(final_result != NULL);
i = -1;
result = NULL;
while ((i = bms_next_member(final_result->bound_offsets, i)) >= 0)
{
int partindex = context->boundinfo->indexes[i];//分區(qū)編號(hào)
/*
* In range and hash partitioning cases, some slots may contain -1,
* indicating that no partition has been defined to accept a given
* range of data or for a given remainder, respectively. The default
* partition, if any, in case of range partitioning, will be added to
* the result, because the specified range still satisfies the query's
* conditions.
* 范圍分區(qū)和散列分區(qū)，一些slot可能包含-1，
* 這表示沒(méi)有定義接受給定范圍的數(shù)據(jù)或給定余數(shù)的分區(qū)。
* 在范圍分區(qū)的情況下，默認(rèn)分區(qū)(如果有的話)將被添加到結(jié)果中，
* 因?yàn)橹付ǖ姆秶匀粷M足查詢的條件。
*/
if (partindex >= 0)
result = bms_add_member(result, partindex);
}
/* Add the null and/or default partition if needed and if present. */
//如果需要，添加NULL和/或默認(rèn)分區(qū)。
if (final_result->scan_null)
{
Assert(context->strategy == PARTITION_STRATEGY_LIST);
Assert(partition_bound_accepts_nulls(context->boundinfo));
result = bms_add_member(result, context->boundinfo->null_index);
}
if (final_result->scan_default)
{
Assert(context->strategy == PARTITION_STRATEGY_LIST ||
context->strategy == PARTITION_STRATEGY_RANGE);
Assert(partition_bound_has_default(context->boundinfo));
result = bms_add_member(result, context->boundinfo->default_index);
}
return result;
}
/*
* perform_pruning_base_step
* Determines the indexes of datums that satisfy conditions specified in
* 'opstep'.
* 確定滿足“opstep”中指定條件的數(shù)據(jù)索引。
*
* Result also contains whether special null-accepting and/or default
* partition need to be scanned.
* 結(jié)果還包含是否需要掃描特殊的可接受null和/或默認(rèn)分區(qū)。
*/
static PruneStepResult *
perform_pruning_base_step(PartitionPruneContext *context,
PartitionPruneStepOp *opstep)
{
ListCell *lc1,
*lc2;
int keyno,
nvalues;
Datum values[PARTITION_MAX_KEYS];
FmgrInfo *partsupfunc;
int stateidx;
/*
* There better be the same number of expressions and compare functions.
* 最好有相同數(shù)量的表達(dá)式和比較函數(shù)。
*/
Assert(list_length(opstep->exprs) == list_length(opstep->cmpfns));
nvalues = 0;
lc1 = list_head(opstep->exprs);
lc2 = list_head(opstep->cmpfns);
/*
* Generate the partition lookup key that will be used by one of the
* get_matching_*_bounds functions called below.
* 生成將由下面調(diào)用的get_matching_*_bounds函數(shù)使用的分區(qū)查找鍵。
*/
for (keyno = 0; keyno < context->partnatts; keyno++)
{
/*
* For hash partitioning, it is possible that values of some keys are
* not provided in operator clauses, but instead the planner found
* that they appeared in a IS NULL clause.
* 對(duì)于哈希分區(qū)，操作符子句中可能沒(méi)有提供某些鍵的值，
* 但是計(jì)劃器發(fā)現(xiàn)它們出現(xiàn)在is NULL子句中。
*/
if (bms_is_member(keyno, opstep->nullkeys))
continue;
/*
* For range partitioning, we must only perform pruning with values
* for either all partition keys or a prefix thereof.
* 對(duì)于范圍分區(qū)，我們必須只對(duì)所有分區(qū)鍵或其前綴執(zhí)行值修剪pruning。
*/
if (keyno > nvalues && context->strategy == PARTITION_STRATEGY_RANGE)
break;
if (lc1 != NULL)//步驟的條件表達(dá)式不為NULL
{
Expr *expr;
Datum datum;
bool isnull;
expr = lfirst(lc1);
stateidx = PruneCxtStateIdx(context->partnatts,
opstep->step.step_id, keyno);
if (partkey_datum_from_expr(context, expr, stateidx,
&datum, &isnull))
{
Oid cmpfn;
/*
* Since we only allow strict operators in pruning steps, any
* null-valued comparison value must cause the comparison to
* fail, so that no partitions could match.
* 由于我們只允許在修剪pruning步驟中使用嚴(yán)格的操作符，
* 任何空值比較值都必須導(dǎo)致比較失敗，這樣就沒(méi)有分區(qū)能夠匹配。
*/
if (isnull)
{
PruneStepResult *result;
result = (PruneStepResult *) palloc(sizeof(PruneStepResult));
result->bound_offsets = NULL;
result->scan_default = false;
result->scan_null = false;
return result;
}
/* Set up the stepcmpfuncs entry, unless we already did */
//配置stepcmpfuncs(步驟比較函數(shù))入口
cmpfn = lfirst_oid(lc2);
Assert(OidIsValid(cmpfn));
if (cmpfn != context->stepcmpfuncs[stateidx].fn_oid)
{
/*
* If the needed support function is the same one cached
* in the relation's partition key, copy the cached
* FmgrInfo. Otherwise (i.e., when we have a cross-type
* comparison), an actual lookup is required.
* 如果所需的支持函數(shù)與關(guān)系分區(qū)鍵緩存的支持函數(shù)相同，
* 則復(fù)制緩存的FmgrInfo。
* 否則(比如存在一個(gè)跨類型比較時(shí))，需要實(shí)際的查找。
*/
if (cmpfn == context->partsupfunc[keyno].fn_oid)
fmgr_info_copy(&context->stepcmpfuncs[stateidx],
&context->partsupfunc[keyno],
context->ppccontext);
else
fmgr_info_cxt(cmpfn, &context->stepcmpfuncs[stateidx],
context->ppccontext);
}
values[keyno] = datum;
nvalues++;
}
lc1 = lnext(lc1);
lc2 = lnext(lc2);
}
}
/*
* Point partsupfunc to the entry for the 0th key of this step; the
* additional support functions, if any, follow consecutively.
* 將partsupfunc指向此步驟第0個(gè)鍵的條目;
* 附加的支持功能(如果有的話)是連續(xù)的。
*/
stateidx = PruneCxtStateIdx(context->partnatts, opstep->step.step_id, 0);
partsupfunc = &context->stepcmpfuncs[stateidx];
switch (context->strategy)
{
case PARTITION_STRATEGY_HASH:
return get_matching_hash_bounds(context,
opstep->opstrategy,
values, nvalues,
partsupfunc,
opstep->nullkeys);
case PARTITION_STRATEGY_LIST:
return get_matching_list_bounds(context,
opstep->opstrategy,
values[0], nvalues,
&partsupfunc[0],
opstep->nullkeys);
case PARTITION_STRATEGY_RANGE:
return get_matching_range_bounds(context,
opstep->opstrategy,
values, nvalues,
partsupfunc,
opstep->nullkeys);
default:
elog(ERROR, "unexpected partition strategy: %d",
(int) context->strategy);
break;
}
return NULL;
}
/*
* perform_pruning_combine_step
* Determines the indexes of datums obtained by combining those given
* by the steps identified by cstep->source_stepids using the specified
* combination method
* 使用指定的組合方法將cstep->source_stepids標(biāo)識(shí)的步驟組合在一起得到數(shù)據(jù)索引
*
* Since cstep may refer to the result of earlier steps, we also receive
* step_results here.
* 因?yàn)閏step可能引用前面步驟的結(jié)果，所以在這里也會(huì)收到step_results。
*/
static PruneStepResult *
perform_pruning_combine_step(PartitionPruneContext *context,
PartitionPruneStepCombine *cstep,
PruneStepResult **step_results)
{
ListCell *lc1;
PruneStepResult *result = NULL;
bool firststep;
/*
* A combine step without any source steps is an indication to not perform
* any partition pruning, we just return all partitions.
* 如無(wú)源步驟,則不執(zhí)行分區(qū)pruning,返回所有分區(qū)
*/
result = (PruneStepResult *) palloc0(sizeof(PruneStepResult));
if (list_length(cstep->source_stepids) == 0)
{
PartitionBoundInfo boundinfo = context->boundinfo;
result->bound_offsets = bms_add_range(NULL, 0, boundinfo->ndatums - 1);
result->scan_default = partition_bound_has_default(boundinfo);
result->scan_null = partition_bound_accepts_nulls(boundinfo);
return result;
}
switch (cstep->combineOp)//根據(jù)組合操作類型確定相應(yīng)邏輯
{
case PARTPRUNE_COMBINE_UNION://PARTPRUNE_COMBINE_UNION
foreach(lc1, cstep->source_stepids)
{
int step_id = lfirst_int(lc1);
PruneStepResult *step_result;
/*
* step_results[step_id] must contain a valid result, which is
* confirmed by the fact that cstep's step_id is greater than
* step_id and the fact that results of the individual steps
* are evaluated in sequence of their step_ids.
* step_results[step_id]必須包含一個(gè)有效的結(jié)果，
* cstep的step_id大于step_id，并且各個(gè)步驟的結(jié)果按其step_id的順序計(jì)算，
* 這一點(diǎn)是可以確認(rèn)的。
*/
if (step_id >= cstep->step.step_id)
elog(ERROR, "invalid pruning combine step argument");
step_result = step_results[step_id];
Assert(step_result != NULL);
/* Record any additional datum indexes from this step */
//記錄從該步驟產(chǎn)生的偏移索引
result->bound_offsets = bms_add_members(result->bound_offsets,
step_result->bound_offsets);
/* Update whether to scan null and default partitions. */
//更新掃描null/default分區(qū)的標(biāo)記
if (!result->scan_null)
result->scan_null = step_result->scan_null;
if (!result->scan_default)
result->scan_default = step_result->scan_default;
}
break;
case PARTPRUNE_COMBINE_INTERSECT://PARTPRUNE_COMBINE_INTERSECT
firststep = true;
foreach(lc1, cstep->source_stepids)
{
int step_id = lfirst_int(lc1);
PruneStepResult *step_result;
if (step_id >= cstep->step.step_id)
elog(ERROR, "invalid pruning combine step argument");
step_result = step_results[step_id];
Assert(step_result != NULL);
if (firststep)//第一個(gè)步驟
{
/* Copy step's result the first time. */
//第一次,拷貝步驟的結(jié)果
result->bound_offsets =
bms_copy(step_result->bound_offsets);
result->scan_null = step_result->scan_null;
result->scan_default = step_result->scan_default;
firststep = false;
}
else
{
/* Record datum indexes common to both steps */
//記錄其他步驟產(chǎn)生的索引
result->bound_offsets =
bms_int_members(result->bound_offsets,
step_result->bound_offsets);
/* Update whether to scan null and default partitions. */
//更新掃描null/default分區(qū)的標(biāo)記
if (result->scan_null)
result->scan_null = step_result->scan_null;
if (result->scan_default)
result->scan_default = step_result->scan_default;
}
}
break;
}
return result;
}
/*
* get_matching_hash_bounds
* Determine offset of the hash bound matching the specified values,
* considering that all the non-null values come from clauses containing
* a compatible hash equality operator and any keys that are null come
* from an IS NULL clause.
* 考慮到所有非空值都來(lái)自包含兼容的哈希相等操作符的子句，
* 而所有空鍵都來(lái)自IS NULL子句，因此確定匹配指定值的哈希邊界的偏移量。
*
* Generally this function will return a single matching bound offset,
* although if a partition has not been setup for a given modulus then we may
* return no matches. If the number of clauses found don't cover the entire
* partition key, then we'll need to return all offsets.
* 通常，這個(gè)函數(shù)會(huì)返回一個(gè)匹配的邊界偏移量，
* 但是如果沒(méi)有為給定的模數(shù)設(shè)置分區(qū)，則可能不返回匹配值。
* 如果找到的子句數(shù)量不包含整個(gè)分區(qū)鍵，那么我們需要返回所有偏移量。
*
* 'opstrategy' if non-zero must be HTEqualStrategyNumber.
* opstrategy - 如非0,則為HTEqualStrategyNumber
*
* 'values' contains Datums indexed by the partition key to use for pruning.
* values 包含用于分區(qū)鍵執(zhí)行pruning的數(shù)據(jù)值
*
* 'nvalues', the number of Datums in the 'values' array.
* nvalues values數(shù)組大小
*
* 'partsupfunc' contains partition hashing functions that can produce correct
* hash for the type of the values contained in 'values'.
* partsupfunc 存儲(chǔ)分區(qū)hash函數(shù),可以為values產(chǎn)生hash值
*
* 'nullkeys' is the set of partition keys that are null.
* nullkeys 為null的分區(qū)鍵值集合
*/
static PruneStepResult *
get_matching_hash_bounds(PartitionPruneContext *context,
StrategyNumber opstrategy, Datum *values, int nvalues,
FmgrInfo *partsupfunc, Bitmapset *nullkeys)
{
PruneStepResult *result = (PruneStepResult *) palloc0(sizeof(PruneStepResult));
PartitionBoundInfo boundinfo = context->boundinfo;
int *partindices = boundinfo->indexes;
int partnatts = context->partnatts;
bool isnull[PARTITION_MAX_KEYS];
int i;
uint64 rowHash;
int greatest_modulus;
Assert(context->strategy == PARTITION_STRATEGY_HASH);
/*
* For hash partitioning we can only perform pruning based on equality
* clauses to the partition key or IS NULL clauses. We also can only
* prune if we got values for all keys.
* 對(duì)于Hash分區(qū),只能基于等值條件語(yǔ)句或者是IS NULL條件進(jìn)行pruning.
* 當(dāng)然,如果可以拿到所有鍵的值,也可以執(zhí)行prune
*/
if (nvalues + bms_num_members(nullkeys) == partnatts)
{
/*
* If there are any values, they must have come from clauses
* containing an equality operator compatible with hash partitioning.
* 如存在values,那么這些值必須從包含一個(gè)與hash分區(qū)兼容的等值操作符的條件語(yǔ)句而來(lái)
*/
Assert(opstrategy == HTEqualStrategyNumber || nvalues == 0);
for (i = 0; i < partnatts; i++)
isnull[i] = bms_is_member(i, nullkeys);
greatest_modulus = get_hash_partition_greatest_modulus(boundinfo);
rowHash = compute_partition_hash_value(partnatts, partsupfunc,
values, isnull);
if (partindices[rowHash % greatest_modulus] >= 0)
result->bound_offsets =
bms_make_singleton(rowHash % greatest_modulus);
}
else
{
/* Getting here means at least one hash partition exists. */
//程序執(zhí)行到這里,意味著至少存在一個(gè)hash分區(qū)
Assert(boundinfo->ndatums > 0);
result->bound_offsets = bms_add_range(NULL, 0,
boundinfo->ndatums - 1);
}
/*
* There is neither a special hash null partition or the default hash
* partition.
* 要么存在一個(gè)特別的hash null分區(qū),要么是默認(rèn)的hash分區(qū)
*/
result->scan_null = result->scan_default = false;
return result;
}測(cè)試腳本如下
testdb=# explain verbose select * from t_hash_partition where c1 = 1 OR c1 = 2; QUERY PLAN ------------------------------------------------------------------------------------- Append (cost=0.00..30.53 rows=6 width=200) -> Seq Scan on public.t_hash_partition_1 (cost=0.00..15.25 rows=3 width=200) Output: t_hash_partition_1.c1, t_hash_partition_1.c2, t_hash_partition_1.c3 Filter: ((t_hash_partition_1.c1 = 1) OR (t_hash_partition_1.c1 = 2)) -> Seq Scan on public.t_hash_partition_3 (cost=0.00..15.25 rows=3 width=200) Output: t_hash_partition_3.c1, t_hash_partition_3.c2, t_hash_partition_3.c3 Filter: ((t_hash_partition_3.c1 = 1) OR (t_hash_partition_3.c1 = 2)) (7 rows)
啟動(dòng)gdb,設(shè)置斷點(diǎn)
(gdb) b get_matching_partitions Breakpoint 1 at 0x804d3b: file partprune.c, line 619. (gdb) c Continuing. Breakpoint 1, get_matching_partitions (context=0x7fff4a5e3930, pruning_steps=0x14d5300) at partprune.c:619 619 int num_steps = list_length(pruning_steps), (gdb) n 626 if (num_steps == 0)
查看輸入?yún)?shù),pruning_steps是有3個(gè)ITEM的鏈表
(gdb) p *pruning_steps
$1 = {type = T_List, length = 3, head = 0x14d52d8, tail = 0x14d58d0}pruning_steps的3個(gè)ITEM類型分別是PartitionPruneStepOp/PartitionPruneStepOp/PartitionPruneStepCombine
第1和2個(gè)ITEM的expr是Const,即常量1和2
(gdb) p *(Node *)pruning_steps->head->data.ptr_value
$2 = {type = T_PartitionPruneStepOp} -->Node類型
(gdb) p *(PartitionPruneStepOp *)pruning_steps->head->data.ptr_value
$3 = {step = {type = T_PartitionPruneStepOp, step_id = 0}, opstrategy = 1, exprs = 0x14d52a0, cmpfns = 0x14d5240,
nullkeys = 0x0}
(gdb) set $ppso=(PartitionPruneStepOp *)pruning_steps->head->data.ptr_value
(gdb) p *$ppso->exprs
$4 = {type = T_List, length = 1, head = 0x14d5278, tail = 0x14d5278}
(gdb) p *(Node *)$ppso->exprs->head->data.ptr_value
$5 = {type = T_Const}
(gdb) p *(Const *)$ppso->exprs->head->data.ptr_value
$6 = {xpr = {type = T_Const}, consttype = 23, consttypmod = -1, constcollid = 0, constlen = 4, constvalue = 1,
constisnull = false, constbyval = true, location = 42} -->第1個(gè)步驟的表達(dá)式,常量1
(gdb) set $ppso=(PartitionPruneStepOp *)pruning_steps->head->next->data.ptr_value
(gdb) p *(Const *)$ppso->exprs->head->data.ptr_value
$7 = {xpr = {type = T_Const}, consttype = 23, consttypmod = -1, constcollid = 0, constlen = 4, constvalue = 2,
constisnull = false, constbyval = true, location = 52} -->第2個(gè)步驟的表達(dá)式,常量2
(gdb) p *(Node *)pruning_steps->head->next->next->data.ptr_value
$8 = {type = T_PartitionPruneStepCombine}
(gdb) set $ppsc=(PartitionPruneStepCombine *)pruning_steps->head->next->next->data.ptr_value
(gdb) p *$ppsc
$9 = {step = {type = T_PartitionPruneStepCombine, step_id = 2}, combineOp = PARTPRUNE_COMBINE_UNION,
source_stepids = 0x14d5480} -->第3個(gè)步驟,組合操作是PARTPRUNE_COMBINE_UNION為步驟結(jié)果分配內(nèi)存
(gdb) n 640 palloc0(num_steps * sizeof(PruneStepResult *)); (gdb) p num_steps $10 = 3 (gdb) n 639 results = (PruneStepResult **) (gdb) 641 foreach(lc, pruning_steps)
開(kāi)始遍歷pruning步驟,進(jìn)入perform_pruning_base_step函數(shù)
(gdb) 643 PartitionPruneStep *step = lfirst(lc); (gdb) 645 switch (nodeTag(step)) (gdb) 648 results[step->step_id] = (gdb) step 649 perform_pruning_base_step(context, (gdb) perform_pruning_base_step (context=0x7fff4a5e3930, opstep=0x14d4e98) at partprune.c:2995 2995 Assert(list_length(opstep->exprs) == list_length(opstep->cmpfns));
perform_pruning_base_step->查看輸入?yún)?shù),比較函數(shù)是OID=425的函數(shù)
(gdb) p *opstep->cmpfns
$12 = {type = T_OidList, length = 1, head = 0x14d5218, tail = 0x14d5218}
(gdb) p opstep->cmpfns->head->data.oid_value
$16 = 425
(gdb) n
2998 lc1 = list_head(opstep->exprs);
(gdb)
2999 lc2 = list_head(opstep->cmpfns);
(gdb)perform_pruning_base_step->遍歷分區(qū)鍵
(gdb)
3005 for (keyno = 0; keyno < context->partnatts; keyno++)
(gdb)
3012 if (bms_is_member(keyno, opstep->nullkeys)) -->沒(méi)有null鍵
(gdb)
3019 if (keyno > nvalues && context->strategy == PARTITION_STRATEGY_RANGE) -->nvalues為0
(gdb) p nvalues
$17 = 0
(gdb) n
3022 if (lc1 != NULL)
(gdb)
3028 expr = lfirst(lc1); -->獲取步驟中的表達(dá)式,其實(shí)是常量1
(gdb)
3029 stateidx = PruneCxtStateIdx(context->partnatts, -->stateidx為0
(gdb) p *expr
$18 = {type = T_Const}
(gdb) p *(Const *)expr
$19 = {xpr = {type = T_Const}, consttype = 23, consttypmod = -1, constcollid = 0, constlen = 4, constvalue = 1,
constisnull = false, constbyval = true, location = 42}
(gdb) n
3031 if (partkey_datum_from_expr(context, expr, stateidx,
(gdb) p stateidx
$20 = 0
(gdb) n
3041 if (isnull) -->非NULL
(gdb) p isnull
$21 = falseperform_pruning_base_step->獲取比較函數(shù)進(jìn)行處理
(gdb) n 3054 cmpfn = lfirst_oid(lc2); --> OID=425 (gdb) 3055 Assert(OidIsValid(cmpfn)); (gdb) 3056 if (cmpfn != context->stepcmpfuncs[stateidx].fn_oid) -->fn_oid為0 (gdb) 3064 if (cmpfn == context->partsupfunc[keyno].fn_oid) -->fn_oid為425 (gdb) p context->stepcmpfuncs[stateidx].fn_oid $22 = 0 (gdb) p context->partsupfunc[keyno].fn_oid $23 = 425 (gdb) n 3065 fmgr_info_copy(&context->stepcmpfuncs[stateidx], (gdb) 3066 &context->partsupfunc[keyno], (gdb) 3065 fmgr_info_copy(&context->stepcmpfuncs[stateidx], (gdb) 3066 &context->partsupfunc[keyno], (gdb) 3065 fmgr_info_copy(&context->stepcmpfuncs[stateidx], --> 拷貝函數(shù) (gdb) 3073 values[keyno] = datum;-->設(shè)置值 (gdb) p datum $24 = 1 (gdb) n 3074 nvalues++; (gdb) 3077 lc1 = lnext(lc1); (gdb) 3078 lc2 = lnext(lc2); (gdb)
perform_pruning_base_step->完成分區(qū)鍵遍歷
(gdb) n 3005 for (keyno = 0; keyno < context->partnatts; keyno++) (gdb) 3086 stateidx = PruneCxtStateIdx(context->partnatts, opstep->step.step_id, 0); (gdb) 3087 partsupfunc = &context->stepcmpfuncs[stateidx]; (gdb) 3089 switch (context->strategy) (gdb) 3092 return get_matching_hash_bounds(context, (gdb)
perform_pruning_base_step->進(jìn)入get_matching_hash_bounds函數(shù)
(gdb) 3092 return get_matching_hash_bounds(context, (gdb) step 3093 opstep->opstrategy, (gdb) 3092 return get_matching_hash_bounds(context, (gdb) get_matching_hash_bounds (context=0x7fff4a5e3930, opstrategy=1, values=0x7fff4a5e3750, nvalues=1, partsupfunc=0x14d3068, nullkeys=0x0) at partprune.c:2156 2156 PruneStepResult *result = (PruneStepResult *) palloc0(sizeof(PruneStepResult)); (gdb)
get_matching_hash_bounds->變量賦值
(gdb) n 2157 PartitionBoundInfo boundinfo = context->boundinfo; (gdb) 2158 int *partindices = boundinfo->indexes; (gdb) 2159 int partnatts = context->partnatts; (gdb) 2165 Assert(context->strategy == PARTITION_STRATEGY_HASH); (gdb) 2172 if (nvalues + bms_num_members(nullkeys) == partnatts) (gdb)
get_matching_hash_bounds->分區(qū)邊界信息,共有6個(gè)分區(qū),Index分別是0-5
(gdb) p boundinfo
$25 = (PartitionBoundInfo) 0x14d32a0
(gdb) p *boundinfo
$26 = {strategy = 104 'h', ndatums = 6, datums = 0x14d32f8, kind = 0x0, indexes = 0x14d2e00, null_index = -1,
default_index = -1}
(gdb) p *boundinfo->datums
$27 = (Datum *) 0x14d3350
(gdb) p **boundinfo->datums
$28 = 6
(gdb) p **boundinfo->indexes
Cannot access memory at address 0x0
(gdb) p *boundinfo->indexes
$29 = 0
(gdb) p boundinfo->indexes[0]
$30 = 0
(gdb) p boundinfo->indexes[1]
$31 = 1
(gdb) p boundinfo->indexes[5]
$32 = 5
(gdb)get_matching_hash_bounds->分區(qū)索引和分區(qū)鍵數(shù)
(gdb) p *partindices $33 = 0 (gdb) p partnatts $34 = 1 (gdb) (gdb) p nvalues $35 = 1 (gdb) p bms_num_members(nullkeys) $36 = 0
get_matching_hash_bounds->遍歷分區(qū)鍵,判斷值是否落在分區(qū)中
(gdb) n 2178 Assert(opstrategy == HTEqualStrategyNumber || nvalues == 0); (gdb) 2180 for (i = 0; i < partnatts; i++) (gdb) 2181 isnull[i] = bms_is_member(i, nullkeys); (gdb) 2180 for (i = 0; i < partnatts; i++) (gdb) 2183 greatest_modulus = get_hash_partition_greatest_modulus(boundinfo); (gdb) 2184 rowHash = compute_partition_hash_value(partnatts, partsupfunc, (gdb) 2187 if (partindices[rowHash % greatest_modulus] >= 0)
get_matching_hash_bounds->
(gdb) p values $43 = (Datum *) 0x7fff4a5e3750 (gdb) p *values $44 = 1 --> 約束條件 (gdb) p isnull[0] $38 = false -->不為NULL (gdb) p greatest_modulus $39 = 6 -->6個(gè)分區(qū) (gdb) p rowHash $40 = 11274504255086170040 -->values算出的Hash值 (gdb) p rowHash % greatest_modulus $41 = 2 --> 所在的分區(qū) (gdb) p partindices[2] $42 = 2 -->存在該分區(qū) (gdb)
get_matching_hash_bounds->返回結(jié)果(bound_offsets->words=4,即編號(hào)2)
(gdb) n
2189 bms_make_singleton(rowHash % greatest_modulus);
(gdb)
2188 result->bound_offsets =
(gdb)
2203 result->scan_null = result->scan_default = false;
(gdb)
2205 return result;
(gdb)
2206 }
(gdb) p *result
$45 = {bound_offsets = 0x14d59b8, scan_default = false, scan_null = false}
(gdb) p *result->bound_offsets
$46 = {nwords = 1, words = 0x14d59bc}
(gdb) p *result->bound_offsets->words
$47 = 4
(gdb)回到get_matching_partitions
(gdb) n perform_pruning_base_step (context=0x7fff4a5e3930, opstep=0x14d4e98) at partprune.c:3119 3119 } (gdb) get_matching_partitions (context=0x7fff4a5e3930, pruning_steps=0x14d5300) at partprune.c:648 648 results[step->step_id] = (gdb) 651 break; (gdb) 641 foreach(lc, pruning_steps) (gdb) 643 PartitionPruneStep *step = lfirst(lc); (gdb) 645 switch (nodeTag(step)) (gdb) p
繼續(xù)執(zhí)行步驟,進(jìn)入perform_pruning_combine_step
654 results[step->step_id] = (gdb) 655 perform_pruning_combine_step(context, (gdb) step perform_pruning_combine_step (context=0x7fff4a5e3930, cstep=0x14d5898, step_results=0x14d5958) at partprune.c:3136 3136 PruneStepResult *result = NULL; (gdb)
perform_pruning_combine_step->進(jìn)入PARTPRUNE_COMBINE_UNION處理邏輯
(gdb) n
3143 result = (PruneStepResult *) palloc0(sizeof(PruneStepResult));
(gdb)
3144 if (list_length(cstep->source_stepids) == 0)
(gdb)
3154 switch (cstep->combineOp)
(gdb)
3157 foreach(lc1, cstep->source_stepids)
(gdb)
(gdb) p *cstep
$49 = {step = {type = T_PartitionPruneStepCombine, step_id = 2}, combineOp = PARTPRUNE_COMBINE_UNION,
source_stepids = 0x14d5480}perform_pruning_combine_step->遍歷組合步驟的源步驟 cstep->source_stepids,合并這些步驟的結(jié)果
(gdb) n 3159 int step_id = lfirst_int(lc1); ... (gdb) 3174 result->bound_offsets = bms_add_members(result->bound_offsets, (gdb) 3178 if (!result->scan_null) (gdb) 3179 result->scan_null = step_result->scan_null; (gdb) 3180 if (!result->scan_default) (gdb) 3181 result->scan_default = step_result->scan_default; (gdb) 3157 foreach(lc1, cstep->source_stepids) (gdb) 3183 break; (gdb) 3223 return result; (gdb)
perform_pruning_combine_step->最終結(jié)果
(gdb) p *result
$54 = {bound_offsets = 0x14d5a48, scan_default = false, scan_null = false}
(gdb) p *result->bound_offsets
$55 = {nwords = 1, words = 0x14d5a4c}
(gdb) p *result->bound_offsets->words
$56 = 5perform_pruning_combine_step->回到get_matching_partitions
(gdb) n 3224 } (gdb) get_matching_partitions (context=0x7fff4a5e3930, pruning_steps=0x14d5300) at partprune.c:654 654 results[step->step_id] =
完成所有步驟的處理
(gdb) n 658 break; (gdb) 641 foreach(lc, pruning_steps) (gdb) n 671 final_result = results[num_steps - 1]; (gdb) 672 Assert(final_result != NULL); (gdb)
構(gòu)造結(jié)果位圖集
... 675 while ((i = bms_next_member(final_result->bound_offsets, i)) >= 0) (gdb) n 677 int partindex = context->boundinfo->indexes[i]; (gdb) 687 if (partindex >= 0) (gdb) 688 result = bms_add_member(result, partindex); (gdb)
完成調(diào)用
gdb) 675 while ((i = bms_next_member(final_result->bound_offsets, i)) >= 0) (gdb) 692 if (final_result->scan_null) (gdb) 698 if (final_result->scan_default) (gdb) 706 return result; (gdb) 707 } (gdb)
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