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Fix an asssortment of typos in brin_minmax_multi.c and mcv.c

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Discussion: https://postgr.es/m/CAApHDvrbyJNOPBws4RUhXghZ7+TBjtdO-rznTsqZECuowNorXg@mail.gmail.com
This commit is contained in:
David Rowley
2021-06-10 20:13:44 +12:00
parent caba8f0d43
commit 55ba5973d9
2 changed files with 123 additions and 119 deletions
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81
src/backend/statistics/mcv.c
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@@ -212,10 +212,10 @@ statext_mcv_build(StatsBuildData *data, double totalrows, int stattarget)
groups = build_distinct_groups(nitems, items, mss, &ngroups);
/*
* Maximum number of MCV items to store, based on the statistics target we
* computed for the statistics object (from target set for the object
* itself, attributes and the system default). In any case, we can't keep
* more groups than we have available.
* The maximum number of MCV items to store, based on the statistics
* target we computed for the statistics object (from the target set for
* the object itself, attributes and the system default). In any case, we
* can't keep more groups than we have available.
*/
nitems = stattarget;
if (nitems > ngroups)
@@ -234,7 +234,7 @@ statext_mcv_build(StatsBuildData *data, double totalrows, int stattarget)
* to consider unexpectedly uncommon items (again, compared to the base
* frequency), and the single-column algorithm does not have to.
*
* We simply decide how many items to keep by computing minimum count
* We simply decide how many items to keep by computing the minimum count
* using get_mincount_for_mcv_list() and then keep all items that seem to
* be more common than that.
*/
@@ -255,9 +255,9 @@ statext_mcv_build(StatsBuildData *data, double totalrows, int stattarget)
}
/*
* At this point we know the number of items for the MCV list. There might
* be none (for uniform distribution with many groups), and in that case
* there will be no MCV list. Otherwise construct the MCV list.
* At this point, we know the number of items for the MCV list. There
* might be none (for uniform distribution with many groups), and in that
* case, there will be no MCV list. Otherwise, construct the MCV list.
*/
if (nitems > 0)
{
@@ -345,7 +345,7 @@ statext_mcv_build(StatsBuildData *data, double totalrows, int stattarget)
/*
* build_mss
* build MultiSortSupport for the attributes passed in attrs
* Build a MultiSortSupport for the given StatsBuildData.
*/
static MultiSortSupport
build_mss(StatsBuildData *data)
@@ -375,7 +375,7 @@ build_mss(StatsBuildData *data)
/*
* count_distinct_groups
* count distinct combinations of SortItems in the array
* Count distinct combinations of SortItems in the array.
*
* The array is assumed to be sorted according to the MultiSortSupport.
*/
@@ -400,7 +400,8 @@ count_distinct_groups(int numrows, SortItem *items, MultiSortSupport mss)
/*
* compare_sort_item_count
* comparator for sorting items by count (frequencies) in descending order
* Comparator for sorting items by count (frequencies) in descending
* order.
*/
static int
compare_sort_item_count(const void *a, const void *b)
@@ -418,9 +419,10 @@ compare_sort_item_count(const void *a, const void *b)
/*
* build_distinct_groups
* build an array of SortItems for distinct groups and counts matching items
* Build an array of SortItems for distinct groups and counts matching
* items.
*
* The input array is assumed to be sorted
* The 'items' array is assumed to be sorted.
*/
static SortItem *
build_distinct_groups(int numrows, SortItem *items, MultiSortSupport mss,
@@ -477,7 +479,7 @@ sort_item_compare(const void *a, const void *b, void *arg)
/*
* build_column_frequencies
* compute frequencies of values in each column
* Compute frequencies of values in each column.
*
* This returns an array of SortItems for each attribute the MCV is built
* on, with a frequency (number of occurrences) for each value. This is
@@ -554,7 +556,7 @@ build_column_frequencies(SortItem *groups, int ngroups,
/*
* statext_mcv_load
* Load the MCV list for the indicated pg_statistic_ext tuple
* Load the MCV list for the indicated pg_statistic_ext tuple.
*/
MCVList *
statext_mcv_load(Oid mvoid)
@@ -598,10 +600,11 @@ statext_mcv_load(Oid mvoid)
* | header fields | dimension info | deduplicated values | items |
* +---------------+----------------+---------------------+-------+
*
* Where dimension info stores information about type of K-th attribute (e.g.
* typlen, typbyval and length of deduplicated values). Deduplicated values
* store deduplicated values for each attribute. And items store the actual
* MCV list items, with values replaced by indexes into the arrays.
* Where dimension info stores information about the type of the K-th
* attribute (e.g. typlen, typbyval and length of deduplicated values).
* Deduplicated values store deduplicated values for each attribute. And
* items store the actual MCV list items, with values replaced by indexes into
* the arrays.
*
* When serializing the items, we use uint16 indexes. The number of MCV items
* is limited by the statistics target (which is capped to 10k at the moment).
@@ -641,10 +644,10 @@ statext_mcv_serialize(MCVList *mcvlist, VacAttrStats **stats)
/*
* We'll include some rudimentary information about the attribute types
* (length, by-val flag), so that we don't have to look them up while
* deserializating the MCV list (we already have the type OID in the
* header). This is safe, because when changing type of the attribute the
* statistics gets dropped automatically. We need to store the info about
* the arrays of deduplicated values anyway.
* deserializing the MCV list (we already have the type OID in the
* header). This is safe because when changing the type of the attribute
* the statistics gets dropped automatically. We need to store the info
* about the arrays of deduplicated values anyway.
*/
info = (DimensionInfo *) palloc0(sizeof(DimensionInfo) * ndims);
@@ -697,8 +700,8 @@ statext_mcv_serialize(MCVList *mcvlist, VacAttrStats **stats)
/*
* Walk through the array and eliminate duplicate values, but keep the
* ordering (so that we can do bsearch later). We know there's at
* least one item as (counts[dim] != 0), so we can skip the first
* ordering (so that we can do a binary search later). We know there's
* at least one item as (counts[dim] != 0), so we can skip the first
* element.
*/
ndistinct = 1; /* number of distinct values */
@@ -787,10 +790,10 @@ statext_mcv_serialize(MCVList *mcvlist, VacAttrStats **stats)
Size len;
/*
* For cstring, we do similar thing as for varlena - first we
* store the length as uint32 and then the data. We don't care
* about alignment, which means that during deserialization we
* need to copy the fields and only access the copies.
* cstring is handled similar to varlena - first we store the
* length as uint32 and then the data. We don't care about
* alignment, which means that during deserialization we need
* to copy the fields and only access the copies.
*/
/* c-strings include terminator, so +1 byte */
@@ -874,13 +877,13 @@ statext_mcv_serialize(MCVList *mcvlist, VacAttrStats **stats)
Datum tmp;
/*
* For values passed by value, we need to copy just the
* significant bytes - we can't use memcpy directly, as that
* assumes little endian behavior. store_att_byval does
* almost what we need, but it requires properly aligned
* buffer - the output buffer does not guarantee that. So we
* simply use a local Datum variable (which guarantees proper
* alignment), and then copy the value from it.
* For byval types, we need to copy just the significant bytes
* - we can't use memcpy directly, as that assumes
* little-endian behavior. store_att_byval does almost what
* we need, but it requires a properly aligned buffer - the
* output buffer does not guarantee that. So we simply use a
* local Datum variable (which guarantees proper alignment),
* and then copy the value from it.
*/
store_att_byval(&tmp, value, info[dim].typlen);
@@ -1698,7 +1701,7 @@ mcv_get_match_bitmap(PlannerInfo *root, List *clauses,
* we can use the collation for the attribute itself, as
* stored in varcollid. We do reset the statistics after a
* type change (including collation change), so this is OK.
* For expressions we use the collation extracted from the
* For expressions, we use the collation extracted from the
* expression itself.
*/
if (expronleft)
@@ -1805,8 +1808,8 @@ mcv_get_match_bitmap(PlannerInfo *root, List *clauses,
}
/*
* Stop evaluating the array elements once we reach match
* value that can't change - ALL() is the same as
* Stop evaluating the array elements once we reach a
* matching value that can't change - ALL() is the same as
* AND-list, ANY() is the same as OR-list.
*/
if (RESULT_IS_FINAL(match, expr->useOr))