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https://github.com/HypoPG/hypopg
synced 2026-05-24 09:38:21 +00:00
Handle a better btree index size estimation.
The index property (tuples, pages and tree_height) is now in a dedicated function. There's also now a SQL function that can show the estimated index size, according to current relted relation stats. The pages estimation could still be greatly improved. The tree_hight is also hard-coded to -1 (unknown) for now.
This commit is contained in:
Julien Rouhaud
parent
7011da6ad4
commit
14134802e6
2 changed files with 156 additions and 14 deletions
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@ -92,3 +92,9 @@ $_$
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) src;
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$_$
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LANGUAGE sql;
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CREATE FUNCTION
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hypopg_relation_size(IN indexid Oid)
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RETURNS bigint
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LANGUAGE c COST 100
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AS '$libdir/hypopg', 'hypopg_relation_size';
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164
hypopg.c
164
hypopg.c
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@ -13,6 +13,9 @@
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#if PG_VERSION_NUM >= 90300
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#include "access/htup_details.h"
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#endif
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#include "access/nbtree.h"
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#include "access/sysattr.h"
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#include "access/xlog.h"
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#include "catalog/catalog.h"
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#include "catalog/heap.h"
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#include "catalog/namespace.h"
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@ -54,6 +57,10 @@ typedef struct hypoEntry
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Oid reltablespace; /* tablespace of the index, if set */
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char *indexname; /* hypothetical index name */
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BlockNumber pages; /* number of estimated disk pages for the index */
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double tuples; /* number of estimated tuples in the index */
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int tree_height; /* estimated index tree height, -1 if unknown */
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/* index descriptor informations */
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int ncolumns; /* number of columns, only 1 for now */
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short int *indexkeys; /* attnums */
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@ -97,12 +104,14 @@ Datum hypopg_add_index_internal(PG_FUNCTION_ARGS);
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Datum hypopg(PG_FUNCTION_ARGS);
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Datum hypopg_create_index(PG_FUNCTION_ARGS);
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Datum hypopg_drop_index(PG_FUNCTION_ARGS);
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Datum hypopg_relation_size(PG_FUNCTION_ARGS);
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PG_FUNCTION_INFO_V1(hypopg_reset);
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PG_FUNCTION_INFO_V1(hypopg_add_index_internal);
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PG_FUNCTION_INFO_V1(hypopg);
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PG_FUNCTION_INFO_V1(hypopg_create_index);
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PG_FUNCTION_INFO_V1(hypopg_drop_index);
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PG_FUNCTION_INFO_V1(hypopg_relation_size);
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static hypoEntry * newHypoEntry(Oid relid, char *accessMethod, int ncolumns);
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static Oid hypoGetNewOid(Oid relid);
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@ -152,6 +161,9 @@ static void injectHypotheticalIndex(PlannerInfo *root,
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static bool hypo_query_walker(Node *node);
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static void hypo_set_indexname(hypoEntry *entry, char* indexname);
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static void hypo_estimate_index_simple(hypoEntry *entry,
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BlockNumber *pages, double *tuples);
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static void hypo_estimate_index(hypoEntry *entry, RelOptInfo *rel);
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static List * build_index_tlist(PlannerInfo *root, IndexOptInfo *index,
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Relation heapRelation);
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@ -252,7 +264,7 @@ newHypoEntry(Oid relid, char *accessMethod, int ncolumns)
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break;
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default:
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/* do not store hypothetical indexes with access method not supported */
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elog(ERROR, "pg_hypo: access method %d is not supported",
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elog(ERROR, "hypopg: access method %d is not supported",
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entry->relam);
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break;
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}
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@ -621,9 +633,6 @@ injectHypotheticalIndex(PlannerInfo *root,
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if (index->relam == BTREE_AM_OID)
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{
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#if PG_VERSION_NUM >= 90300
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index->tree_height = 1; // TODO
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#endif
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index->sortopfamily = index->opfamily;
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}
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@ -648,16 +657,16 @@ injectHypotheticalIndex(PlannerInfo *root,
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/* Build targetlist using the completed indexprs data, copied from PostgreSQL */
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index->indextlist = build_index_tlist(root, index, relation);
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if (index->indpred == NIL)
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{
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/* very quick and pessimistic estimation:
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* number of tuples * avg width,
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* with ~ 50% bloat (including 10% fillfactor), plus 1 block
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*/
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index->pages = (rel->tuples * ind_avg_width * 2 / BLCKSZ) + 1;
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/* partial index not supported yet, so assume all tuples are in the index */
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index->tuples = rel->tuples;
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}
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/* estimate most of the hypothyetical index stuff, more exactly
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* - tuples
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* - pages
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* - tree_height
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*/
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hypo_estimate_index(entry, rel);
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index->pages = entry->pages;
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index->tuples = entry->tuples;
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index->tree_height = entry->tree_height;
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/* obviously, setup this tag.
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* However, it's only checked in selfuncs.c/get_actual_variable_range, so
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@ -876,6 +885,32 @@ hypopg_drop_index(PG_FUNCTION_ARGS)
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PG_RETURN_BOOL(entry_remove(indexid));
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}
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/*
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* SQL Wrapper around the hypothetical index size estimation
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*/
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Datum
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hypopg_relation_size(PG_FUNCTION_ARGS)
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{
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BlockNumber pages;
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double tuples;
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Oid indexid = PG_GETARG_OID(0);
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ListCell *lc;
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pages = 0;
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tuples = 0;
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foreach(lc, entries)
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{
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hypoEntry *entry = (hypoEntry *) lfirst(lc);
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if (entry->oid == indexid)
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{
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hypo_estimate_index_simple(entry, &pages, &tuples);
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}
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}
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PG_RETURN_INT64(pages * BLCKSZ);
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}
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/* Simple function to set the indexname, dealing with the ending \0 and correct
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* palloc size
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*/
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@ -893,6 +928,107 @@ hypo_set_indexname(hypoEntry *entry, char* indexname)
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strncpy(entry->indexname, indexname, strlen(indexname) + 1);
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}
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/*
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* Fill the pages and tuples information for a given hypoentry.
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*/
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static void
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hypo_estimate_index_simple(hypoEntry *entry, BlockNumber *pages, double *tuples)
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{
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RelOptInfo *rel;
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Relation relation;
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/* retrieve number of tuples and pages of the related relation, adapted
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* from plancat.c/get_relation_info().
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*/
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rel = makeNode(RelOptInfo);
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relation = heap_open(entry->relid, AccessShareLock);
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if (!RelationNeedsWAL(relation) && RecoveryInProgress())
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ereport(ERROR,
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(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
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errmsg("hypopg: cannot access temporary or unlogged relations during recovery")));
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rel->min_attr = FirstLowInvalidHeapAttributeNumber + 1;
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rel->max_attr = RelationGetNumberOfAttributes(relation);
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rel->reltablespace = RelationGetForm(relation)->reltablespace;
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estimate_rel_size(relation, rel->attr_widths - rel->min_attr,
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&rel->pages, &rel->tuples, &rel->allvisfrac);
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heap_close(relation, NoLock);
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hypo_estimate_index(entry, rel);
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*pages = entry->pages;
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*tuples = entry->tuples;
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}
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/*
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* Fill the pages and tuples information for a given hypoentry and a given
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* RelOptInfo
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*/
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static void
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hypo_estimate_index(hypoEntry *entry, RelOptInfo *rel)
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{
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int i, ind_avg_width = 0;
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int usable_page_size;
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int line_size;
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double bloat_factor;
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int additional_bloat = 20;
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for (i=0; i< entry->ncolumns; i++)
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{
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ind_avg_width += get_attavgwidth(entry->relid, entry->indexkeys[i]);
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}
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/*
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* TODO: handle here when indpred and indexpres will be added, and
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* other access methods
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*/
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switch (entry->relam)
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{
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case BTREE_AM_OID:
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/* Will need to change this when handling predicate */
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entry->tuples = rel->tuples;
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/*
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* quick estimating of index size:
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*
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* sizeof(PageHeader) : 24 (1 per page)
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* sizeof(BTPageOpaqueData): 16 (1 per page)
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* sizeof(IndexTupleData): 8 (1 per tuple, referencing heap)
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* sizeof(ItemIdData): 4 (1 per tuple, storing the index item)
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* default fillfactor: 90%
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* no NULL handling
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* fixed additional bloat: 20%
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*
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* I'll also need to read more carefully nbtree code to check is
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* this is accurate enough.
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*
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*/
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line_size = ind_avg_width +
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+ (sizeof(IndexTupleData) * entry->ncolumns)
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+ MAXALIGN(sizeof(ItemIdData) * entry->ncolumns);
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usable_page_size = BLCKSZ - sizeof(PageHeaderData) - sizeof(BTPageOpaqueData);
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bloat_factor = (200.0 - BTREE_DEFAULT_FILLFACTOR + additional_bloat) / 100;
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entry->pages =
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entry->tuples * line_size * bloat_factor / usable_page_size;
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#if PG_VERSION_NUM >= 90300
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entry->tree_height = -1; // TODO
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#endif
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break;
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default:
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elog(WARNING, "hypopg: access method %d is not supported",
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entry->relam);
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}
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}
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/* Copied from backend/optimizer/util/plancat.c, not exported.
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*
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* Build a targetlist representing the columns of the specified index.
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