Function create_index_paths

src/backend/optimizer/path/indxpath.c:245–426

* create_index_paths() * Generate all interesting index paths for the given relation. * Candidate paths are added to the rel's pathlist (using add_path). * * To be considered for an index scan, an index must match one or more * restriction clauses or join clauses from the query's qual condition, * or match the query's ORDER BY condition, or have a predicate that * matches the query's qu

 * as meaning "unparameterized so far as the indexquals are concerned".
 */
void
create_index_paths(PlannerInfo *root, RelOptInfo *rel)
{
	List	   *indexpaths;
	List	   *bitindexpaths;
	List	   *bitjoinpaths;
	List	   *joinorclauses;
	IndexClauseSet rclauseset;
	IndexClauseSet jclauseset;
	IndexClauseSet eclauseset;
	ListCell   *lc;

	/* Skip the whole mess if no indexes */
	if (rel->indexlist == NIL)
		return;

	/* Bitmap paths are collected and then dealt with at the end */
	bitindexpaths = bitjoinpaths = joinorclauses = NIL;

	/* Examine each index in turn */
	foreach(lc, rel->indexlist)
	{
		IndexOptInfo *index = (IndexOptInfo *) lfirst(lc);

		/* Protect limited-size array in IndexClauseSets */
		Assert(index->nkeycolumns <= INDEX_MAX_KEYS);

		/*
		 * Ignore partial indexes that do not match the query.
		 * (generate_bitmap_or_paths() might be able to do something with
		 * them, but that's of no concern here.)
		 */
		if (index->indpred != NIL && !index->predOK)
			continue;

		/*
		 * Identify the restriction clauses that can match the index.
		 */
		MemSet(&rclauseset, 0, sizeof(rclauseset));
		match_restriction_clauses_to_index(root, index, &rclauseset);

		/*
		 * Build index paths from the restriction clauses.  These will be
		 * non-parameterized paths.  Plain paths go directly to add_path(),
		 * bitmap paths are added to bitindexpaths to be handled below.
		 */
		get_index_paths(root, rel, index, &rclauseset,
						&bitindexpaths);

		/*
		 * Identify the join clauses that can match the index.  For the moment
		 * we keep them separate from the restriction clauses.  Note that this
		 * step finds only "loose" join clauses that have not been merged into
		 * EquivalenceClasses.  Also, collect join OR clauses for later.
		 */
		MemSet(&jclauseset, 0, sizeof(jclauseset));
		match_join_clauses_to_index(root, rel, index,
									&jclauseset, &joinorclauses);