7c335b7a20
We have various requirements when using a dlist_head to keep track of the number of items in the list. This, traditionally, has been done by maintaining a counter variable in the calling code. Here we tidy this up by adding "dclist", which is very similar to dlist but also keeps track of the number of items stored in the list. Callers may use the new dclist_count() function when they need to know how many items are stored. Obtaining the count is an O(1) operation. For simplicity reasons, dclist and dlist both use dlist_node as their node type and dlist_iter/dlist_mutable_iter as their iterator type. dclists have all of the same functionality as dlists except there is no function named dclist_delete(). To remove an item from a list dclist_delete_from() must be used. This requires knowing which dclist the given item is stored in. Additionally, here we also convert some dlists where additional code exists to keep track of the number of items stored and to make these use dclists instead. Author: David Rowley Reviewed-by: Bharath Rupireddy, Aleksander Alekseev Discussion: https://postgr.es/m/CAApHDvrtVxr+FXEX0VbViCFKDGxA3tWDgw9oFewNXCJMmwLjLg@mail.gmail.com |
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| .. | ||
| Makefile | ||
| README | ||
| binaryheap.c | ||
| bipartite_match.c | ||
| bloomfilter.c | ||
| dshash.c | ||
| hyperloglog.c | ||
| ilist.c | ||
| integerset.c | ||
| knapsack.c | ||
| meson.build | ||
| pairingheap.c | ||
| rbtree.c | ||
README
This directory contains a general purpose data structures, for use anywhere in the backend: binaryheap.c - a binary heap bipartite_match.c - Hopcroft-Karp maximum cardinality algorithm for bipartite graphs bloomfilter.c - probabilistic, space-efficient set membership testing dshash.c - concurrent hash tables backed by dynamic shared memory areas hyperloglog.c - a streaming cardinality estimator ilist.c - single and double-linked lists integerset.c - a data structure for holding large set of integers knapsack.c - knapsack problem solver pairingheap.c - a pairing heap rbtree.c - a red-black tree stringinfo.c - an extensible string type Aside from the inherent characteristics of the data structures, there are a few practical differences between the binary heap and the pairing heap. The binary heap is fully allocated at creation, and cannot be expanded beyond the allocated size. The pairing heap on the other hand has no inherent maximum size, but the caller needs to allocate each element being stored in the heap, while the binary heap works with plain Datums or pointers. The linked-lists in ilist.c can be embedded directly into other structs, as opposed to the List interface in nodes/pg_list.h.