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reftable: add merged table view
This adds an abstract, read-only interface to the ref database. This primitive is used to construct the read view of the ref database (the read view is constructed by merging several *.ref files). It also provides the mechanism to provide a unified view of the refs in the main repository and the per-worktree refs. Signed-off-by: Han-Wen Nienhuys <hanwen@google.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Han-Wen Nienhuys
committed by
Junio C Hamano
Junio C Hamano
parent
3b34f636df
commit
1ae2b8cda8
362
reftable/merged.c
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362
reftable/merged.c
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@@ -0,0 +1,362 @@
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/*
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Copyright 2020 Google LLC
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Use of this source code is governed by a BSD-style
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license that can be found in the LICENSE file or at
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https://developers.google.com/open-source/licenses/bsd
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*/
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#include "merged.h"
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#include "constants.h"
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#include "iter.h"
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#include "pq.h"
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#include "reader.h"
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#include "record.h"
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#include "generic.h"
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#include "reftable-merged.h"
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#include "reftable-error.h"
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#include "system.h"
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static int merged_iter_init(struct merged_iter *mi)
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{
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int i = 0;
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for (i = 0; i < mi->stack_len; i++) {
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struct reftable_record rec = reftable_new_record(mi->typ);
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int err = iterator_next(&mi->stack[i], &rec);
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if (err < 0) {
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return err;
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}
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if (err > 0) {
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reftable_iterator_destroy(&mi->stack[i]);
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reftable_record_destroy(&rec);
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} else {
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struct pq_entry e = {
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.rec = rec,
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.index = i,
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};
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merged_iter_pqueue_add(&mi->pq, e);
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}
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}
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return 0;
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}
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static void merged_iter_close(void *p)
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{
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struct merged_iter *mi = p;
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int i = 0;
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merged_iter_pqueue_release(&mi->pq);
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for (i = 0; i < mi->stack_len; i++) {
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reftable_iterator_destroy(&mi->stack[i]);
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}
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reftable_free(mi->stack);
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}
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static int merged_iter_advance_nonnull_subiter(struct merged_iter *mi,
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size_t idx)
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{
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struct reftable_record rec = reftable_new_record(mi->typ);
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struct pq_entry e = {
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.rec = rec,
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.index = idx,
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};
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int err = iterator_next(&mi->stack[idx], &rec);
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if (err < 0)
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return err;
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if (err > 0) {
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reftable_iterator_destroy(&mi->stack[idx]);
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reftable_record_destroy(&rec);
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return 0;
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}
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merged_iter_pqueue_add(&mi->pq, e);
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return 0;
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}
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static int merged_iter_advance_subiter(struct merged_iter *mi, size_t idx)
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{
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if (iterator_is_null(&mi->stack[idx]))
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return 0;
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return merged_iter_advance_nonnull_subiter(mi, idx);
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}
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static int merged_iter_next_entry(struct merged_iter *mi,
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struct reftable_record *rec)
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{
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struct strbuf entry_key = STRBUF_INIT;
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struct pq_entry entry = { 0 };
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int err = 0;
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if (merged_iter_pqueue_is_empty(mi->pq))
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return 1;
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entry = merged_iter_pqueue_remove(&mi->pq);
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err = merged_iter_advance_subiter(mi, entry.index);
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if (err < 0)
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return err;
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/*
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One can also use reftable as datacenter-local storage, where the ref
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database is maintained in globally consistent database (eg.
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CockroachDB or Spanner). In this scenario, replication delays together
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with compaction may cause newer tables to contain older entries. In
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such a deployment, the loop below must be changed to collect all
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entries for the same key, and return new the newest one.
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*/
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reftable_record_key(&entry.rec, &entry_key);
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while (!merged_iter_pqueue_is_empty(mi->pq)) {
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struct pq_entry top = merged_iter_pqueue_top(mi->pq);
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struct strbuf k = STRBUF_INIT;
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int err = 0, cmp = 0;
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reftable_record_key(&top.rec, &k);
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cmp = strbuf_cmp(&k, &entry_key);
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strbuf_release(&k);
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if (cmp > 0) {
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break;
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}
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merged_iter_pqueue_remove(&mi->pq);
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err = merged_iter_advance_subiter(mi, top.index);
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if (err < 0) {
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return err;
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}
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reftable_record_destroy(&top.rec);
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}
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reftable_record_copy_from(rec, &entry.rec, hash_size(mi->hash_id));
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reftable_record_destroy(&entry.rec);
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strbuf_release(&entry_key);
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return 0;
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}
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static int merged_iter_next(struct merged_iter *mi, struct reftable_record *rec)
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{
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while (1) {
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int err = merged_iter_next_entry(mi, rec);
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if (err == 0 && mi->suppress_deletions &&
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reftable_record_is_deletion(rec)) {
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continue;
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}
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return err;
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}
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}
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static int merged_iter_next_void(void *p, struct reftable_record *rec)
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{
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struct merged_iter *mi = p;
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if (merged_iter_pqueue_is_empty(mi->pq))
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return 1;
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return merged_iter_next(mi, rec);
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}
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static struct reftable_iterator_vtable merged_iter_vtable = {
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.next = &merged_iter_next_void,
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.close = &merged_iter_close,
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};
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static void iterator_from_merged_iter(struct reftable_iterator *it,
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struct merged_iter *mi)
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{
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assert(!it->ops);
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it->iter_arg = mi;
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it->ops = &merged_iter_vtable;
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}
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int reftable_new_merged_table(struct reftable_merged_table **dest,
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struct reftable_table *stack, int n,
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uint32_t hash_id)
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{
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struct reftable_merged_table *m = NULL;
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uint64_t last_max = 0;
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uint64_t first_min = 0;
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int i = 0;
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for (i = 0; i < n; i++) {
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uint64_t min = reftable_table_min_update_index(&stack[i]);
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uint64_t max = reftable_table_max_update_index(&stack[i]);
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if (reftable_table_hash_id(&stack[i]) != hash_id) {
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return REFTABLE_FORMAT_ERROR;
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}
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if (i == 0 || min < first_min) {
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first_min = min;
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}
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if (i == 0 || max > last_max) {
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last_max = max;
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}
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}
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m = reftable_calloc(sizeof(struct reftable_merged_table));
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m->stack = stack;
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m->stack_len = n;
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m->min = first_min;
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m->max = last_max;
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m->hash_id = hash_id;
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*dest = m;
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return 0;
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}
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/* clears the list of subtable, without affecting the readers themselves. */
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void merged_table_release(struct reftable_merged_table *mt)
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{
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FREE_AND_NULL(mt->stack);
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mt->stack_len = 0;
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}
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void reftable_merged_table_free(struct reftable_merged_table *mt)
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{
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if (!mt) {
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return;
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}
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merged_table_release(mt);
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reftable_free(mt);
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}
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uint64_t
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reftable_merged_table_max_update_index(struct reftable_merged_table *mt)
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{
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return mt->max;
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}
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uint64_t
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reftable_merged_table_min_update_index(struct reftable_merged_table *mt)
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{
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return mt->min;
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}
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static int reftable_table_seek_record(struct reftable_table *tab,
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struct reftable_iterator *it,
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struct reftable_record *rec)
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{
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return tab->ops->seek_record(tab->table_arg, it, rec);
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}
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static int merged_table_seek_record(struct reftable_merged_table *mt,
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struct reftable_iterator *it,
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struct reftable_record *rec)
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{
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struct reftable_iterator *iters = reftable_calloc(
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sizeof(struct reftable_iterator) * mt->stack_len);
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struct merged_iter merged = {
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.stack = iters,
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.typ = reftable_record_type(rec),
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.hash_id = mt->hash_id,
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.suppress_deletions = mt->suppress_deletions,
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};
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int n = 0;
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int err = 0;
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int i = 0;
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for (i = 0; i < mt->stack_len && err == 0; i++) {
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int e = reftable_table_seek_record(&mt->stack[i], &iters[n],
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rec);
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if (e < 0) {
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err = e;
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}
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if (e == 0) {
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n++;
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}
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}
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if (err < 0) {
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int i = 0;
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for (i = 0; i < n; i++) {
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reftable_iterator_destroy(&iters[i]);
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}
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reftable_free(iters);
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return err;
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}
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merged.stack_len = n;
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err = merged_iter_init(&merged);
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if (err < 0) {
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merged_iter_close(&merged);
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return err;
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} else {
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struct merged_iter *p =
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reftable_malloc(sizeof(struct merged_iter));
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*p = merged;
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iterator_from_merged_iter(it, p);
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}
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return 0;
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}
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int reftable_merged_table_seek_ref(struct reftable_merged_table *mt,
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struct reftable_iterator *it,
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const char *name)
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{
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struct reftable_ref_record ref = {
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.refname = (char *)name,
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};
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struct reftable_record rec = { NULL };
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reftable_record_from_ref(&rec, &ref);
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return merged_table_seek_record(mt, it, &rec);
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}
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int reftable_merged_table_seek_log_at(struct reftable_merged_table *mt,
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struct reftable_iterator *it,
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const char *name, uint64_t update_index)
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{
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struct reftable_log_record log = {
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.refname = (char *)name,
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.update_index = update_index,
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};
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struct reftable_record rec = { NULL };
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reftable_record_from_log(&rec, &log);
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return merged_table_seek_record(mt, it, &rec);
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}
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int reftable_merged_table_seek_log(struct reftable_merged_table *mt,
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struct reftable_iterator *it,
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const char *name)
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{
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uint64_t max = ~((uint64_t)0);
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return reftable_merged_table_seek_log_at(mt, it, name, max);
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}
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uint32_t reftable_merged_table_hash_id(struct reftable_merged_table *mt)
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{
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return mt->hash_id;
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}
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static int reftable_merged_table_seek_void(void *tab,
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struct reftable_iterator *it,
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struct reftable_record *rec)
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{
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return merged_table_seek_record(tab, it, rec);
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}
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static uint32_t reftable_merged_table_hash_id_void(void *tab)
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{
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return reftable_merged_table_hash_id(tab);
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}
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static uint64_t reftable_merged_table_min_update_index_void(void *tab)
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{
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return reftable_merged_table_min_update_index(tab);
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}
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static uint64_t reftable_merged_table_max_update_index_void(void *tab)
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{
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return reftable_merged_table_max_update_index(tab);
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}
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static struct reftable_table_vtable merged_table_vtable = {
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.seek_record = reftable_merged_table_seek_void,
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.hash_id = reftable_merged_table_hash_id_void,
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.min_update_index = reftable_merged_table_min_update_index_void,
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.max_update_index = reftable_merged_table_max_update_index_void,
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};
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void reftable_table_from_merged_table(struct reftable_table *tab,
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struct reftable_merged_table *merged)
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{
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assert(!tab->ops);
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tab->ops = &merged_table_vtable;
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tab->table_arg = merged;
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}
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