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Implemented lfsr_rbyd_namelookup as a binary search, dropped search in fetch

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Originally I thought doing a linear search during fetch was going to be
the best route for name lookups, since we already needed a O(b) fetch,
which set a hard ceiling for name lookup performance.

But it turns out we don't need to fetch during btree name lookups
unless we're also validating! Now that validation and lookups are
disentangled, we can do a binary search over the rbyd to drop our
name lookup down to O(log(b)^2).

Two other motivations for this change:

1. This removes the name search from lfsr_rbyd_fetch, which has been
   surprisingly tricky to get right.

2. Now that lfsr_rbyd_fetch doesn't need to follow the create/delete
   history to find and reconstruct the state of names, we only need to
   know the create/delete state of tags post-fetch, freeing up the rbyd
   encoding to be more flexible.

   The next thing I plan to do is drop on-disk remove tags, for example.

This drops the total btree namelookup cost from O(b log_b(n)) to
O(log(b)^2 log_b(n)).
This commit is contained in:
Christopher Haster
2023-06-16 14:43:47 -05:00
parent 2113d877d6
commit aa559d30b0
3 changed files with 335 additions and 391 deletions
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tests/test_btree.toml
+44 -44
View File
@@ -2853,8 +2853,8 @@ code = '''
lfs_size_t weight_;
lfsr_data_t data_;
lfsr_btree_namelookupnext(&lfs, &btree, "aaa", 3,
&id_, NULL, NULL, &tag_, &weight_, &data_) => LFS_ERR_NOENT;
lfsr_btree_namelookup(&lfs, &btree, "aaa", 3,
&id_, &tag_, &weight_, &data_) => LFS_ERR_NOENT;
'''
[cases.test_btree_find_one]
@@ -2887,16 +2887,16 @@ code = '''
lfs_size_t weight_;
lfsr_data_t data_;
lfsr_btree_namelookupnext(&lfs, &btree, "aaa", 3,
&id_, NULL, NULL, &tag_, &weight_, &data_) => 0;
lfsr_btree_namelookup(&lfs, &btree, "aaa", 3,
&id_, &tag_, &weight_, &data_) => 0;
assert(tag_ == LFSR_TAG_INLINED);
assert(id_ == 0);
assert(weight_ == 1);
lfsr_data_read(&lfs, data_, 0, buffer, 4) => 1;
assert(memcmp(buffer, "0", 1) == 0);
lfsr_btree_namelookupnext(&lfs, &btree, "aab", 3,
&id_, NULL, NULL, &tag_, &weight_, &data_) => 0;
lfsr_btree_namelookup(&lfs, &btree, "aab", 3,
&id_, &tag_, &weight_, &data_) => 0;
assert(tag_ == LFSR_TAG_INLINED);
assert(id_ == 0);
assert(weight_ == 1);
@@ -2937,24 +2937,24 @@ code = '''
lfs_size_t weight_;
lfsr_data_t data_;
lfsr_btree_namelookupnext(&lfs, &btree, "aaa", 3,
&id_, NULL, NULL, &tag_, &weight_, &data_) => 0;
lfsr_btree_namelookup(&lfs, &btree, "aaa", 3,
&id_, &tag_, &weight_, &data_) => 0;
assert(tag_ == LFSR_TAG_INLINED);
assert(id_ == 0);
assert(weight_ == 1);
lfsr_data_read(&lfs, data_, 0, buffer, 4) => 1;
assert(memcmp(buffer, "0", 1) == 0);
lfsr_btree_namelookupnext(&lfs, &btree, "aab", 3,
&id_, NULL, NULL, &tag_, &weight_, &data_) => 0;
lfsr_btree_namelookup(&lfs, &btree, "aab", 3,
&id_, &tag_, &weight_, &data_) => 0;
assert(tag_ == LFSR_TAG_INLINED);
assert(id_ == 1);
assert(weight_ == 1);
lfsr_data_read(&lfs, data_, 0, buffer, 4) => 1;
assert(memcmp(buffer, "1", 1) == 0);
lfsr_btree_namelookupnext(&lfs, &btree, "aac", 3,
&id_, NULL, NULL, &tag_, &weight_, &data_) => 0;
lfsr_btree_namelookup(&lfs, &btree, "aac", 3,
&id_, &tag_, &weight_, &data_) => 0;
assert(tag_ == LFSR_TAG_INLINED);
assert(id_ == 1);
assert(weight_ == 1);
@@ -2998,32 +2998,32 @@ code = '''
lfs_size_t weight_;
lfsr_data_t data_;
lfsr_btree_namelookupnext(&lfs, &btree, "aaa", 3,
&id_, NULL, NULL, &tag_, &weight_, &data_) => 0;
lfsr_btree_namelookup(&lfs, &btree, "aaa", 3,
&id_, &tag_, &weight_, &data_) => 0;
assert(tag_ == LFSR_TAG_INLINED);
assert(id_ == 0);
assert(weight_ == 1);
lfsr_data_read(&lfs, data_, 0, buffer, 4) => 1;
assert(memcmp(buffer, "0", 1) == 0);
lfsr_btree_namelookupnext(&lfs, &btree, "aab", 3,
&id_, NULL, NULL, &tag_, &weight_, &data_) => 0;
lfsr_btree_namelookup(&lfs, &btree, "aab", 3,
&id_, &tag_, &weight_, &data_) => 0;
assert(tag_ == LFSR_TAG_INLINED);
assert(id_ == 1);
assert(weight_ == 1);
lfsr_data_read(&lfs, data_, 0, buffer, 4) => 1;
assert(memcmp(buffer, "1", 1) == 0);
lfsr_btree_namelookupnext(&lfs, &btree, "aac", 3,
&id_, NULL, NULL, &tag_, &weight_, &data_) => 0;
lfsr_btree_namelookup(&lfs, &btree, "aac", 3,
&id_, &tag_, &weight_, &data_) => 0;
assert(tag_ == LFSR_TAG_INLINED);
assert(id_ == 2);
assert(weight_ == 1);
lfsr_data_read(&lfs, data_, 0, buffer, 4) => 1;
assert(memcmp(buffer, "2", 1) == 0);
lfsr_btree_namelookupnext(&lfs, &btree, "aad", 3,
&id_, NULL, NULL, &tag_, &weight_, &data_) => 0;
lfsr_btree_namelookup(&lfs, &btree, "aad", 3,
&id_, &tag_, &weight_, &data_) => 0;
assert(tag_ == LFSR_TAG_INLINED);
assert(id_ == 2);
assert(weight_ == 1);
@@ -3067,32 +3067,32 @@ code = '''
lfs_size_t weight_;
lfsr_data_t data_;
lfsr_btree_namelookupnext(&lfs, &btree, "aaa", 3,
&id_, NULL, NULL, &tag_, &weight_, &data_) => 0;
lfsr_btree_namelookup(&lfs, &btree, "aaa", 3,
&id_, &tag_, &weight_, &data_) => 0;
assert(tag_ == LFSR_TAG_INLINED);
assert(id_ == 0);
assert(weight_ == 1);
lfsr_data_read(&lfs, data_, 0, buffer, 4) => 1;
assert(memcmp(buffer, "0", 1) == 0);
lfsr_btree_namelookupnext(&lfs, &btree, "aab", 3,
&id_, NULL, NULL, &tag_, &weight_, &data_) => 0;
lfsr_btree_namelookup(&lfs, &btree, "aab", 3,
&id_, &tag_, &weight_, &data_) => 0;
assert(tag_ == LFSR_TAG_INLINED);
assert(id_ == 1);
assert(weight_ == 1);
lfsr_data_read(&lfs, data_, 0, buffer, 4) => 1;
assert(memcmp(buffer, "1", 1) == 0);
lfsr_btree_namelookupnext(&lfs, &btree, "aac", 3,
&id_, NULL, NULL, &tag_, &weight_, &data_) => 0;
lfsr_btree_namelookup(&lfs, &btree, "aac", 3,
&id_, &tag_, &weight_, &data_) => 0;
assert(tag_ == LFSR_TAG_INLINED);
assert(id_ == 2);
assert(weight_ == 1);
lfsr_data_read(&lfs, data_, 0, buffer, 4) => 1;
assert(memcmp(buffer, "2", 1) == 0);
lfsr_btree_namelookupnext(&lfs, &btree, "aad", 3,
&id_, NULL, NULL, &tag_, &weight_, &data_) => 0;
lfsr_btree_namelookup(&lfs, &btree, "aad", 3,
&id_, &tag_, &weight_, &data_) => 0;
assert(tag_ == LFSR_TAG_INLINED);
assert(id_ == 2);
assert(weight_ == 1);
@@ -3153,8 +3153,8 @@ code = '''
alphas[(i/26/26) % 26], alphas[(i/26) % 26], alphas[i % 26]
};
lfsr_btree_namelookupnext(&lfs, &btree, name, 3,
&id_, NULL, NULL, &tag_, &weight_, &data_) => 0;
lfsr_btree_namelookup(&lfs, &btree, name, 3,
&id_, &tag_, &weight_, &data_) => 0;
assert(tag_ == LFSR_TAG_INLINED);
assert(id_ == i);
assert(weight_ == 1);
@@ -3268,8 +3268,8 @@ code = '''
lfs_size_t weight_;
lfsr_data_t data_;
for (lfs_size_t i = 0; i < sim_size; i++) {
lfsr_btree_namelookupnext(&lfs, &btree, sim_names[i], 3,
&id_, NULL, NULL, &tag_, &weight_, &data_) => 0;
lfsr_btree_namelookup(&lfs, &btree, sim_names[i], 3,
&id_, &tag_, &weight_, &data_) => 0;
assert(tag_ == LFSR_TAG_INLINED);
assert(id_ == i);
assert(weight_ == 1);
@@ -3339,8 +3339,8 @@ code = '''
alphas[(i/26/26) % 26], alphas[(i/26) % 26], alphas[i % 26]
};
lfsr_btree_namelookupnext(&lfs, &btree, name, 3,
&id_, NULL, NULL, &tag_, &weight_, &data_) => 0;
lfsr_btree_namelookup(&lfs, &btree, name, 3,
&id_, &tag_, &weight_, &data_) => 0;
assert(tag_ == LFSR_TAG_INLINED);
assert(id_ == i*W+W-1);
assert(weight_ == W);
@@ -3493,8 +3493,8 @@ code = '''
weighted_id += sim_weights[j];
}
lfsr_btree_namelookupnext(&lfs, &btree, sim_names[i], 3,
&id_, NULL, NULL, &tag_, &weight_, &data_) => 0;
lfsr_btree_namelookup(&lfs, &btree, sim_names[i], 3,
&id_, &tag_, &weight_, &data_) => 0;
assert(tag_ == LFSR_TAG_INLINED);
assert(id_ == weighted_id+sim_weights[i]-1);
assert(weight_ == sim_weights[i]);
@@ -3584,8 +3584,8 @@ code = '''
// split btree
lfs_size_t split_id;
lfsr_data_t split_data;
lfsr_btree_namelookupnext(&lfs, &btree, name, 3,
&split_id, NULL, NULL, NULL, NULL, &split_data) => 0;
lfsr_btree_namelookup(&lfs, &btree, name, 3,
&split_id, NULL, NULL, &split_data) => 0;
uint8_t split_buf[4];
lfsr_data_read(&lfs, split_data, 0, split_buf, 4) => 1;
if (split_id > id) {
@@ -3680,8 +3680,8 @@ code = '''
lfs_size_t weight_;
lfsr_data_t data_;
for (lfs_size_t i = 0; i < sim_size; i++) {
lfsr_btree_namelookupnext(&lfs, &btree, sim_names[i], 3,
&id_, NULL, NULL, &tag_, &weight_, &data_) => 0;
lfsr_btree_namelookup(&lfs, &btree, sim_names[i], 3,
&id_, &tag_, &weight_, &data_) => 0;
assert(tag_ == LFSR_TAG_INLINED);
assert(id_ == i);
assert(weight_ == 1);
@@ -3787,8 +3787,8 @@ code = '''
lfs_size_t split_id;
lfs_size_t split_weight;
lfsr_data_t split_data;
lfsr_btree_namelookupnext(&lfs, &btree, name, 3,
&split_id, NULL, NULL, NULL, &split_weight,
lfsr_btree_namelookup(&lfs, &btree, name, 3,
&split_id, NULL, &split_weight,
&split_data) => 0;
uint8_t split_buf[4];
lfsr_data_read(&lfs, split_data, 0, split_buf, 4) => 1;
@@ -3912,8 +3912,8 @@ code = '''
weighted_id += sim_weights[j];
}
lfsr_btree_namelookupnext(&lfs, &btree, sim_names[i], 3,
&id_, NULL, NULL, &tag_, &weight_, &data_) => 0;
lfsr_btree_namelookup(&lfs, &btree, sim_names[i], 3,
&id_, &tag_, &weight_, &data_) => 0;
assert(tag_ == LFSR_TAG_INLINED);
assert(id_ == weighted_id+sim_weights[i]-1);
assert(weight_ == sim_weights[i]);
tests/test_rbyd.toml
+183 -205
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