commit 8446db7cbcb42249b765d0090ca048178f3fc232
parent 8679c9f293483c47462ae53ae8a74d3fb7d9161a
Author: William Casarin <jb55@jb55.com>
Date: Tue, 28 Nov 2023 15:53:01 -0800
nostrdb/search: prepare text search for accurate phrase results
This patch sets the stage for phrase searching. It collects data into
result sets based on words and the word's associated key. We can use
this data to select the best search results based on adjacent
word_indices.
Signed-off-by: William Casarin <jb55@jb55.com>
Diffstat:
2 files changed, 321 insertions(+), 60 deletions(-)
diff --git a/nostrdb/nostrdb.c b/nostrdb/nostrdb.c
@@ -23,6 +23,9 @@
#include "secp256k1_ecdh.h"
#include "secp256k1_schnorrsig.h"
+#define max(a,b) ((a) > (b) ? (a) : (b))
+#define min(a,b) ((a) < (b) ? (a) : (b))
+
// the maximum number of things threads pop and push in bulk
static const int THREAD_QUEUE_BATCH = 4096;
@@ -135,15 +138,40 @@ struct ndb_u64_tsid {
uint64_t timestamp;
};
-// uncompressed form of the actual lmdb key
-struct ndb_text_search_key
+#define MAX_RESULTS_PER_WORD 32
+#define MAX_TEXT_SEARCH_WORDS 8
+
+// used mainly by ndb_text_search when collecting text search results
+struct ndb_keyed_text_search_result {
+ struct ndb_text_search_key key;
+ uint64_t note_id;
+ int prefix_chars;
+};
+
+struct ndb_keyed_text_search_resultset {
+ struct ndb_keyed_text_search_result results[MAX_RESULTS_PER_WORD];
+ int num_results;
+};
+
+struct ndb_word
{
- int str_len;
- const char *str;
- int word_index;
- uint64_t timestamp;
+ const char *word;
+ int word_len;
+};
+
+struct ndb_search_words
+{
+ struct ndb_word words[MAX_TEXT_SEARCH_WORDS];
+ int num_words;
};
+// used mainly by ndb_text_search when collecting text search results
+struct ndb_keyed_text_search_results {
+ struct ndb_keyed_text_search_resultset results[MAX_TEXT_SEARCH_WORDS];
+ int num_words;
+};
+
+
// ndb_text_search_key
//
// This is compressed when in lmdb:
@@ -260,30 +288,59 @@ static int ndb_text_search_key_compare(const MDB_val *a, const MDB_val *b)
return 0;
}
-/*
-static int ndb_decompress_text_search_key(unsigned char *p, int len,
- struct ndb_text_search_key *key)
+// faster peek of just the string instead of unpacking everything
+// this is used to quickly discard range query matches if there is no
+// common prefix
+static inline int ndb_unpack_text_search_key_string(struct cursor *cur,
+ const char **str,
+ int *str_len)
{
- struct cursor c;
+ if (!pull_varint(cur, str_len))
+ return 0;
- make_cursor(p, p + len, &c);
+ *str = (const char *)cur->p;
- if (!pull_varint(&c, &key->str_len))
+ if (!cursor_skip(cur, *str_len))
return 0;
+
+ return 1;
+}
- key->str = cur->p;
+// should be called after ndb_unpack_text_search_key_string. It continues
+// the unpacking of a text search key if we've already started it.
+static inline int
+ndb_unpack_remaining_text_search_key(struct cursor *cur,
+ struct ndb_text_search_key *key)
+{
+ int timestamp;
- if (!cursor_skip(&c, key->str_len))
+ if (!pull_varint(cur, &key->word_index))
return 0;
- if (!pull_varint(&c, &key->word_index))
+ if (!pull_varint(cur, ×tamp))
return 0;
- if (!pull_varint(&c, &key->timestamp))
+ key->timestamp = timestamp;
+
+ return 1;
+}
+
+// unpack a fulltext search key
+//
+// full version of string + unpack remaining. This is split up because text
+// searching only requires to pull the string for prefix searching, and the
+// remaining is optional
+static inline int ndb_unpack_text_search_key(unsigned char *p, int len,
+ struct ndb_text_search_key *key)
+{
+ struct cursor c;
+ make_cursor(p, p + len, &c);
+
+ if (!ndb_unpack_text_search_key_string(&c, &key->str, &key->str_len))
return 0;
+ return ndb_unpack_remaining_text_search_key(&c, key);
}
-*/
// Copies only lowercase characters to the destination string and fills the rest with null bytes.
// `dst` and `src` are pointers to the destination and source strings, respectively.
@@ -2224,6 +2281,9 @@ static int ndb_write_word_to_index(struct ndb_txn *txn, const char *word,
+// break a string into individual words for querying or for building the
+// fulltext search index. This is callback based so we don't need to
+// build up an intermediate structure
static int ndb_parse_words(struct cursor *cur, void *ctx, ndb_word_parser_fn fn)
{
int word_len, words;
@@ -2305,26 +2365,12 @@ static int ndb_write_note_fulltext_index(struct ndb_txn *txn,
return 1;
}
-struct ndb_word
-{
- const char *word;
- int word_len;
-};
-
-#define MAX_SEARCH_WORDS 16
-
-struct ndb_search_words
-{
- struct ndb_word words[MAX_SEARCH_WORDS];
- int num_words;
-};
-
static int ndb_parse_search_words(void *ctx, const char *word_str, int word_len, int word_index)
{
struct ndb_search_words *words = ctx;
struct ndb_word *word;
- if (words->num_words + 1 > MAX_SEARCH_WORDS)
+ if (words->num_words + 1 > MAX_TEXT_SEARCH_WORDS)
return 0;
word = &words->words[words->num_words++];
@@ -2334,40 +2380,214 @@ static int ndb_parse_search_words(void *ctx, const char *word_str, int word_len,
return 1;
}
-int ndb_text_search(struct ndb_txn *txn, const char *query)
+static void ndb_keyed_text_search_results_init(struct ndb_keyed_text_search_results *r)
+{
+ r->num_words = 0;
+}
+
+static void ndb_search_words_init(struct ndb_search_words *words)
+{
+ words->num_words = 0;
+}
+
+
+static int prefix_count(const char *str1, int len1, const char *str2, int len2) {
+ int i, count = 0;
+ int min_len = len1 < len2 ? len1 : len2;
+
+ for (i = 0; i < min_len; i++) {
+ // case insensitive
+ if (tolower(str1[i]) == tolower(str2[i]))
+ count++;
+ else
+ break;
+ }
+
+ return count;
+}
+
+
+// This is called when scanning the full text search index. Scanning stops
+// when we no longer have a prefix match for the word
+static int ndb_text_search_next_word(MDB_cursor *cursor, MDB_cursor_op op,
+ MDB_val *k, MDB_val *v, struct ndb_word *search_word,
+ struct ndb_keyed_text_search_resultset *results)
+{
+ struct ndb_keyed_text_search_result *result;
+ struct cursor key_cursor;
+
+ make_cursor(k->mv_data, k->mv_data + k->mv_size, &key_cursor);
+
+ // if we won't have enough to store the result, then bail
+ if (results->num_results + 1 > MAX_RESULTS_PER_WORD)
+ return 0;
+
+ // place to store the results if we get a successful one. num_results
+ // is incremented at the end if so
+ result = &results->results[results->num_results];
+
+ // When op is MDB_SET_RANGE, this initializes the search. Position
+ // the cursor at the next key greater than or equal to the specified
+ // key.
+ //
+ // Subsequent searches should use MDB_NEXT
+ if (mdb_cursor_get(cursor, k, v, op))
+ return 0;
+
+ result->note_id = *((uint64_t*)v->mv_data);
+
+ // On success, this could still be not related at all.
+ // It could just be adjacent to the word. Let's check
+ // if we have a matching prefix at least.
+
+ // Before we unpack the entire key, let's quickly
+ // unpack just the string to check the prefix. We don't
+ // need to unpack the entire key if the prefix doesn't
+ // match
+ make_cursor(k->mv_data, k->mv_data + k->mv_size, &key_cursor);
+ if (!ndb_unpack_text_search_key_string(&key_cursor,
+ &result->key.str,
+ &result->key.str_len)) {
+ // this should never happen
+ fprintf(stderr, "UNUSUAL: failed to unpack text search key string\n");
+ return 0;
+ }
+
+ // Empty strings shouldn't happen but let's
+ // protect against these cases
+ if (result->key.str_len < 1)
+ return 0;
+
+ // make sure we at least have a matching prefix. exact
+ // matches are nice but range searches allow us to
+ // match prefixes as well. A single-char prefix is
+ // suffient, but maybe we could up this in the future.
+ //
+ // TODO: How are we handling utf-8 prefix matches like
+ // japanese?
+ //
+ if (result->key.str[0] != tolower(search_word->word[0]))
+ return 0;
+
+ // count the number of prefix-matched characters. This will be used
+ // for ranking search results
+ result->prefix_chars = prefix_count(result->key.str,
+ result->key.str_len,
+ search_word->word,
+ search_word->word_len);
+
+ // Unpack the remaining text search key, we will need this information
+ // when building up our search results.
+ if (!ndb_unpack_remaining_text_search_key(&key_cursor, &result->key)) {
+ // This should never happen
+ fprintf(stderr, "UNUSUAL: failed to unpack text search key\n");
+ return 0;
+ }
+
+ // let's actually register this result now. the key has already been
+ // fully unpacked
+ results->num_results++;
+
+ return 1;
+}
+
+static void ndb_print_text_search_key(struct ndb_text_search_key *key)
+{
+ fprintf(stderr, "K<'%.*s' %d %" PRIu64 ">", key->str_len, key->str,
+ key->word_index,
+ key->timestamp);
+}
+
+static void ndb_print_keyed_text_search_result(struct ndb_keyed_text_search_result *r)
+{
+ ndb_print_text_search_key(&r->key);
+ fprintf(stderr, " note_id:%" PRIu64 "\n", r->note_id);
+}
+
+// convert the keyed results into actual results that include phrase results.
+// This works by looping over all of the results
+static int ndb_process_text_search_results(
+ struct ndb_keyed_text_search_results *keyed_results,
+ struct ndb_text_search_results *results)
+{
+ int i, j;
+ struct ndb_keyed_text_search_resultset *resultset;
+ struct ndb_keyed_text_search_result *result;
+
+ // Phrase search. Find keyed adjacent keyed search results
+ for (i = 0; i < keyed_results->num_words; i++) {
+ resultset = &keyed_results->results[i];
+ for (j = 0; j < resultset->num_results; j++) {
+ result = &resultset->results[j];
+ ndb_print_keyed_text_search_result(result);
+ }
+ }
+
+ return 1;
+}
+
+static void ndb_keyed_text_search_resultset_init(
+ struct ndb_keyed_text_search_resultset *resultset) {
+ resultset->num_results = 0;
+}
+
+static void ndb_text_search_results_init(struct ndb_text_search_results *res)
+{
+ res->num_phrase_results = 0;
+ res->num_other_results = 0;
+}
+
+int ndb_text_search(struct ndb_txn *txn, const char *query,
+ struct ndb_text_search_results *results)
{
unsigned char buffer[1024];
- struct ndb_search_words words;
- struct ndb_word *word;
+ struct ndb_keyed_text_search_results keyed_results;
+ struct ndb_keyed_text_search_resultset *keyed_resultset;
+ struct ndb_search_words search_words;
+ struct ndb_word *search_word;
struct cursor cur;
MDB_dbi text_db;
MDB_cursor *cursor;
MDB_val k, v;
- int i, rc, keysize;
- size_t len;
- //uint64_t note_ids[32], note_id;
- uint64_t note_id;
- struct ndb_note *note;
+ int i, j, keysize, num_words;
+ MDB_cursor_op op = MDB_SET_RANGE;
//int num_note_ids;
+
+ ndb_keyed_text_search_results_init(&keyed_results);
+ ndb_text_search_results_init(results);
+ ndb_search_words_init(&search_words);
//num_note_ids = 0;
text_db = txn->lmdb->dbs[NDB_DB_NOTE_TEXT];
make_cursor((unsigned char *)query, (unsigned char *)query + strlen(query), &cur);
- words.num_words = 0;
- ndb_parse_words(&cur, &words, ndb_parse_search_words);
+ ndb_parse_words(&cur, &search_words, ndb_parse_search_words);
- if ((rc = mdb_cursor_open(txn->mdb_txn, text_db, &cursor))) {
- fprintf(stderr, "nd_text_search: mdb_cursor_open failed, error %d\n", rc);
+ if ((i = mdb_cursor_open(txn->mdb_txn, text_db, &cursor))) {
+ fprintf(stderr, "nd_text_search: mdb_cursor_open failed, error %d\n", i);
return 0;
}
- for (i = 0; i < words.num_words; i++) {
- word = &words.words[i];
- fprintf(stderr, "search word %.*s\n", word->word_len, word->word);
+ fprintf(stderr, "search query: '%s'\n", query);
+
+ // number of actual result words
+ // for every search word up to a max of MAX_TEXT_SEARCH_WORDS words (8)
+
+ num_words = min(search_words.num_words, MAX_TEXT_SEARCH_WORDS);
+ for (i = 0; i < num_words; i++) {
+ search_word = &search_words.words[i];
+
+ // shouldn't happen but let's be defensive a bit
+ if (search_word->word_len == 0)
+ continue;
+
+ // construct a packed fulltext search key using this word
+ // this key doesn't contain any timestamp or index info,
+ // so it should range match instead of exact match
if (!ndb_make_text_search_key_low(buffer, sizeof(buffer),
- word->word_len, word->word,
+ search_word->word_len,
+ search_word->word,
&keysize)) {
// word is too big to fit in 1024-sized key
continue;
@@ -2375,22 +2595,41 @@ int ndb_text_search(struct ndb_txn *txn, const char *query)
k.mv_data = buffer;
k.mv_size = keysize;
+ op = MDB_SET_RANGE;
- // Position cursor at the next key greater than or equal to the specified key
- if (mdb_cursor_get(cursor, &k, &v, MDB_SET_RANGE)) {
- continue;
- } else {
- //note_ids[num_note_ids++] = *((uint64_t*)v.mv_data);
- note_id = *((uint64_t*)v.mv_data);
- if ((note = ndb_get_note_by_key(txn, note_id, &len))) {
- fprintf(stderr, "found note: '%s' for query word '%.*s'\n",
- ndb_note_str(note, ¬e->content).str,
- word->word_len, word->word);
+ keyed_resultset = &keyed_results.results[keyed_results.num_words];
+ ndb_keyed_text_search_resultset_init(keyed_resultset);
+
+ // try to match the word as many times as possible before
+ // moving on to the next word
+ for (j = 0; j < MAX_RESULTS_PER_WORD; j++)
+ {
+ if (!ndb_text_search_next_word(cursor, op, &k, &v,
+ search_word,
+ keyed_resultset)) {
+ break;
}
- return 1;
+
+ op = MDB_NEXT;
+ }
+
+ if (keyed_resultset->num_results > 0)
+ keyed_results.num_words++;
+
+ /*
+ if ((note = ndb_get_note_by_key(txn, note_id, &len))) {
+ fprintf(stderr, "found note: '%s' for query word '%.*s'\n",
+ ndb_note_str(note, ¬e->content).str,
+ word->word_len, word->word);
}
+ */
}
+ // convert our keyed results into
+ ndb_process_text_search_results(&keyed_results, results);
+
+ mdb_cursor_close(cursor);
+
return 1;
}
@@ -4025,3 +4264,5 @@ inline int ndb_builder_push_tag_str(struct ndb_builder *builder,
return 0;
return ndb_builder_finalize_tag(builder, pstr);
}
+
+
diff --git a/nostrdb/nostrdb.h b/nostrdb/nostrdb.h
@@ -270,6 +270,26 @@ struct ndb_filter {
struct ndb_filter_elements *elements[NDB_NUM_FILTERS];
};
+// unpacked form of the actual lmdb fulltext search key
+// see `ndb_make_text_search_key` for how the packed version is constructed
+struct ndb_text_search_key
+{
+ int str_len;
+ const char *str;
+ int word_index;
+ uint64_t timestamp;
+};
+
+// contains note ids of the searched notes from ndb_text_search
+struct ndb_text_search_results {
+ uint64_t phrase_results[32];
+ int num_phrase_results;
+
+ uint64_t other_results[32];
+ int num_other_results;
+};
+
+
// HELPERS
int ndb_calculate_id(struct ndb_note *note, unsigned char *buf, int buflen);
int ndb_sign_id(struct ndb_keypair *keypair, unsigned char id[32], unsigned char sig[64]);
@@ -330,7 +350,7 @@ void ndb_filter_free(struct ndb_filter *filter);
// FULLTEXT SEARCH
-int ndb_text_search(struct ndb_txn *, const char *query);
+int ndb_text_search(struct ndb_txn *txn, const char *query, struct ndb_text_search_results *);
// stats
int ndb_stat(struct ndb *ndb, struct ndb_stat *stat);
