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In computer science, a substring index is a data structure which gives substring search in a text or text collection in sublinear time. Once constructed from a document or set of documents, a substring index can be used to locate all occurrences of a pattern in time linear or near-linear in the pattern size, with no dependence or only logarithmic dependence on the document size.
Reserved words in SQL and related products In SQL:2023 [3] In IBM Db2 13 [4] In Mimer SQL 11.0 [5] In MySQL 8.0 [6] In Oracle Database 23c [7] In PostgreSQL 16 [1] In Microsoft SQL Server 2022 [2]
The suffix array of the string is an array of n integers in the range of 0 to n that represents the n+1 suffixes of the string including the special character #. The suffix array is composed of two arrays: pos array pos[1,...n]: It represents a sorted list of all S suffixes.
Searching for this string in a database with a trigram-based index would involve finding which objects contain as many of the three trigrams as possible. As a concrete example of using trigram search to search for a regular expression query, consider searching for the string ab[cd]e , where the brackets denote that the third character in the ...
This number is called the edit distance between the string and the pattern. The usual primitive operations are: [1] insertion: cot → coat; deletion: coat → cot; substitution: coat → cost; These three operations may be generalized as forms of substitution by adding a NULL character (here symbolized by *) wherever a character has been ...
The variable z is used to hold the length of the longest common substring found so far. The set ret is used to hold the set of strings which are of length z. The set ret can be saved efficiently by just storing the index i, which is the last character of the longest common substring (of size z) instead of S[(i-z+1)..i].
PostgreSQL supports a binary communication protocol that allows applications to connect to the database server. The protocol is versioned (currently 3.0, as of PostgreSQL 7.4) and has a detailed specification. [47] The official client implementation of this communication protocol is a C API, libpq. [48]
The -character is treated as a literal character if it is the last or the first (after the ^, if present) character within the brackets: [abc-], [-abc], [^-abc]. Backslash escapes are not allowed. The ] character can be included in a bracket expression if it is the first (after the ^, if present) character: []abc], [^]abc]. [^ ]