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| 1 | |
| 2 1. OVERVIEW | |
| 3 | |
| 4 This README file describes the syntax of the arguments that may be passed to | |
| 5 the FTS3 MATCH operator used for full-text queries. For example, if table | |
| 6 "t1" is an Fts3 virtual table, the following SQL query: | |
| 7 | |
| 8 SELECT * FROM t1 WHERE <col> MATCH <full-text query> | |
| 9 | |
| 10 may be used to retrieve all rows that match a specified for full-text query. | |
| 11 The text "<col>" should be replaced by either the name of the fts3 table | |
| 12 (in this case "t1"), or by the name of one of the columns of the fts3 | |
| 13 table. <full-text-query> should be replaced by an SQL expression that | |
| 14 computes to a string containing an Fts3 query. | |
| 15 | |
| 16 If the left-hand-side of the MATCH operator is set to the name of the | |
| 17 fts3 table, then by default the query may be matched against any column | |
| 18 of the table. If it is set to a column name, then by default the query | |
| 19 may only match the specified column. In both cases this may be overriden | |
| 20 as part of the query text (see sections 2 and 3 below). | |
| 21 | |
| 22 As of SQLite version 3.6.8, Fts3 supports two slightly different query | |
| 23 formats; the standard syntax, which is used by default, and the enhanced | |
| 24 query syntax which can be selected by compiling with the pre-processor | |
| 25 symbol SQLITE_ENABLE_FTS3_PARENTHESIS defined. | |
| 26 | |
| 27 -DSQLITE_ENABLE_FTS3_PARENTHESIS | |
| 28 | |
| 29 2. STANDARD QUERY SYNTAX | |
| 30 | |
| 31 When using the standard Fts3 query syntax, a query usually consists of a | |
| 32 list of terms (words) separated by white-space characters. To match a | |
| 33 query, a row (or column) of an Fts3 table must contain each of the specified | |
| 34 terms. For example, the following query: | |
| 35 | |
| 36 <col> MATCH 'hello world' | |
| 37 | |
| 38 matches rows (or columns, if <col> is the name of a column name) that | |
| 39 contain at least one instance of the token "hello", and at least one | |
| 40 instance of the token "world". Tokens may be grouped into phrases using | |
| 41 quotation marks. In this case, a matching row or column must contain each | |
| 42 of the tokens in the phrase in the order specified, with no intervening | |
| 43 tokens. For example, the query: | |
| 44 | |
| 45 <col> MATCH '"hello world" joe" | |
| 46 | |
| 47 matches the first of the following two documents, but not the second or | |
| 48 third: | |
| 49 | |
| 50 "'Hello world', said Joe." | |
| 51 "One should always greet the world with a cheery hello, thought Joe." | |
| 52 "How many hello world programs could their be?" | |
| 53 | |
| 54 As well as grouping tokens together by phrase, the binary NEAR operator | |
| 55 may be used to search for rows that contain two or more specified tokens | |
| 56 or phrases within a specified proximity of each other. The NEAR operator | |
| 57 must always be specified in upper case. The word "near" in lower or mixed | |
| 58 case is treated as an ordinary token. For example, the following query: | |
| 59 | |
| 60 <col> MATCH 'engineering NEAR consultancy' | |
| 61 | |
| 62 matches rows that contain both the "engineering" and "consultancy" tokens | |
| 63 in the same column with not more than 10 other words between them. It does | |
| 64 not matter which of the two terms occurs first in the document, only that | |
| 65 they be seperated by only 10 tokens or less. The user may also specify | |
| 66 a different required proximity by adding "/N" immediately after the NEAR | |
| 67 operator, where N is an integer. For example: | |
| 68 | |
| 69 <col> MATCH 'engineering NEAR/5 consultancy' | |
| 70 | |
| 71 searches for a row containing an instance of each specified token seperated | |
| 72 by not more than 5 other tokens. More than one NEAR operator can be used | |
| 73 in as sequence. For example this query: | |
| 74 | |
| 75 <col> MATCH 'reliable NEAR/2 engineering NEAR/5 consultancy' | |
| 76 | |
| 77 searches for a row that contains an instance of the token "reliable" | |
| 78 seperated by not more than two tokens from an instance of "engineering", | |
| 79 which is in turn separated by not more than 5 other tokens from an | |
| 80 instance of the term "consultancy". Phrases enclosed in quotes may | |
| 81 also be used as arguments to the NEAR operator. | |
| 82 | |
| 83 Similar to the NEAR operator, one or more tokens or phrases may be | |
| 84 separated by OR operators. In this case, only one of the specified tokens | |
| 85 or phrases must appear in the document. For example, the query: | |
| 86 | |
| 87 <col> MATCH 'hello OR world' | |
| 88 | |
| 89 matches rows that contain either the term "hello", or the term "world", | |
| 90 or both. Note that unlike in many programming languages, the OR operator | |
| 91 has a higher precedence than the AND operators implied between white-space | |
| 92 separated tokens. The following query matches documents that contain the | |
| 93 term 'sqlite' and at least one of the terms 'fantastic' or 'impressive', | |
| 94 not those that contain both 'sqlite' and 'fantastic' or 'impressive': | |
| 95 | |
| 96 <col> MATCH 'sqlite fantastic OR impressive' | |
| 97 | |
| 98 Any token that is part of an Fts3 query expression, whether or not it is | |
| 99 part of a phrase enclosed in quotes, may have a '*' character appended to | |
| 100 it. In this case, the token matches all terms that begin with the characters | |
| 101 of the token, not just those that exactly match it. For example, the | |
| 102 following query: | |
| 103 | |
| 104 <col> MATCH 'sql*' | |
| 105 | |
| 106 matches all rows that contain the term "SQLite", as well as those that | |
| 107 contain "SQL". | |
| 108 | |
| 109 A token that is not part of a quoted phrase may be preceded by a '-' | |
| 110 character, which indicates that matching rows must not contain the | |
| 111 specified term. For example, the following: | |
| 112 | |
| 113 <col> MATCH '"database engine" -sqlite' | |
| 114 | |
| 115 matches rows that contain the phrase "database engine" but do not contain | |
| 116 the term "sqlite". If the '-' character occurs inside a quoted phrase, | |
| 117 it is ignored. It is possible to use both the '-' prefix and the '*' postfix | |
| 118 on a single term. At this time, all Fts3 queries must contain at least | |
| 119 one term or phrase that is not preceded by the '-' prefix. | |
| 120 | |
| 121 Regardless of whether or not a table name or column name is used on the | |
| 122 left hand side of the MATCH operator, a specific column of the fts3 table | |
| 123 may be associated with each token in a query by preceding a token with | |
| 124 a column name followed by a ':' character. For example, regardless of what | |
| 125 is specified for <col>, the following query requires that column "col1" | |
| 126 of the table contains the term "hello", and that column "col2" of the | |
| 127 table contains the term "world". If the table does not contain columns | |
| 128 named "col1" and "col2", then an error is returned and the query is | |
| 129 not run. | |
| 130 | |
| 131 <col> MATCH 'col1:hello col2:world' | |
| 132 | |
| 133 It is not possible to associate a specific table column with a quoted | |
| 134 phrase or a term preceded by a '-' operator. A '*' character may be | |
| 135 appended to a term associated with a specific column for prefix matching. | |
| 136 | |
| 137 3. ENHANCED QUERY SYNTAX | |
| 138 | |
| 139 The enhanced query syntax is quite similar to the standard query syntax, | |
| 140 with the following four differences: | |
| 141 | |
| 142 1) Parenthesis are supported. When using the enhanced query syntax, | |
| 143 parenthesis may be used to overcome the built-in precedence of the | |
| 144 supplied binary operators. For example, the following query: | |
| 145 | |
| 146 <col> MATCH '(hello world) OR (simple example)' | |
| 147 | |
| 148 matches documents that contain both "hello" and "world", and documents | |
| 149 that contain both "simple" and "example". It is not possible to forumlate | |
| 150 such a query using the standard syntax. | |
| 151 | |
| 152 2) Instead of separating tokens and phrases by whitespace, an AND operator | |
| 153 may be explicitly specified. This does not change query processing at | |
| 154 all, but may be used to improve readability. For example, the following | |
| 155 query is handled identically to the one above: | |
| 156 | |
| 157 <col> MATCH '(hello AND world) OR (simple AND example)' | |
| 158 | |
| 159 As with the OR and NEAR operators, the AND operator must be specified | |
| 160 in upper case. The word "and" specified in lower or mixed case is | |
| 161 handled as a regular token. | |
| 162 | |
| 163 3) The '-' token prefix is not supported. Instead, a new binary operator, | |
| 164 NOT, is included. The NOT operator requires that the query specified | |
| 165 as its left-hand operator matches, but that the query specified as the | |
| 166 right-hand operator does not. For example, to query for all rows that | |
| 167 contain the term "example" but not the term "simple", the following | |
| 168 query could be used: | |
| 169 | |
| 170 <col> MATCH 'example NOT simple' | |
| 171 | |
| 172 As for all other operators, the NOT operator must be specified in | |
| 173 upper case. Otherwise it will be treated as a regular token. | |
| 174 | |
| 175 4) Unlike in the standard syntax, where the OR operator has a higher | |
| 176 precedence than the implicit AND operator, when using the enhanced | |
| 177 syntax implicit and explict AND operators have a higher precedence | |
| 178 than OR operators. Using the enhanced syntax, the following two | |
| 179 queries are equivalent: | |
| 180 | |
| 181 <col> MATCH 'sqlite fantastic OR impressive' | |
| 182 <col> MATCH '(sqlite AND fantastic) OR impressive' | |
| 183 | |
| 184 however, when using the standard syntax, the query: | |
| 185 | |
| 186 <col> MATCH 'sqlite fantastic OR impressive' | |
| 187 | |
| 188 is equivalent to the enhanced syntax query: | |
| 189 | |
| 190 <col> MATCH 'sqlite AND (fantastic OR impressive)' | |
| 191 | |
| 192 The precedence of all enhanced syntax operators, in order from highest | |
| 193 to lowest, is: | |
| 194 | |
| 195 NEAR (highest precedence, tightest grouping) | |
| 196 NOT | |
| 197 AND | |
| 198 OR (lowest precedence, loosest grouping) | |
| 199 | |
| 200 Using the advanced syntax, it is possible to specify expressions enclosed | |
| 201 in parenthesis as operands to the NOT, AND and OR operators. However both | |
| 202 the left and right hand side operands of NEAR operators must be either | |
| 203 tokens or phrases. Attempting the following query will return an error: | |
| 204 | |
| 205 <col> MATCH 'sqlite NEAR (fantastic OR impressive)' | |
| 206 | |
| 207 Queries of this form must be re-written as: | |
| 208 | |
| 209 <col> MATCH 'sqlite NEAR fantastic OR sqlite NEAR impressive' | |
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Chromium Code Reviews
Issue 2363173002:
[sqlite] Remove obsolete reference version 3.8.7.4. (Closed)
