使用SQLite FTS4进行自动OR查询
我有一个SQLite FTS4数据库，我希望能够通过用户输入对它进行OR查询，例如，如果用户输入“你好那里”，我想做
SELECT * FROM fts_table WHERE text MATCHES 'hello OR there'. 但是，如果我传递简单地传入用户字符串，我会得到一个隐式的AND查询。 我当然可以自己标记字符串，并插入OR，但后来我使用自己的tokenizer，它可能与SQLite的FTS内部使用的tokenizer不同。
有没有办法从我的C包装器访问SQLite标记生成器，或者构建执行此操作的SQL查询，方法如下：
SELECT * FROM fts_table WHERE text MATCHES interpolate('hello there', ' OR ')
谢谢任何指针将不胜感激。
编辑：
这个问题的任何未来读者都应该注意另一个问题： 如何为SQLite FTS查询转义字符串，只是在字符串中插入OR是不安全的，因为你经常会得到无效的字符串，例如，如果用户输入hello AND there插值OR将创建无效的hello OR AND OR there这是无效的。 所以
所以回答我的部分问题：事实certificate你可以通过SELECT fts3_tokenizer(访问指向SQLite tokenizer函数的指针。 有关更多详细信息，请参阅http://www.sqlite.org/fts3.html#section_8_1 。
这将返回一个sqlite3_tokenizer_module结构，其中包含函数指针xCreate ， xOpen和xNext 。
您需要将头文件fts3_tokenizer.h添加到项目中，如此处所述。 http://www.mail-archive.com/sqlite-users%40sqlite.org/msg62644.html
我将sqlite3_tokenizer_module的定义放在下面（逐字复制，因为它包含有用的注释）
/* ** Structures used by the tokenizer interface. When a new tokenizer ** implementation is registered, the caller provides a pointer to ** an sqlite3_tokenizer_module containing pointers to the callback ** functions that make up an implementation. ** ** When an fts3 table is created, it passes any arguments passed to ** the tokenizer clause of the CREATE VIRTUAL TABLE statement to the ** sqlite3_tokenizer_module.xCreate() function of the requested tokenizer ** implementation. The xCreate() function in turn returns an ** sqlite3_tokenizer structure representing the specific tokenizer to ** be used for the fts3 table (customized by the tokenizer clause arguments). ** ** To tokenize an input buffer, the sqlite3_tokenizer_module.xOpen() ** method is called. It returns an sqlite3_tokenizer_cursor object ** that may be used to tokenize a specific input buffer based on ** the tokenization rules supplied by a specific sqlite3_tokenizer ** object. */ typedef struct sqlite3_tokenizer_module sqlite3_tokenizer_module; typedef struct sqlite3_tokenizer sqlite3_tokenizer; typedef struct sqlite3_tokenizer_cursor sqlite3_tokenizer_cursor; struct sqlite3_tokenizer_module { /* ** Structure version. Should always be set to 0 or 1. */ int iVersion; /* ** Create a new tokenizer. The values in the argv[] array are the ** arguments passed to the "tokenizer" clause of the CREATE VIRTUAL ** TABLE statement that created the fts3 table. For example, if ** the following SQL is executed: ** ** CREATE .. USING fts3( ... , tokenizer arg1 arg2) ** ** then argc is set to 2, and the argv[] array contains pointers ** to the strings "arg1" and "arg2". ** ** This method should return either SQLITE_OK (0), or an SQLite error ** code. If SQLITE_OK is returned, then *ppTokenizer should be set ** to point at the newly created tokenizer structure. The generic ** sqlite3_tokenizer.pModule variable should not be initialized by ** this callback. The caller will do so. */ int (*xCreate)( int argc, /* Size of argv array */ const char *const*argv, /* Tokenizer argument strings */ sqlite3_tokenizer **ppTokenizer /* OUT: Created tokenizer */ ); /* ** Destroy an existing tokenizer. The fts3 module calls this method ** exactly once for each successful call to xCreate(). */ int (*xDestroy)(sqlite3_tokenizer *pTokenizer); /* ** Create a tokenizer cursor to tokenize an input buffer. The caller ** is responsible for ensuring that the input buffer remains valid ** until the cursor is closed (using the xClose() method). */ int (*xOpen)( sqlite3_tokenizer *pTokenizer, /* Tokenizer object */ const char *pInput, int nBytes, /* Input buffer */ sqlite3_tokenizer_cursor **ppCursor /* OUT: Created tokenizer cursor */ ); /* ** Destroy an existing tokenizer cursor. The fts3 module calls this ** method exactly once for each successful call to xOpen(). */ int (*xClose)(sqlite3_tokenizer_cursor *pCursor); /* ** Retrieve the next token from the tokenizer cursor pCursor. This ** method should either return SQLITE_OK and set the values of the ** "OUT" variables identified below, or SQLITE_DONE to indicate that ** the end of the buffer has been reached, or an SQLite error code. ** ** *ppToken should be set to point at a buffer containing the ** normalized version of the token (ie after any case-folding and/or ** stemming has been performed). *pnBytes should be set to the length ** of this buffer in bytes. The input text that generated the token is ** identified by the byte offsets returned in *piStartOffset and ** *piEndOffset. *piStartOffset should be set to the index of the first ** byte of the token in the input buffer. *piEndOffset should be set ** to the index of the first byte just past the end of the token in ** the input buffer. ** ** The buffer *ppToken is set to point at is managed by the tokenizer ** implementation. It is only required to be valid until the next call ** to xNext() or xClose(). */ /* TODO(shess) current implementation requires pInput to be ** nul-terminated. This should either be fixed, or pInput/nBytes ** should be converted to zInput. */ int (*xNext)( sqlite3_tokenizer_cursor *pCursor, /* Tokenizer cursor */ const char **ppToken, int *pnBytes, /* OUT: Normalized text for token */ int *piStartOffset, /* OUT: Byte offset of token in input buffer */ int *piEndOffset, /* OUT: Byte offset of end of token in input buffer */ int *piPosition /* OUT: Number of tokens returned before this one */ ); /*********************************************************************** ** Methods below this point are only available if iVersion>=1. */ /* ** Configure the language id of a tokenizer cursor. */ int (*xLanguageid)(sqlite3_tokenizer_cursor *pCsr, int iLangid); };