如何为Postgresql数据库全文搜索(full text search)编写解析器(parser)

#include "postgres.h"

#include "utils/builtins.h"

#ifdef PG_MODULE_MAGIC

PG_MODULE_MAGIC;

#endif

/*

* types

*/

/* self-defined type */

typedef struct {

char * buffer; /* text to parse */

int len; /* length of the text in buffer */

int pos; /* position of the parser */

} ParserState;

/* copy-paste from wparser.h of tsearch2 */

typedef struct {

int lexid;

char *alias;

char *descr;

} LexDescr;

/*

* prototypes

*/

PG_FUNCTION_INFO_V1(testprs_start);

Datum testprs_start(PG_FUNCTION_ARGS);

PG_FUNCTION_INFO_V1(testprs_getlexeme);

Datum testprs_getlexeme(PG_FUNCTION_ARGS);

PG_FUNCTION_INFO_V1(testprs_end);

Datum testprs_end(PG_FUNCTION_ARGS);

PG_FUNCTION_INFO_V1(testprs_lextype);

Datum testprs_lextype(PG_FUNCTION_ARGS);

/*

* functions

*/

Datum testprs_start

(PG_FUNCTION_ARGS)

{

ParserState *pst = (ParserState *) palloc(sizeof(ParserState));

pst->buffer = (char *) PG_GETARG_POINTER(0);

pst->len = PG_GETARG_INT32(1);

pst->pos = 0;

PG_RETURN_POINTER(pst);

}

Datum testprs_getlexeme

(PG_FUNCTION_ARGS)

{

ParserState *pst = (ParserState *) PG_GETARG_POINTER(0);

char **t = (char **) PG_GETARG_POINTER(1);

int *tlen = (int *) PG_GETARG_POINTER(2);

int type;

*tlen = pst->pos;

*t = pst->buffer + pst->pos;

HTML clipboard/* main process here */

  if (((pst->buffer)[pst->pos] >= 'A' && (pst->buffer)[pst->pos] <= 'Z') && 
(pst->pos < pst->len)) {

 /* word type */

 type = 3;

 (pst->pos)++;

 /* for case like: ItemURL => Item URL*/

 if(((pst->buffer)[pst->pos] >= 'A' && (pst->buffer)[pst->pos] <= 'Z') && (pst->pos 
< pst->len)){

 while (((pst->buffer)[pst->pos] >= 'A' && (pst->buffer)[pst->pos] <= 'Z') 
&& (pst->pos < pst->len)) {

 (pst->pos)++;

 }

 }

 

 /* go to the next upper case character */

 while (((pst->buffer)[pst->pos] >= 'a' && (pst->buffer)[pst->pos] <= 'z') 
&& (pst->pos < pst->len)) {

 (pst->pos)++;

 }

 } 

 

 if (((pst->buffer)[pst->pos] >= 'a' && (pst->buffer)[pst->pos] <= 'z') && 
(pst->pos < pst->len)) {

 /* word type */

 type = 3;

 (pst->pos)++;

 /* go to the next upper case character */

 while (((pst->buffer)[pst->pos] >= 'a' && (pst->buffer)[pst->pos] <= 'z') 
&& (pst->pos < pst->len)) {

 (pst->pos)++;

 }

 }

*tlen = pst->pos - *tlen;

/* we are finished if (*tlen == 0) */

if (*tlen == 0) type=0;

PG_RETURN_INT32(type);

}

Datum testprs_end

(PG_FUNCTION_ARGS)

{

ParserState *pst = (ParserState *) PG_GETARG_POINTER(0);

pfree(pst);

PG_RETURN_VOID();

}

Datum testprs_lextype

(PG_FUNCTION_ARGS)

{

/*

Remarks:

- we have to return the blanks for headline reason

- we use the same lexids like Teodor in the default

word parser; in this way we can reuse the headline

function of the default word parser.

*/

LexDescr *descr = (LexDescr *) palloc(sizeof(LexDescr) * (2+1));

/* there are only two types in this parser */

descr[0].lexid = 3;

descr[0].alias = pstrdup("word");

descr[0].descr = pstrdup("Word");

descr[1].lexid = 12;

descr[1].alias = pstrdup("blank");

descr[1].descr = pstrdup("Space symbols");

descr[2].lexid = 0;

PG_RETURN_POINTER(descr);

}