7.18.9. grn_expr

grn_expr is an grn_obj that represents an expression. Here is a list of what expression can do:

  • Expression can apply some operations to a record by grn_expr_exec().
  • Expression can represents search condition. grn_table_select() can select records that match against the search condition represented by expression.

There are two string representations of expression:

grn_expr_parse() parses string represented expression and appends the parsed expression to another expression.

7.18.9.1. Example

TODO...

7.18.9.2. Reference

GRN_API grn_obj *grn_expr_create(grn_ctx *ctx, const char *name, unsigned int name_size)
GRN_API grn_rc grn_expr_close(grn_ctx *ctx, grn_obj *expr)
GRN_API grn_obj *grn_expr_add_var(grn_ctx *ctx, grn_obj *expr, const char *name, unsigned int name_size)
GRN_API grn_obj *grn_expr_get_var_by_offset(grn_ctx *ctx, grn_obj *expr, unsigned int offset)
GRN_API grn_obj *grn_expr_append_obj(grn_ctx *ctx, grn_obj *expr, grn_obj *obj, grn_operator op, int nargs);
GRN_API grn_obj *grn_expr_append_const(grn_ctx *ctx, grn_obj *expr, grn_obj *obj, grn_operator op, int nargs)
GRN_API grn_obj *grn_expr_append_const_str(grn_ctx *ctx, grn_obj *expr, const char *str, unsigned int str_size, grn_operator op, int nargs)
GRN_API grn_obj *grn_expr_append_const_int(grn_ctx *ctx, grn_obj *expr, int i, grn_operator op, int nargs)
GRN_API grn_rc grn_expr_append_op(grn_ctx *ctx, grn_obj *expr, grn_operator op, int nargs)
grn_rc grn_expr_get_keywords(grn_ctx *ctx, grn_obj *expr, grn_obj *keywords)

Extracts keywords from expr and stores to keywords. Keywords in keywords are owned by expr. Don't unlink them. Each keyword is GRN_BULK and its domain is GRN_DB_TEXT.

keywords must be GRN_PVECTOR.

Here is an example code:

grn_obj keywords;
GRN_PTR_INIT(&keywords, GRN_OBJ_VECTOR, GRN_ID_NIL);
grn_expr_get_keywords(ctx, expr, &keywords);
{
  int i, n_keywords;
  n_keywords = GRN_BULK_VSIZE(&keywords) / sizeof(grn_obj *);
  for (i = 0; i < n_keywords; i++) {
    grn_obj *keyword = GRN_PTR_VALUE_AT(&keywords, i);
    const char *keyword_content;
    int keyword_size;
    keyword_content = GRN_TEXT_VALUE(keyword);
    keyword_size = GRN_TEXT_LEN(keyword);
    /*
      Use keyword_content and keyword_size.
      You don't need to unlink keyword.
      keyword is owned by expr.
    */
  }
}
GRN_OBJ_FIN(ctx, &keywords);
Parameters:
  • ctx -- The context that creates the expr.
  • expr -- The expression to be extracted.
  • keywords --

    The container to store extracted keywords. It must be GRN_PVECTOR.

    Each extracted keyword is GRN_BULK and its domain is GRN_DB_TEXT.

    Extracted keywords are owned by expr. Don't unlink them.
Returns:

GRN_SUCCESS on success, not GRN_SUCCESS on error.
grn_rc grn_expr_syntax_escape(grn_ctx *ctx, const char *string, int string_size, const char *target_characters, char escape_character, grn_obj *escaped_string)

Escapes target_characters in string by escape_character.

Parameters:
  • ctx -- Its encoding must be the same encoding of string. It is used for allocating buffer for escaped_string.
  • string -- String expression representation.
  • string_size -- The byte size of string. -1 means string is NULL terminated string.
  • target_characters -- NULL terminated escape target characters. For example, "+-><~*()\"\\:" is target_characters for Query syntax.
  • escape_character -- The character to use escape a character in target_characters. For example, \\ (backslash) is escaped_character for Query syntax.
  • escaped_string -- The output of escaped string. It should be text typed bulk.
Returns:

GRN_SUCCESS on success, not GRN_SUCCESS on error.
grn_rc grn_expr_syntax_escape_query(grn_ctx *ctx, const char *query, int query_size, grn_obj *escaped_query)

Escapes special characters in Query syntax.

Parameters:
  • ctx -- Its encoding must be the same encoding of query. It is used for allocating buffer for escaped_query.
  • query -- String expression representation in Query syntax.
  • query_size -- The byte size of query. -1 means query is NULL terminated string.
  • escaped_query -- The output of escaped query. It should be text typed bulk.
Returns:

GRN_SUCCESS on success, not GRN_SUCCESS on error.
GRN_API grn_rc grn_expr_compile(grn_ctx *ctx, grn_obj *expr)
GRN_API grn_obj *grn_expr_exec(grn_ctx *ctx, grn_obj *expr, int nargs)
GRN_API grn_obj *grn_expr_alloc(grn_ctx *ctx, grn_obj *expr, grn_id domain, grn_obj_flags flags)