7.25.11. 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.
7.25.11.1. Example¶
TODO…
7.25.11.2. Reference¶
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GRN_API grn_obj *
grn_expr_add_var(grn_ctx *ctx, grn_obj *expr, const char *name, unsigned int name_size)¶
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GRN_API grn_obj *grn_expr_append_obj(grn_ctx *ctx, grn_obj *expr, grn_obj *obj, grn_operator op, int nargs);
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GRN_API grn_obj *
grn_expr_append_const(grn_ctx *ctx, grn_obj *expr, grn_obj *obj, grn_operator op, int nargs)¶
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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)¶
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GRN_API grn_obj *
grn_expr_append_const_int(grn_ctx *ctx, grn_obj *expr, int i, grn_operator op, int nargs)¶
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grn_rc
grn_expr_get_keywords(grn_ctx *ctx, grn_obj *expr, grn_obj *keywords)¶ Extracts keywords from
exprand stores tokeywords. Keywords inkeywordsare owned byexpr. Don’t unlink them. Each keyword isGRN_BULKand its domain isGRN_DB_TEXT.keywordsmust beGRN_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_BULKand its domain isGRN_DB_TEXT.Extracted keywords are owned by
expr. Don’t unlink them.
- Returns
GRN_SUCCESSon success, notGRN_SUCCESSon error.
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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_charactersinstringbyescape_character.- Parameters
ctx – Its encoding must be the same encoding of
string. It is used for allocating buffer forescaped_string.string – String expression representation.
string_size – The byte size of
string.-1meansstringis NULL terminated string.target_characters – NULL terminated escape target characters. For example,
"+-><~*()\"\\:"istarget_charactersfor Query syntax.escape_character – The character to use escape a character in
target_characters. For example,\\(backslash) isescaped_characterfor Query syntax.escaped_string – The output of escaped
string. It should be text typed bulk.
- Returns
GRN_SUCCESSon success, notGRN_SUCCESSon error.
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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 forescaped_query.query – String expression representation in Query syntax.
query_size – The byte size of
query.-1meansqueryis NULL terminated string.escaped_query – The output of escaped
query. It should be text typed bulk.
- Returns
GRN_SUCCESSon success, notGRN_SUCCESSon error.