Azure 认知搜索的 OData 表达式语法参考

Azure 认知搜索在整个 API 中使用 OData 表达式作为参数。 最常见的是,OData 表达式用于 $orderby$filter 参数。 这些表达式可能很复杂,包含多个子句、函数和运算符。 但是,甚至简单的 OData 表达式(如属性路径)都在 Azure 认知搜索 REST API 的许多部分中使用。 例如,路径表达式用于引用 API 中各处的复杂字段的子字段,例如在建议器评分函数$select 参数,甚至在 Lucene 查询中的字段搜索中列出子字段时。

本文使用正式语法描述所有这些形式的 OData 表达式。 还有一个交互式图表,以帮助直观地探索语法。

正式语法

我们可以使用 EBNF(扩展巴科斯-瑙尔范式)语法描述 Azure 认知搜索支持的 OData 语言的子集。 规则以“自上而下”的方式列出,从最复杂的表达式开始,并将其分解为更原始的表达式。 顶部是与 Azure 认知搜索 REST API 的特定参数相对应的语法规则:

  • $filter,由 filter_expression 规则定义。
  • $orderby,由 order_by_expression 规则定义。
  • $select,由 select_expression 规则定义。
  • 字段路径,由 field_path 规则定义。 在整个 API 中使用字段路径。 它们可以引用索引的顶级字段,也可以引用具有一个或多个复杂字段上级的子字段。

EBNF 之后是一个可浏览的语法图,可用于交互式地探索语法及其规则之间的关系。

/* Top-level rules */

filter_expression ::= boolean_expression

order_by_expression ::= order_by_clause(',' order_by_clause)*

select_expression ::= '*' | field_path(',' field_path)*

field_path ::= identifier('/'identifier)*

/* Shared base rules */

identifier ::= [a-zA-Z_][a-zA-Z_0-9]*

/* Rules for $orderby */

order_by_clause ::= (field_path | sortable_function) ('asc' | 'desc')?

sortable_function ::= geo_distance_call | 'search.score()'

/* Rules for $filter */

boolean_expression ::=
    collection_filter_expression
    | logical_expression
    | comparison_expression
    | boolean_literal
    | boolean_function_call
    | '(' boolean_expression ')'
    | variable

/* This can be a range variable in the case of a lambda, or a field path. */
variable ::= identifier | field_path

collection_filter_expression ::=
    field_path'/all(' lambda_expression ')'
    | field_path'/any(' lambda_expression ')'
    | field_path'/any()'

lambda_expression ::= identifier ':' boolean_expression

logical_expression ::=
    boolean_expression ('and' | 'or') boolean_expression
    | 'not' boolean_expression

comparison_expression ::= 
    variable_or_function comparison_operator constant | 
    constant comparison_operator variable_or_function

variable_or_function ::= variable | function_call

comparison_operator ::= 'gt' | 'lt' | 'ge' | 'le' | 'eq' | 'ne'

/* Rules for constants and literals */

constant ::=
    string_literal
    | date_time_offset_literal
    | integer_literal
    | float_literal
    | boolean_literal
    | 'null'

string_literal ::= "'"([^'] | "''")*"'"

date_time_offset_literal ::= date_part'T'time_part time_zone

date_part ::= year'-'month'-'day

time_part ::= hour':'minute(':'second('.'fractional_seconds)?)?

zero_to_fifty_nine ::= [0-5]digit

digit ::= [0-9]

year ::= digit digit digit digit

month ::= '0'[1-9] | '1'[0-2]

day ::= '0'[1-9] | [1-2]digit | '3'[0-1]

hour ::= [0-1]digit | '2'[0-3]

minute ::= zero_to_fifty_nine

second ::= zero_to_fifty_nine

fractional_seconds ::= integer_literal

time_zone ::= 'Z' | sign hour':'minute

sign ::= '+' | '-'

/* In practice integer literals are limited in length to the precision of
the corresponding EDM data type. */
integer_literal ::= sign? digit+

float_literal ::=
    sign? whole_part fractional_part? exponent?
    | 'NaN'
    | '-INF'
    | 'INF'

whole_part ::= integer_literal

fractional_part ::= '.'integer_literal

exponent ::= 'e' sign? integer_literal

boolean_literal ::= 'true' | 'false'

/* Rules for functions */

function_call ::=
    geo_distance_call |
    boolean_function_call

geo_distance_call ::=
    'geo.distance(' variable ',' geo_point ')'
    | 'geo.distance(' geo_point ',' variable ')'

geo_point ::= "geography'POINT(" lon_lat ")'"

lon_lat ::= float_literal ' ' float_literal

boolean_function_call ::=
    geo_intersects_call |
    search_in_call |
    search_is_match_call

geo_intersects_call ::=
    'geo.intersects(' variable ',' geo_polygon ')'

/* You need at least four points to form a polygon, where the first and
last points are the same. */
geo_polygon ::=
    "geography'POLYGON((" lon_lat ',' lon_lat ',' lon_lat ',' lon_lat_list "))'"

lon_lat_list ::= lon_lat(',' lon_lat)*

search_in_call ::=
    'search.in(' variable ',' string_literal(',' string_literal)? ')'

/* Note that it is illegal to call search.ismatch or search.ismatchscoring
from inside a lambda expression. */
search_is_match_call ::=
    'search.ismatch'('scoring')?'(' search_is_match_parameters ')'

search_is_match_parameters ::=
    string_literal(',' string_literal(',' query_type ',' search_mode)?)?

query_type ::= "'full'" | "'simple'"

search_mode ::= "'any'" | "'all'"

语法图

若要直观地探索 Azure 认知搜索支持的 OData 语言语法,请尝试交互式语法图:

另请参阅