mirror of https://gitee.com/bigwinds/arangodb
Documentation: Aql update
This commit is contained in:
jmvan
parent
7a11220acc
commit
adc5702422
|
|
@ -1,6 +1,5 @@
|
|||
!CHAPTER Advanced features
|
||||
|
||||
|
||||
* [Combining queries](CombiningQueries.md)
|
||||
* [Array operators](ArrayOperators.md)
|
||||
|
||||
|
|
|
|||
|
|
@ -0,0 +1,236 @@
|
|||
!CHAPTER Executing queries from Arangosh
|
||||
|
||||
Within the ArangoDB shell, the *_query* and *_createStatement* methods of the *db* object can be used to execute AQL queries.
|
||||
This chapter also describes how to use data binding, counting, statistics and cursors.
|
||||
|
||||
!SUBSECTION with db._query
|
||||
|
||||
One can execute queries with the *_query* method of the *db* object.
|
||||
This will run the specified query in the context of the currently
|
||||
selected database and return the query results in a cursor. The results of the cursor
|
||||
can be printed using its *toArray* method:
|
||||
|
||||
@startDocuBlockInline 01_workWithAQL_all
|
||||
@EXAMPLE_ARANGOSH_OUTPUT{01_workWithAQL_all}
|
||||
~addIgnoreCollection("mycollection")
|
||||
db._create("mycollection")
|
||||
db.mycollection.save({ _key: "testKey", Hello : "World" })
|
||||
db._query('FOR my IN mycollection RETURN my._key').toArray()
|
||||
@END_EXAMPLE_ARANGOSH_OUTPUT
|
||||
@endDocuBlock 01_workWithAQL_all
|
||||
|
||||
!SUBSUBSECTION db._query Bind parameters
|
||||
|
||||
To pass bind parameters into a query, they can be specified as second argument to the
|
||||
*_query* method:
|
||||
|
||||
@startDocuBlockInline 02_workWithAQL_bindValues
|
||||
@EXAMPLE_ARANGOSH_OUTPUT{02_workWithAQL_bindValues}
|
||||
|db._query(
|
||||
| 'FOR c IN @@collection FILTER c._key == @key RETURN c._key', {
|
||||
| '@collection': 'mycollection',
|
||||
| 'key': 'testKey'
|
||||
}).toArray();
|
||||
@END_EXAMPLE_ARANGOSH_OUTPUT
|
||||
@endDocuBlock 02_workWithAQL_bindValues
|
||||
|
||||
!SUBSUBSECTION ES6 template strings
|
||||
|
||||
It is also possible to use ES6 template strings for generating AQL queries. There is
|
||||
a template string generator function named *aqlQuery*:
|
||||
|
||||
@startDocuBlockInline 02_workWithAQL_aqlQuery
|
||||
@EXAMPLE_ARANGOSH_OUTPUT{02_workWithAQL_aqlQuery}
|
||||
var key = 'testKey';
|
||||
|db._query(
|
||||
| aqlQuery`FOR c IN mycollection FILTER c._key == ${key} RETURN c._key`
|
||||
).toArray();
|
||||
@END_EXAMPLE_ARANGOSH_OUTPUT
|
||||
@endDocuBlock 02_workWithAQL_aqlQuery
|
||||
|
||||
Arbitrary JavaScript expressions can be used in queries that are generated with the
|
||||
*aqlQuery* template string generator. Collection objects are handled automatically:
|
||||
|
||||
@startDocuBlockInline 02_workWithAQL_aqlCollectionQuery
|
||||
@EXAMPLE_ARANGOSH_OUTPUT{02_workWithAQL_aqlCollectionQuery}
|
||||
var key = 'testKey';
|
||||
|db._query(aqlQuery`FOR doc IN ${ db.mycollection } RETURN doc`
|
||||
).toArray();
|
||||
@END_EXAMPLE_ARANGOSH_OUTPUT
|
||||
@endDocuBlock 02_workWithAQL_aqlCollectionQuery
|
||||
|
||||
Note: data-modification AQL queries normally do not return a result (unless the AQL query
|
||||
contains an extra *RETURN* statement). When not using a *RETURN* statement in the query, the
|
||||
*toArray* method will return an empty array.
|
||||
|
||||
!SUBSUBSECTION Statistics and extra Information
|
||||
|
||||
It is always possible to retrieve statistics for a query with the *getExtra* method:
|
||||
|
||||
@startDocuBlockInline 03_workWithAQL_getExtra
|
||||
@EXAMPLE_ARANGOSH_OUTPUT{03_workWithAQL_getExtra}
|
||||
|db._query(`FOR i IN 1..100
|
||||
| INSERT { _key: CONCAT('test', TO_STRING(i)) }
|
||||
| INTO mycollection`
|
||||
).getExtra();
|
||||
@END_EXAMPLE_ARANGOSH_OUTPUT
|
||||
@endDocuBlock 03_workWithAQL_getExtra
|
||||
|
||||
The meaning of the statistics values is described in [Execution statistics](QueryStatistics.md).
|
||||
You also will find warnings in here; If you're designing queries on the shell be sure to also look at it.
|
||||
|
||||
!SUBSECTION with _createStatement (ArangoStatement)
|
||||
|
||||
The *_query* method is a shorthand for creating an ArangoStatement object,
|
||||
executing it and iterating over the resulting cursor. If more control over the
|
||||
result set iteration is needed, it is recommended to first create an
|
||||
ArangoStatement object as follows:
|
||||
|
||||
@startDocuBlockInline 04_workWithAQL_statements1
|
||||
@EXAMPLE_ARANGOSH_OUTPUT{04_workWithAQL_statements1}
|
||||
|stmt = db._createStatement( {
|
||||
"query": "FOR i IN [ 1, 2 ] RETURN i * 2" } );
|
||||
@END_EXAMPLE_ARANGOSH_OUTPUT
|
||||
@endDocuBlock 04_workWithAQL_statements1
|
||||
|
||||
To execute the query, use the *execute* method of the statement:
|
||||
|
||||
@startDocuBlockInline 05_workWithAQL_statements2
|
||||
@EXAMPLE_ARANGOSH_OUTPUT{05_workWithAQL_statements2}
|
||||
~var stmt = db._createStatement( { "query": "FOR i IN [ 1, 2 ] RETURN i * 2" } );
|
||||
c = stmt.execute();
|
||||
@END_EXAMPLE_ARANGOSH_OUTPUT
|
||||
@endDocuBlock 05_workWithAQL_statements2
|
||||
|
||||
!SUBSUBSECTION Cursors
|
||||
|
||||
Once the query executed the query results are available in a cursor.
|
||||
The cursor can return all its results at once using the *toArray* method.
|
||||
This is a short-cut that you can use if you want to access the full result
|
||||
set without iterating over it yourself.
|
||||
|
||||
@startDocuBlockInline 05_workWithAQL_statements3
|
||||
@EXAMPLE_ARANGOSH_OUTPUT{05_workWithAQL_statements3}
|
||||
~var stmt = db._createStatement( { "query": "FOR i IN [ 1, 2 ] RETURN i * 2" } );
|
||||
~var c = stmt.execute();
|
||||
c.toArray();
|
||||
@END_EXAMPLE_ARANGOSH_OUTPUT
|
||||
@endDocuBlock 05_workWithAQL_statements3
|
||||
|
||||
|
||||
|
||||
Cursors can also be used to iterate over the result set document-by-document.
|
||||
To do so, use the *hasNext* and *next* methods of the cursor:
|
||||
|
||||
@startDocuBlockInline 05_workWithAQL_statements4
|
||||
@EXAMPLE_ARANGOSH_OUTPUT{05_workWithAQL_statements4}
|
||||
~var stmt = db._createStatement( { "query": "FOR i IN [ 1, 2 ] RETURN i * 2" } );
|
||||
~var c = stmt.execute();
|
||||
while (c.hasNext()) { require("internal").print(c.next()); }
|
||||
@END_EXAMPLE_ARANGOSH_OUTPUT
|
||||
@endDocuBlock 05_workWithAQL_statements4
|
||||
|
||||
Please note that you can iterate over the results of a cursor only once, and that
|
||||
the cursor will be empty when you have fully iterated over it. To iterate over
|
||||
the results again, the query needs to be re-executed.
|
||||
|
||||
Additionally, the iteration can be done in a forward-only fashion. There is no
|
||||
backwards iteration or random access to elements in a cursor.
|
||||
|
||||
!SUBSUBSECTION ArangoStatement parameters binding
|
||||
|
||||
To execute an AQL query using bind parameters, you need to create a statement first
|
||||
and then bind the parameters to it before execution:
|
||||
|
||||
@startDocuBlockInline 05_workWithAQL_statements5
|
||||
@EXAMPLE_ARANGOSH_OUTPUT{05_workWithAQL_statements5}
|
||||
|var stmt = db._createStatement( {
|
||||
"query": "FOR i IN [ @one, @two ] RETURN i * 2" } );
|
||||
stmt.bind("one", 1);
|
||||
stmt.bind("two", 2);
|
||||
c = stmt.execute();
|
||||
@END_EXAMPLE_ARANGOSH_OUTPUT
|
||||
@endDocuBlock 05_workWithAQL_statements5
|
||||
|
||||
The cursor results can then be dumped or iterated over as usual, e.g.:
|
||||
|
||||
@startDocuBlockInline 05_workWithAQL_statements6
|
||||
@EXAMPLE_ARANGOSH_OUTPUT{05_workWithAQL_statements6}
|
||||
~var stmt = db._createStatement( { "query": "FOR i IN [ @one, @two ] RETURN i * 2" } );
|
||||
~stmt.bind("one", 1);
|
||||
~stmt.bind("two", 2);
|
||||
~var c = stmt.execute();
|
||||
c.toArray();
|
||||
@END_EXAMPLE_ARANGOSH_OUTPUT
|
||||
@endDocuBlock 05_workWithAQL_statements6
|
||||
|
||||
or
|
||||
|
||||
@startDocuBlockInline 05_workWithAQL_statements7
|
||||
@EXAMPLE_ARANGOSH_OUTPUT{05_workWithAQL_statements7}
|
||||
~var stmt = db._createStatement( { "query": "FOR i IN [ @one, @two ] RETURN i * 2" } );
|
||||
~stmt.bind("one", 1);
|
||||
~stmt.bind("two", 2);
|
||||
~var c = stmt.execute();
|
||||
while (c.hasNext()) { require("internal").print(c.next()); }
|
||||
@END_EXAMPLE_ARANGOSH_OUTPUT
|
||||
@endDocuBlock 05_workWithAQL_statements7
|
||||
|
||||
Please note that bind parameters can also be passed into the *_createStatement* method directly,
|
||||
making it a bit more convenient:
|
||||
|
||||
@startDocuBlockInline 05_workWithAQL_statements8
|
||||
@EXAMPLE_ARANGOSH_OUTPUT{05_workWithAQL_statements8}
|
||||
|stmt = db._createStatement( {
|
||||
| "query": "FOR i IN [ @one, @two ] RETURN i * 2",
|
||||
| "bindVars": {
|
||||
| "one": 1,
|
||||
| "two": 2
|
||||
| }
|
||||
} );
|
||||
@END_EXAMPLE_ARANGOSH_OUTPUT
|
||||
@endDocuBlock 05_workWithAQL_statements8
|
||||
|
||||
!SUBSUBSECTION Counting with a cursor
|
||||
|
||||
Cursors also optionally provide the total number of results. By default, they do not.
|
||||
To make the server return the total number of results, you may set the *count* attribute to
|
||||
*true* when creating a statement:
|
||||
|
||||
@startDocuBlockInline 05_workWithAQL_statements9
|
||||
@EXAMPLE_ARANGOSH_OUTPUT{05_workWithAQL_statements9}
|
||||
|stmt = db._createStatement( {
|
||||
| "query": "FOR i IN [ 1, 2, 3, 4 ] RETURN i",
|
||||
"count": true } );
|
||||
@END_EXAMPLE_ARANGOSH_OUTPUT
|
||||
@endDocuBlock 05_workWithAQL_statements9
|
||||
|
||||
After executing this query, you can use the *count* method of the cursor to get the
|
||||
number of total results from the result set:
|
||||
|
||||
@startDocuBlockInline 05_workWithAQL_statements10
|
||||
@EXAMPLE_ARANGOSH_OUTPUT{05_workWithAQL_statements10}
|
||||
~var stmt = db._createStatement( { "query": "FOR i IN [ 1, 2, 3, 4 ] RETURN i", "count": true } );
|
||||
var c = stmt.execute();
|
||||
c.count();
|
||||
@END_EXAMPLE_ARANGOSH_OUTPUT
|
||||
@endDocuBlock 05_workWithAQL_statements10
|
||||
|
||||
Please note that the *count* method returns nothing if you did not specify the *count*
|
||||
attribute when creating the query.
|
||||
|
||||
This is intentional so that the server may apply optimizations when executing the query and
|
||||
construct the result set incrementally. Incremental creation of the result sets
|
||||
is no possible
|
||||
if all of the results need to be shipped to the client anyway. Therefore, the client
|
||||
has the choice to specify *count* and retrieve the total number of results for a query (and
|
||||
disable potential incremental result set creation on the server), or to not retrieve the total
|
||||
number of results and allow the server to apply optimizations.
|
||||
|
||||
Please note that at the moment the server will always create the full result set for each query so
|
||||
specifying or omitting the *count* attribute currently does not have any impact on query execution.
|
||||
This may change in the future. Future versions of ArangoDB may create result sets incrementally
|
||||
on the server-side and may be able to apply optimizations if a result set is not fully fetched by
|
||||
a client.
|
||||
|
||||
|
||||
|
|
@ -3,239 +3,10 @@
|
|||
You can run AQL queries from your application via the HTTP REST API. The full
|
||||
API description is available at [HTTP Interface for AQL Query Cursors](../HttpAqlQueryCursor/README.md).
|
||||
|
||||
You can also run AQL queries from arangosh.
|
||||
The [ArangoDB Web Interface](../WebInterface/README.md) has a specific tab for AQL queries execution.
|
||||
|
||||
!SECTION Executing queries from Arangosh
|
||||
You can run [AQL queries from the ArangoDB Shell](AqlWithArangosh.md) with the *_query* and *_createStatement* methods of the *db* object.
|
||||
This chapter also describes how to use data binding, statistics, counting and cursors with arangosh.
|
||||
|
||||
|
||||
!SUBSECTION with db._query
|
||||
|
||||
One can execute queries with the *_query* method of the *db* object.
|
||||
This will run the specified query in the context of the currently
|
||||
selected database and return the query results in a cursor. The results of the cursor
|
||||
can be printed using its *toArray* method:
|
||||
|
||||
@startDocuBlockInline 01_workWithAQL_all
|
||||
@EXAMPLE_ARANGOSH_OUTPUT{01_workWithAQL_all}
|
||||
~addIgnoreCollection("mycollection")
|
||||
db._create("mycollection")
|
||||
db.mycollection.save({ _key: "testKey", Hello : "World" })
|
||||
db._query('FOR my IN mycollection RETURN my._key').toArray()
|
||||
@END_EXAMPLE_ARANGOSH_OUTPUT
|
||||
@endDocuBlock 01_workWithAQL_all
|
||||
|
||||
!SUBSUBSECTION db._query Bind parameters
|
||||
|
||||
To pass bind parameters into a query, they can be specified as second argument to the
|
||||
*_query* method:
|
||||
|
||||
@startDocuBlockInline 02_workWithAQL_bindValues
|
||||
@EXAMPLE_ARANGOSH_OUTPUT{02_workWithAQL_bindValues}
|
||||
|db._query(
|
||||
| 'FOR c IN @@collection FILTER c._key == @key RETURN c._key', {
|
||||
| '@collection': 'mycollection',
|
||||
| 'key': 'testKey'
|
||||
}).toArray();
|
||||
@END_EXAMPLE_ARANGOSH_OUTPUT
|
||||
@endDocuBlock 02_workWithAQL_bindValues
|
||||
|
||||
!SUBSUBSECTION ES6 template strings
|
||||
|
||||
It is also possible to use ES6 template strings for generating AQL queries. There is
|
||||
a template string generator function named *aqlQuery*:
|
||||
|
||||
@startDocuBlockInline 02_workWithAQL_aqlQuery
|
||||
@EXAMPLE_ARANGOSH_OUTPUT{02_workWithAQL_aqlQuery}
|
||||
var key = 'testKey';
|
||||
|db._query(
|
||||
| aqlQuery`FOR c IN mycollection FILTER c._key == ${key} RETURN c._key`
|
||||
).toArray();
|
||||
@END_EXAMPLE_ARANGOSH_OUTPUT
|
||||
@endDocuBlock 02_workWithAQL_aqlQuery
|
||||
|
||||
Arbitrary JavaScript expressions can be used in queries that are generated with the
|
||||
*aqlQuery* template string generator. Collection objects are handled automatically:
|
||||
|
||||
@startDocuBlockInline 02_workWithAQL_aqlCollectionQuery
|
||||
@EXAMPLE_ARANGOSH_OUTPUT{02_workWithAQL_aqlCollectionQuery}
|
||||
var key = 'testKey';
|
||||
|db._query(aqlQuery`FOR doc IN ${ db.mycollection } RETURN doc`
|
||||
).toArray();
|
||||
@END_EXAMPLE_ARANGOSH_OUTPUT
|
||||
@endDocuBlock 02_workWithAQL_aqlCollectionQuery
|
||||
|
||||
Note: data-modification AQL queries normally do not return a result (unless the AQL query
|
||||
contains an extra *RETURN* statement). When not using a *RETURN* statement in the query, the
|
||||
*toArray* method will return an empty array.
|
||||
|
||||
!SUBSUBSECTION Statistics and extra Information
|
||||
|
||||
It is always possible to retrieve statistics for a query with the *getExtra* method:
|
||||
|
||||
@startDocuBlockInline 03_workWithAQL_getExtra
|
||||
@EXAMPLE_ARANGOSH_OUTPUT{03_workWithAQL_getExtra}
|
||||
|db._query(`FOR i IN 1..100
|
||||
| INSERT { _key: CONCAT('test', TO_STRING(i)) }
|
||||
| INTO mycollection`
|
||||
).getExtra();
|
||||
@END_EXAMPLE_ARANGOSH_OUTPUT
|
||||
@endDocuBlock 03_workWithAQL_getExtra
|
||||
|
||||
The meaning of the statistics values is described in [Execution statistics](QueryStatistics.md).
|
||||
You also will find warnings in here; If you're designing queries on the shell be shure to also look at it.
|
||||
|
||||
!SUBSECTION with _createStatement (ArangoStatement)
|
||||
|
||||
The *_query* method is a shorthand for creating an ArangoStatement object,
|
||||
executing it and iterating over the resulting cursor. If more control over the
|
||||
result set iteration is needed, it is recommended to first create an
|
||||
ArangoStatement object as follows:
|
||||
|
||||
@startDocuBlockInline 04_workWithAQL_statements1
|
||||
@EXAMPLE_ARANGOSH_OUTPUT{04_workWithAQL_statements1}
|
||||
|stmt = db._createStatement( {
|
||||
"query": "FOR i IN [ 1, 2 ] RETURN i * 2" } );
|
||||
@END_EXAMPLE_ARANGOSH_OUTPUT
|
||||
@endDocuBlock 04_workWithAQL_statements1
|
||||
|
||||
To execute the query, use the *execute* method of the statement:
|
||||
|
||||
@startDocuBlockInline 05_workWithAQL_statements2
|
||||
@EXAMPLE_ARANGOSH_OUTPUT{05_workWithAQL_statements2}
|
||||
~var stmt = db._createStatement( { "query": "FOR i IN [ 1, 2 ] RETURN i * 2" } );
|
||||
c = stmt.execute();
|
||||
@END_EXAMPLE_ARANGOSH_OUTPUT
|
||||
@endDocuBlock 05_workWithAQL_statements2
|
||||
|
||||
!SUBSUBSECTION Cursors
|
||||
|
||||
Once the query executed the query results are available in a cursor.
|
||||
The cursor can return all its results at once using the *toArray* method.
|
||||
This is a short-cut that you can use if you want to access the full result
|
||||
set without iterating over it yourself.
|
||||
|
||||
@startDocuBlockInline 05_workWithAQL_statements3
|
||||
@EXAMPLE_ARANGOSH_OUTPUT{05_workWithAQL_statements3}
|
||||
~var stmt = db._createStatement( { "query": "FOR i IN [ 1, 2 ] RETURN i * 2" } );
|
||||
~var c = stmt.execute();
|
||||
c.toArray();
|
||||
@END_EXAMPLE_ARANGOSH_OUTPUT
|
||||
@endDocuBlock 05_workWithAQL_statements3
|
||||
|
||||
|
||||
|
||||
Cursors can also be used to iterate over the result set document-by-document.
|
||||
To do so, use the *hasNext* and *next* methods of the cursor:
|
||||
|
||||
@startDocuBlockInline 05_workWithAQL_statements4
|
||||
@EXAMPLE_ARANGOSH_OUTPUT{05_workWithAQL_statements4}
|
||||
~var stmt = db._createStatement( { "query": "FOR i IN [ 1, 2 ] RETURN i * 2" } );
|
||||
~var c = stmt.execute();
|
||||
while (c.hasNext()) { require("internal").print(c.next()); }
|
||||
@END_EXAMPLE_ARANGOSH_OUTPUT
|
||||
@endDocuBlock 05_workWithAQL_statements4
|
||||
|
||||
Please note that you can iterate over the results of a cursor only once, and that
|
||||
the cursor will be empty when you have fully iterated over it. To iterate over
|
||||
the results again, the query needs to be re-executed.
|
||||
|
||||
Additionally, the iteration can be done in a forward-only fashion. There is no
|
||||
backwards iteration or random access to elements in a cursor.
|
||||
|
||||
!SUBSUBSECTION ArangoStatement parameters binding
|
||||
|
||||
To execute an AQL query using bind parameters, you need to create a statement first
|
||||
and then bind the parameters to it before execution:
|
||||
|
||||
@startDocuBlockInline 05_workWithAQL_statements5
|
||||
@EXAMPLE_ARANGOSH_OUTPUT{05_workWithAQL_statements5}
|
||||
|var stmt = db._createStatement( {
|
||||
"query": "FOR i IN [ @one, @two ] RETURN i * 2" } );
|
||||
stmt.bind("one", 1);
|
||||
stmt.bind("two", 2);
|
||||
c = stmt.execute();
|
||||
@END_EXAMPLE_ARANGOSH_OUTPUT
|
||||
@endDocuBlock 05_workWithAQL_statements5
|
||||
|
||||
The cursor results can then be dumped or iterated over as usual, e.g.:
|
||||
|
||||
@startDocuBlockInline 05_workWithAQL_statements6
|
||||
@EXAMPLE_ARANGOSH_OUTPUT{05_workWithAQL_statements6}
|
||||
~var stmt = db._createStatement( { "query": "FOR i IN [ @one, @two ] RETURN i * 2" } );
|
||||
~stmt.bind("one", 1);
|
||||
~stmt.bind("two", 2);
|
||||
~var c = stmt.execute();
|
||||
c.toArray();
|
||||
@END_EXAMPLE_ARANGOSH_OUTPUT
|
||||
@endDocuBlock 05_workWithAQL_statements6
|
||||
|
||||
or
|
||||
|
||||
@startDocuBlockInline 05_workWithAQL_statements7
|
||||
@EXAMPLE_ARANGOSH_OUTPUT{05_workWithAQL_statements7}
|
||||
~var stmt = db._createStatement( { "query": "FOR i IN [ @one, @two ] RETURN i * 2" } );
|
||||
~stmt.bind("one", 1);
|
||||
~stmt.bind("two", 2);
|
||||
~var c = stmt.execute();
|
||||
while (c.hasNext()) { require("internal").print(c.next()); }
|
||||
@END_EXAMPLE_ARANGOSH_OUTPUT
|
||||
@endDocuBlock 05_workWithAQL_statements7
|
||||
|
||||
Please note that bind parameters can also be passed into the *_createStatement* method directly,
|
||||
making it a bit more convenient:
|
||||
|
||||
@startDocuBlockInline 05_workWithAQL_statements8
|
||||
@EXAMPLE_ARANGOSH_OUTPUT{05_workWithAQL_statements8}
|
||||
|stmt = db._createStatement( {
|
||||
| "query": "FOR i IN [ @one, @two ] RETURN i * 2",
|
||||
| "bindVars": {
|
||||
| "one": 1,
|
||||
| "two": 2
|
||||
| }
|
||||
} );
|
||||
@END_EXAMPLE_ARANGOSH_OUTPUT
|
||||
@endDocuBlock 05_workWithAQL_statements8
|
||||
|
||||
!SUBSUBSECTION Counting with a cursor
|
||||
|
||||
Cursors also optionally provide the total number of results. By default, they do not.
|
||||
To make the server return the total number of results, you may set the *count* attribute to
|
||||
*true* when creating a statement:
|
||||
|
||||
@startDocuBlockInline 05_workWithAQL_statements9
|
||||
@EXAMPLE_ARANGOSH_OUTPUT{05_workWithAQL_statements9}
|
||||
|stmt = db._createStatement( {
|
||||
| "query": "FOR i IN [ 1, 2, 3, 4 ] RETURN i",
|
||||
"count": true } );
|
||||
@END_EXAMPLE_ARANGOSH_OUTPUT
|
||||
@endDocuBlock 05_workWithAQL_statements9
|
||||
|
||||
After executing this query, you can use the *count* method of the cursor to get the
|
||||
number of total results from the result set:
|
||||
|
||||
@startDocuBlockInline 05_workWithAQL_statements10
|
||||
@EXAMPLE_ARANGOSH_OUTPUT{05_workWithAQL_statements10}
|
||||
~var stmt = db._createStatement( { "query": "FOR i IN [ 1, 2, 3, 4 ] RETURN i", "count": true } );
|
||||
var c = stmt.execute();
|
||||
c.count();
|
||||
@END_EXAMPLE_ARANGOSH_OUTPUT
|
||||
@endDocuBlock 05_workWithAQL_statements10
|
||||
|
||||
Please note that the *count* method returns nothing if you did not specify the *count*
|
||||
attribute when creating the query.
|
||||
|
||||
This is intentional so that the server may apply optimizations when executing the query and
|
||||
construct the result set incrementally. Incremental creation of the result sets
|
||||
is no possible
|
||||
if all of the results need to be shipped to the client anyway. Therefore, the client
|
||||
has the choice to specify *count* and retrieve the total number of results for a query (and
|
||||
disable potential incremental result set creation on the server), or to not retrieve the total
|
||||
number of results and allow the server to apply optimizations.
|
||||
|
||||
Please note that at the moment the server will always create the full result set for each query so
|
||||
specifying or omitting the *count* attribute currently does not have any impact on query execution.
|
||||
This may change in the future. Future versions of ArangoDB may create result sets incrementally
|
||||
on the server-side and may be able to apply optimizations if a result set is not fully fetched by
|
||||
a client.
|
||||
|
||||
|
||||
|
|
|
|||
|
|
@ -21,7 +21,7 @@ about the optimizer's view of the query.
|
|||
!SUBSECTION Inspecting plans using the explain helper
|
||||
|
||||
The `explain` method of `ArangoStatement` as shown in the next chapters creates very verbose output.
|
||||
You can work on the output programaticaly, or use this handsome tool that we created
|
||||
You can work on the output programmatically, or use this handsome tool that we created
|
||||
to generate a more human readable representation.
|
||||
|
||||
You may use it like this: (we disable syntax highlighting here)
|
||||
|
|
@ -40,7 +40,7 @@ You may use it like this: (we disable syntax highlighting here)
|
|||
|
||||
!SUBSECTION Execution plans in detail
|
||||
|
||||
Lets have a look at the raw json output of the same execution plan
|
||||
Let's have a look at the raw json output of the same execution plan
|
||||
using the `explain` method of `ArangoStatement`:
|
||||
|
||||
@startDocuBlockInline AQLEXP_01_explainCreate
|
||||
|
|
@ -50,7 +50,7 @@ using the `explain` method of `ArangoStatement`:
|
|||
@END_EXAMPLE_ARANGOSH_OUTPUT
|
||||
@endDocuBlock AQLEXP_01_explainCreate
|
||||
|
||||
The as you can see, result details are very verbose so we will not shown them in full in the next
|
||||
As you can see, the result details are very verbose so we will not show them in full in the next
|
||||
sections. Instead, lets take a closer look at the results step by step.
|
||||
|
||||
!SUBSUBSECTION Execution nodes
|
||||
|
|
|
|||
|
|
@ -18,11 +18,6 @@ FOR u IN users
|
|||
RETURN u
|
||||
```
|
||||
|
||||
In the above example, all array elements from *users* will be included that have
|
||||
an attribute *active* with value *true* and that have an attribute *age* with a
|
||||
value less than *39* (including *null* ones). All other elements from *users*
|
||||
will be skipped and not be included the result produced by *RETURN*.
|
||||
|
||||
It is allowed to specify multiple *FILTER* statements in a query, and even in
|
||||
the same block. If multiple *FILTER* statements are used, their results will be
|
||||
combined with a logical and, meaning all filter conditions must be true to
|
||||
|
|
@ -35,3 +30,12 @@ FOR u IN users
|
|||
RETURN u
|
||||
```
|
||||
|
||||
In the above example, will be included in the result all array elements from *users* that have
|
||||
an attribute *active* with value *true* and that have an attribute *age* with a
|
||||
value less than *39* (including *null* ones). All other elements from *users*
|
||||
will be skipped and not be included in the result produced by *RETURN*.
|
||||
You may refer to the chapter [Accessing Data from Collections](../Aql/DocumentData.md) for
|
||||
a description of the impact of non-existent or null attributes.
|
||||
|
||||
|
||||
|
||||
|
|
|
|||
|
|
@ -71,6 +71,7 @@
|
|||
* [Limitations](Transactions/Limitations.md)
|
||||
* [AQL](Aql/README.md)
|
||||
* [How to invoke AQL](Aql/Invoke.md)
|
||||
* [AQL with Arangosh](Aql/AqlWithArangosh.md)
|
||||
* [Data modification queries](Aql/DataModification.md)
|
||||
* [AQL Fundamentals](Aql/Fundamentals.md)
|
||||
* [AQL Syntax](Aql/Syntax.md)
|
||||
|
|
|
|||
Loading…
Reference in New Issue