add AQL limits

3.7/aql/fundamentals-limits.md

@@ -0,0 +1,21 @@
+---
+layout: default
+description: Known limitations that apply in AQL queries
+---
+Known limitations for AQL queries
+=================================
+
+The following limitations are known for AQL queries:
+
+- An AQL query cannot use more than _1000_ result registers. One
+ result register is needed for every named query variable and for 
+ internal/anonymous query variables.
+- An AQL query cannot use more than _2048_ collections/shards.
+- It is not possible to use a collection in a read operation after
+ it was used for a write operation in the same AQL query.
+- In the cluster, all vertex collections and collection that are accessed
+ dynamically via the `DOCUMENT` AQL function must be stated in the 
+ query's initial `WITH` statement.
+- Subqueries that are used inside expressions are pulled out of these
+ expressions and executed beforehand. That means that subqueries do not
+ participate in lazy evaluation of operands.

3.7/aql/fundamentals-query-errors.md

@@ -1,6 +1,6 @@
 ---
 layout: default
-description: Issuing an invalid query to the server will result in a parse error if the queryis syntactically invalid
+description: Issuing an invalid query to the server will result in a parse error if the query is syntactically invalid
 ---
 Errors
 ======
@@ -16,9 +16,9 @@ execution will again be aborted and an appropriate error message will be
 returned.
 
 Under some circumstances, executing a query may also produce run-time errors 
-that cannot be predicted from inspecting the query text alone. This is because
-queries may use data from collections that may also be inhomogeneous. Some
-examples that will cause run-time errors are:
+or warnings that cannot be predicted from inspecting the query text alone. 
+This is because queries may use data from collections that may also be inhomogeneous. 
+Some examples that will cause run-time errors or warnings are:
 
 - Division by zero: Will be triggered when an attempt is made to use the value
  *0* as the divisor in an arithmetic division or modulus operation
@@ -33,4 +33,3 @@ examples that will cause run-time errors are:
 
 Please refer to the [Arango Errors](../appendix-error-codes.html) page
 for a list of error codes and meanings.
-

3.7/aql/fundamentals.md

@@ -1,6 +1,6 @@
 ---
 layout: default
-description: Learn more about optimizing your queries by going through thePerformance Course
+description: Learn more about optimizing your queries by going through the Performance Course
 ---
 AQL Fundamentals
 ================
@@ -13,3 +13,4 @@ AQL Fundamentals
 * [Accessing Data from Collections](fundamentals-document-data.html): describes the impact of non-existent or null attributes for selection queries. 
 * [Query Results](fundamentals-query-results.html): the result of an AQL query is an array of values. 
 * [Query Errors](fundamentals-query-errors.html): errors may arise from the AQL parsing or execution. 
+* [Limits](fundamentals-limits.html): known limitations for AQL queries.

3.8/aql/fundamentals-limits.md

@@ -0,0 +1,21 @@
+---
+layout: default
+description: Known limitations that apply in AQL queries
+---
+Known limitations for AQL queries
+=================================
+
+The following limitations are known for AQL queries:
+
+- An AQL query cannot use more than _1000_ result registers. One
+ result register is needed for every named query variable and for 
+ internal/anonymous query variables.
+- An AQL query cannot use more than _2048_ collections/shards.
+- It is not possible to use a collection in a read operation after
+ it was used for a write operation in the same AQL query.
+- In the cluster, all vertex collections and collection that are accessed
+ dynamically via the `DOCUMENT` AQL function must be stated in the 
+ query's initial `WITH` statement.
+- Subqueries that are used inside expressions are pulled out of these
+ expressions and executed beforehand. That means that subqueries do not
+ participate in lazy evaluation of operands.

3.8/aql/fundamentals-query-errors.md

@@ -1,6 +1,6 @@
 ---
 layout: default
-description: Issuing an invalid query to the server will result in a parse error if the queryis syntactically invalid
+description: Issuing an invalid query to the server will result in a parse error if the query is syntactically invalid
 ---
 Errors
 ======
@@ -16,9 +16,9 @@ execution will again be aborted and an appropriate error message will be
 returned.
 
 Under some circumstances, executing a query may also produce run-time errors 
-that cannot be predicted from inspecting the query text alone. This is because
-queries may use data from collections that may also be inhomogeneous. Some
-examples that will cause run-time errors are:
+or warnings that cannot be predicted from inspecting the query text alone. 
+This is because queries may use data from collections that may also be inhomogeneous. 
+Some examples that will cause run-time errors or warnings are:
 
 - Division by zero: Will be triggered when an attempt is made to use the value
  *0* as the divisor in an arithmetic division or modulus operation
@@ -33,4 +33,3 @@ examples that will cause run-time errors are:
 
 Please refer to the [Arango Errors](../appendix-error-codes.html) page
 for a list of error codes and meanings.
-

3.8/aql/fundamentals.md

@@ -13,3 +13,4 @@ AQL Fundamentals
 * [Accessing Data from Collections](fundamentals-document-data.html): describes the impact of non-existent or null attributes for selection queries. 
 * [Query Results](fundamentals-query-results.html): the result of an AQL query is an array of values. 
 * [Query Errors](fundamentals-query-errors.html): errors may arise from the AQL parsing or execution. 
+* [Limits](fundamentals-limits.html): known limitations for AQL queries.