HFreeQuery (Function)

When to use HFreeQuery?
This function can be used when no other process will be using the result coming from a query. We recommend that you use this function on the queries that return an important number of lines (tens of thousands) in order to free the memory space.

Versions 17 and later

This function is now available for Java applications.

This function is now available for Android applications.

New in version 17

This function is now available for Java applications.

This function is now available for Android applications.

This function is now available for Java applications.

This function is now available for Android applications.

Versions 18 and later

This function is now available in Android widget mode.

This function is now available in Windows Store apps mode.

This function is now available for iPhone/iPad applications.

New in version 18

This function is now available in Android widget mode.

This function is now available in Windows Store apps mode.

This function is now available for iPhone/iPad applications.

This function is now available in Android widget mode.

This function is now available in Windows Store apps mode.

This function is now available for iPhone/iPad applications.

Versions 21 and later

This function is now available in Universal Windows 10 App mode.

New in version 21

This function is now available in Universal Windows 10 App mode.

Remark: From version 19, HFSQL is the new name of HyperFileSQL.

Example

// Initializes the query
IF HExecuteQuery(MyQuery) = False THEN
Error("Error while initializing the query" + CR + HErrorInfo())
RETURN
END

// Read the first record of the query
HReadFirst(MyQuery)
WHILE NOT HOut()
// Process on the query record
...
// Read the next record
HReadNext()
END
HFreeQuery(MyQuery)

Syntax

<Result> = HFreeQuery([<Query>])

<Result>: Boolean

True if the operation was performed,
False if a problem occurs. HError is used to identify the error.

<Query>: Optional character string

Name of a query or a data source associated with a query (for freeing resources after the call to HExecuteQuery or HExecuteSQLQuery).
If this parameter is not specified, corresponds to the last data file used.

Remarks

Conditions for using HFreeQuery

This function must be used ONLY when the query is not required anymore!

In the following example, HFreeQuery is used too soon: the table will be completely wrong. Indeed, BuildBrowsingTable (used to populate the Table control) is run in background task in a parallel process. Therefore, HFreeQuery will operate before the Table control is entirely filled, making this control unusable.

HExecuteSQLQuery("test", "select * from customer")
BuildBrowsingTable(TABLE_Table1, "test")
HFreeQuery("test")

Remark: The problem can also occur with a "data source" variable. A "data source" variable declared locally in a process (button click, procedure, method, etc.) ONLY exists during the execution of this code. For this reason, a "warning" is displayed when you are using this type of data source: "the data source will be destroyed at the end of this code".

Component: wd270hf.dll