STATEMENT PLACEHOLDERS

ANALYSIS:
=========
Executing a prepared statement to do a multi row insertion
with large number of placeholders consumes excessive
memory.

With binlog enabled, the execution takes a long time too.
To write a statement to binlog, the query string is
prepared during the execution. The query string preparation
in this scenario involves many string append calls to
expand heap allocated memory and memcpy. Hence a delay is
observed during the statement execution.

FIX:
====
A reasonable size of memory is reserved for the query
string. Memory of size "original statement string size + 32
times the number of parameters" is reserved to avoid
reallocations during string appends in common use cases.

The String class enforces a limit of 4 GigaBytes for
strings. This can overflow in 64-bit platforms. A check has
been added for 64-bit platforms to handle the overflow. It
is the responsibility of the caller to ensure that the
memory buffer required to hold the string doesn't exceed
4GB. An error is reported if it exceeds 4GB.

A test case was not written for this issue due to
enviromental limitations.

Note:
This patch includes a backport of patch for Bug#27699248.