orhankislal commented on a change in pull request #476: DL: Avoid constant
folding of weights in GPDB6 plan
URL: https://github.com/apache/madlib/pull/476#discussion_r374853305
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File path: src/ports/postgres/modules/deep_learning/madlib_keras.py_in
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@@ -168,6 +168,23 @@ def fit(schema_madlib, source_table, model,
model_arch_table,
FROM {source_table}
""".format(**locals()), ["bytea", "boolean"])
+ # For >=GPDB6, previously, when the fit_step UDA was called with the
+ # initial weights value passed in, the query plan for it would
+ # create custom plans with weights embedded in the plan itself.
+ # This meant that the query plan size would also include the size
+ # of these weights, bloating it up to hit the 1GB limit when dispatching
+ # the query plan to segments, leading to OOM for large weights.
+ # In GPDB, for PREPARE plans, there is a threshold of 5 attempts to create
+ # custom plans(constant folding the passed in params) for execution and
then
+ # it uses a generic plan(not constant folding the passed in params) for all
+ # the subsequent executions.
+ # Therefore, to avoid GPDB6 from creating custom plans when passing in
+ # weights, the UDA query is executed passing in DUMMY weights for 5
+ # time, prior to calling it with the actual weights.
+ if not is_platform_pg() and not is_platform_gp6():
Review comment:
The comment and the code do not match. Comment implies we want to run this
loop for gpdb 6 but the code has `not is_platform_gp6()`
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