Revise child-to-root tuple conversion map management.

Store the tuple conversion map to convert a tuple from a child table's
format to the root format in a new ri_ChildToRootMap field in
ResultRelInfo. It is initialized if transition tuple capture for FOR
STATEMENT triggers or INSERT tuple routing on a partitioned table is
needed. Previously, ModifyTable kept the maps in the per-subplan
ModifyTableState->mt_per_subplan_tupconv_maps array, or when tuple
routing was used, in
ResultRelInfo->ri_Partitioninfo->pi_PartitionToRootMap. The new field
replaces both of those.

Now that the child-to-root tuple conversion map is always available in
ResultRelInfo (when needed), remove the TransitionCaptureState.tcs_map
field. The callers of Exec*Trigger() functions no longer need to set or
save it, which is much less confusing and bug-prone. Also, as a future
optimization, this will allow us to delay creating the map for a given
result relation until the relation is actually processed during
execution.

Author: Amit Langote
Discussion: https://www.postgresql.org/message-id/CA%2BHiwqHtCWLdK-LO%3DNEsvOdHx%2B7yv4mE_zYK0i3BH7dXb-wxog%40mail.gmail.com

3 files changed, 8 insertions, 18 deletions

diff --git a/src/include/commands/trigger.h b/src/include/commands/trigger.h
index a40ddf5db52..e38d732ed47 100644
--- a/src/include/commands/trigger.h
+++ b/src/include/commands/trigger.h
@@ -46,7 +46,7 @@ typedef struct TriggerData
  * The state for capturing old and new tuples into transition tables for a
  * single ModifyTable node (or other operation source, e.g. copy.c).
  *
- * This is per-caller to avoid conflicts in setting tcs_map or
+ * This is per-caller to avoid conflicts in setting
  * tcs_original_insert_tuple.  Note, however, that the pointed-to
  * private data may be shared across multiple callers.
  */
@@ -66,14 +66,6 @@ typedef struct TransitionCaptureState
 	bool		tcs_insert_new_table;
 
 	/*
-	 * For UPDATE and DELETE, AfterTriggerSaveEvent may need to convert the
-	 * new and old tuples from a child table's format to the format of the
-	 * relation named in a query so that it is compatible with the transition
-	 * tuplestores.  The caller must store the conversion map here if so.
-	 */
-	TupleConversionMap *tcs_map;
-
-	/*
 	 * For INSERT and COPY, it would be wasteful to convert tuples from child
 	 * format to parent format after they have already been converted in the
 	 * opposite direction during routing.  In that case we bypass conversion
diff --git a/src/include/executor/execPartition.h b/src/include/executor/execPartition.h
index 6d1b7221987..74c39911b2a 100644
--- a/src/include/executor/execPartition.h
+++ b/src/include/executor/execPartition.h
@@ -37,12 +37,6 @@ typedef struct PartitionRoutingInfo
 	TupleConversionMap *pi_RootToPartitionMap;
 
 	/*
-	 * Map for converting tuples in partition format into the root partitioned
-	 * table format, or NULL if no conversion is required.
-	 */
-	TupleConversionMap *pi_PartitionToRootMap;
-
-	/*
 	 * Slot to store tuples in partition format, or NULL when no translation
 	 * is required between root and partition.
 	 */
diff --git a/src/include/nodes/execnodes.h b/src/include/nodes/execnodes.h
index dff34fbc14e..46789cb0070 100644
--- a/src/include/nodes/execnodes.h
+++ b/src/include/nodes/execnodes.h
@@ -486,6 +486,13 @@ typedef struct ResultRelInfo
 	/* info for partition tuple routing (NULL if not set up yet) */
 	struct PartitionRoutingInfo *ri_PartitionInfo;
 
+	/*
+	 * Map to convert child result relation tuples to the format of the table
+	 * actually mentioned in the query (called "root").  Set only if
+	 * transition tuple capture or update partition row movement is active.
+	 */
+	TupleConversionMap *ri_ChildToRootMap;
+
 	/* for use by copy.c when performing multi-inserts */
 	struct CopyMultiInsertBuffer *ri_CopyMultiInsertBuffer;
 } ResultRelInfo;
@@ -1179,9 +1186,6 @@ typedef struct ModifyTableState
 
 	/* controls transition table population for INSERT...ON CONFLICT UPDATE */
 	struct TransitionCaptureState *mt_oc_transition_capture;
-
-	/* Per plan map for tuple conversion from child to root */
-	TupleConversionMap **mt_per_subplan_tupconv_maps;
 } ModifyTableState;
 
 /* ----------------