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PLAN clauses for JSON_TABLE

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These clauses allow the user to specify how data from nested paths are
joined, allowing considerable freedom in shaping the tabular output of
JSON_TABLE.

PLAN DEFAULT allows the user to specify the global strategies when
dealing with sibling or child nested paths. The is often sufficient to
achieve the necessary goal, and is considerably simpler than the full
PLAN clause, which allows the user to specify the strategy to be used
for each named nested path.

Nikita Glukhov

Reviewers have included (in no particular order) Andres Freund, Alexander
Korotkov, Pavel Stehule, Andrew Alsup, Erik Rijkers, Zhihong Yu,
Himanshu Upadhyaya, Daniel Gustafsson, Justin Pryzby.

Discussion: https://postgr.es/m/7e2cb85d-24cf-4abb-30a5-1a33715959bd@postgrespro.ru
This commit is contained in:
Andrew Dunstan
2022-04-05 14:09:04 -04:00
parent e83ebfe6d7
commit fadb48b00e
17 changed files with 1622 additions and 117 deletions
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134
src/backend/utils/adt/jsonpath_exec.c
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@ -175,6 +175,7 @@ struct JsonTableScanState
Datum current;
int ordinal;
bool currentIsNull;
bool outerJoin;
bool errorOnError;
bool advanceNested;
bool reset;
@ -188,6 +189,7 @@ struct JsonTableJoinState
{
JsonTableJoinState *left;
JsonTableJoinState *right;
bool cross;
bool advanceRight;
} join;
JsonTableScanState scan;
@ -3166,6 +3168,7 @@ JsonTableInitScanState(JsonTableContext *cxt, JsonTableScanState *scan,
int i;
scan->parent = parent;
scan->outerJoin = node->outerJoin;
scan->errorOnError = node->errorOnError;
scan->path = DatumGetJsonPathP(node->path->constvalue);
scan->args = args;
@ -3192,6 +3195,7 @@ JsonTableInitPlanState(JsonTableContext *cxt, Node *plan,
JsonTableSibling *join = castNode(JsonTableSibling, plan);
state->is_join = true;
state->u.join.cross = join->cross;
state->u.join.left = JsonTableInitPlanState(cxt, join->larg, parent);
state->u.join.right = JsonTableInitPlanState(cxt, join->rarg, parent);
}
@ -3328,8 +3332,26 @@ JsonTableSetDocument(TableFuncScanState *state, Datum value)
JsonTableResetContextItem(&cxt->root, value);
}
/* Recursively reset scan and its child nodes */
static void
JsonTableRescanRecursive(JsonTableJoinState *state)
{
if (state->is_join)
{
JsonTableRescanRecursive(state->u.join.left);
JsonTableRescanRecursive(state->u.join.right);
state->u.join.advanceRight = false;
}
else
{
JsonTableRescan(&state->u.scan);
if (state->u.scan.nested)
JsonTableRescanRecursive(state->u.scan.nested);
}
}
/*
* Fetch next row from a union joined scan.
* Fetch next row from a cross/union joined scan.
*
* Returns false at the end of a scan, true otherwise.
*/
@ -3339,17 +3361,48 @@ JsonTableNextJoinRow(JsonTableJoinState *state)
if (!state->is_join)
return JsonTableNextRow(&state->u.scan);
if (!state->u.join.advanceRight)
if (state->u.join.advanceRight)
{
/* fetch next outer row */
if (JsonTableNextJoinRow(state->u.join.left))
/* fetch next inner row */
if (JsonTableNextJoinRow(state->u.join.right))
return true;
state->u.join.advanceRight = true; /* next inner row */
/* inner rows are exhausted */
if (state->u.join.cross)
state->u.join.advanceRight = false; /* next outer row */
else
return false; /* end of scan */
}
/* fetch next inner row */
return JsonTableNextJoinRow(state->u.join.right);
while (!state->u.join.advanceRight)
{
/* fetch next outer row */
bool left = JsonTableNextJoinRow(state->u.join.left);
if (state->u.join.cross)
{
if (!left)
return false; /* end of scan */
JsonTableRescanRecursive(state->u.join.right);
if (!JsonTableNextJoinRow(state->u.join.right))
continue; /* next outer row */
state->u.join.advanceRight = true; /* next inner row */
}
else if (!left)
{
if (!JsonTableNextJoinRow(state->u.join.right))
return false; /* end of scan */
state->u.join.advanceRight = true; /* next inner row */
}
break;
}
return true;
}
/* Recursively set 'reset' flag of scan and its child nodes */
@ -3373,16 +3426,13 @@ JsonTableJoinReset(JsonTableJoinState *state)
}
/*
* Fetch next row from a simple scan with outer joined nested subscans.
* Fetch next row from a simple scan with outer/inner joined nested subscans.
*
* Returns false at the end of a scan, true otherwise.
*/
static bool
JsonTableNextRow(JsonTableScanState *scan)
{
JsonbValue *jbv;
MemoryContext oldcxt;
/* reset context item if requested */
if (scan->reset)
{
@ -3394,34 +3444,42 @@ JsonTableNextRow(JsonTableScanState *scan)
if (scan->advanceNested)
{
/* fetch next nested row */
if (JsonTableNextJoinRow(scan->nested))
return true;
scan->advanceNested = false;
}
/* fetch next row */
jbv = JsonValueListNext(&scan->found, &scan->iter);
if (!jbv)
{
scan->current = PointerGetDatum(NULL);
scan->currentIsNull = true;
return false; /* end of scan */
}
/* set current row item */
oldcxt = MemoryContextSwitchTo(scan->mcxt);
scan->current = JsonbPGetDatum(JsonbValueToJsonb(jbv));
scan->currentIsNull = false;
MemoryContextSwitchTo(oldcxt);
scan->ordinal++;
if (scan->nested)
{
JsonTableJoinReset(scan->nested);
scan->advanceNested = JsonTableNextJoinRow(scan->nested);
if (scan->advanceNested)
return true;
}
for (;;)
{
/* fetch next row */
JsonbValue *jbv = JsonValueListNext(&scan->found, &scan->iter);
MemoryContext oldcxt;
if (!jbv)
{
scan->current = PointerGetDatum(NULL);
scan->currentIsNull = true;
return false; /* end of scan */
}
/* set current row item */
oldcxt = MemoryContextSwitchTo(scan->mcxt);
scan->current = JsonbPGetDatum(JsonbValueToJsonb(jbv));
scan->currentIsNull = false;
MemoryContextSwitchTo(oldcxt);
scan->ordinal++;
if (!scan->nested)
break;
JsonTableJoinReset(scan->nested);
scan->advanceNested = JsonTableNextJoinRow(scan->nested);
if (scan->advanceNested || scan->outerJoin)
break;
}
return true;