Undo double-quoting of index names in non-text EXPLAIN output formats.

tglsfdc · tglsfdc · commit d3d8755180b6 · 2020-06-22T11:46:41.000-04:00
explain_get_index_name() applied quote_identifier() to the index name. This is fine for text output, but the non-text output formats all have their own quoting conventions and would much rather start from the actual index name. For example in JSON you'd get something like "Index Name": "\"My Index\"", which is surely not desirable, especially when the same does not happen for table names. Hence, move the responsibility for applying quoting out to the callers, where it can go into already-existing special code paths for text format. This changes the API spec for users of explain_get_index_name_hook: before, they were supposed to apply quote_identifier() if necessary, now they should not. Research suggests that the only publicly available user of the hook is hypopg, and it actually forgot to apply quoting anyway, so it's fine. (In any case, there's no behavioral change for the output of a hook as seen in non-text EXPLAIN formats, so this won't break any case that programs should be relying on.) Digging in the commit logs, it appears that quoting was included in explain_get_index_name's duties when commit 604ffd2 invented it; and that was fine at the time because we only had text output format. This should have been rethought when non-text formats were invented, but it wasn't. This is a fairly clear bug for users of non-text EXPLAIN formats, so back-patch to all supported branches. Per bug #16502 from Maciek Sakrejda. Patch by me (based on investigation by Euler Taveira); thanks to Julien Rouhaud for review. Discussion: https://postgr.es/m/16502-57bd1c9f913ed1d1@postgresql.org
diff --git a/src/backend/commands/explain.c b/src/backend/commands/explain.c
@@ -1383,7 +1383,8 @@ ExplainNode(PlanState *planstate, List *ancestors,
 				explain_get_index_name(bitmapindexscan->indexid);
 
 				if (es->format == EXPLAIN_FORMAT_TEXT)
-					appendStringInfo(es->str, " on %s", indexname);
+					appendStringInfo(es->str, " on %s",
+									 quote_identifier(indexname));
 				else
 					ExplainPropertyText("Index Name", indexname, es);
 			}
@@ -2839,6 +2840,10 @@ show_eval_params(Bitmapset *bms_params, ExplainState *es)
  *
  * We allow plugins to get control here so that plans involving hypothetical
  * indexes can be explained.
+ *
+ * Note: names returned by this function should be "raw"; the caller will
+ * apply quoting if needed.  Formerly the convention was to do quoting here,
+ * but we don't want that in non-text output formats.
  */
 static const char *
 explain_get_index_name(Oid indexId)
@@ -2851,11 +2856,10 @@ explain_get_index_name(Oid indexId)
 		result = NULL;
 	if (result == NULL)
 	{
-		/* default behavior: look in the catalogs and quote it */
+		/* default behavior: look it up in the catalogs */
 		result = get_rel_name(indexId);
 		if (result == NULL)
 			elog(ERROR, "cache lookup failed for index %u", indexId);
-		result = quote_identifier(result);
 	}
 	return result;
 }
@@ -2997,7 +3001,7 @@ ExplainIndexScanDetails(Oid indexid, ScanDirection indexorderdir,
 	{
 		if (ScanDirectionIsBackward(indexorderdir))
 			appendStringInfoString(es->str, " Backward");
-		appendStringInfo(es->str, " using %s", indexname);
+		appendStringInfo(es->str, " using %s", quote_identifier(indexname));
 	}
 	else
 	{

Original file line number	Diff line number	Diff line change
`@@ -1383,7 +1383,8 @@ ExplainNode(PlanState planstate, List ancestors,`
`1383`	`1383`	`explain_get_index_name(bitmapindexscan->indexid);`
`1384`	`1384`
`1385`	`1385`	`if (es->format == EXPLAIN_FORMAT_TEXT)`
`1386`		`- appendStringInfo(es->str, " on %s", indexname);`
	`1386`	`+ appendStringInfo(es->str, " on %s",`
	`1387`	`+ quote_identifier(indexname));`
`1387`	`1388`	`else`
`1388`	`1389`	`ExplainPropertyText("Index Name", indexname, es);`
`1389`	`1390`	`}`
`@@ -2839,6 +2840,10 @@ show_eval_params(Bitmapset bms_params, ExplainState es)`
`2839`	`2840`	`*`
`2840`	`2841`	`* We allow plugins to get control here so that plans involving hypothetical`
`2841`	`2842`	`* indexes can be explained.`
	`2843`	`+ *`
	`2844`	`+ * Note: names returned by this function should be "raw"; the caller will`
	`2845`	`+ * apply quoting if needed. Formerly the convention was to do quoting here,`
	`2846`	`+ * but we don't want that in non-text output formats.`
`2842`	`2847`	`*/`
`2843`	`2848`	`static const char *`
`2844`	`2849`	`explain_get_index_name(Oid indexId)`
`@@ -2851,11 +2856,10 @@ explain_get_index_name(Oid indexId)`
`2851`	`2856`	`result = NULL;`
`2852`	`2857`	`if (result == NULL)`
`2853`	`2858`	`{`
`2854`		`- /* default behavior: look in the catalogs and quote it */`
	`2859`	`+ /* default behavior: look it up in the catalogs */`
`2855`	`2860`	`result = get_rel_name(indexId);`
`2856`	`2861`	`if (result == NULL)`
`2857`	`2862`	`elog(ERROR, "cache lookup failed for index %u", indexId);`
`2858`		`- result = quote_identifier(result);`
`2859`	`2863`	`}`
`2860`	`2864`	`return result;`
`2861`	`2865`	`}`
`@@ -2997,7 +3001,7 @@ ExplainIndexScanDetails(Oid indexid, ScanDirection indexorderdir,`
`2997`	`3001`	`{`
`2998`	`3002`	`if (ScanDirectionIsBackward(indexorderdir))`
`2999`	`3003`	`appendStringInfoString(es->str, " Backward");`
`3000`		`- appendStringInfo(es->str, " using %s", indexname);`
	`3004`	`+ appendStringInfo(es->str, " using %s", quote_identifier(indexname));`
`3001`	`3005`	`}`
`3002`	`3006`	`else`
`3003`	`3007`	`{`