commit 79d0dc78b9f3b0bbc078876417b8f46970308e6e
Author: Jacob Champion <champion.p@gmail.com>
Date:   Thu Jan 4 11:46:06 2024 -0800

    WIP: try to speed up prediction

diff --git a/src/common/jsonapi.c b/src/common/jsonapi.c
index d875d57df7..9149d45a4b 100644
--- a/src/common/jsonapi.c
+++ b/src/common/jsonapi.c
@@ -165,39 +165,47 @@ static char JSON_PROD_MORE_KEY_PAIRS[] = {JSON_NT_MORE_KEY_PAIRS, JSON_NT_KEYPAI
  * Any combination not specified here represents an error.
  */
 
-static char *td_parser_table[JSON_NUM_NONTERMINALS][JSON_NUM_TERMINALS] =
+struct td_entry
+{
+	size_t		len;
+	char	   *prod;
+};
+
+#define TD_ENTRY(PROD) { sizeof(PROD) - 1, (PROD) }
+
+static struct td_entry td_parser_table[JSON_NUM_NONTERMINALS][JSON_NUM_TERMINALS] =
 {
 	/* JSON */
-	[OFS(JSON_NT_JSON)][JSON_TOKEN_STRING] = JSON_PROD_SCALAR_STRING,
-	[OFS(JSON_NT_JSON)][JSON_TOKEN_NUMBER] = JSON_PROD_SCALAR_NUMBER,
-	[OFS(JSON_NT_JSON)][JSON_TOKEN_TRUE] = JSON_PROD_SCALAR_TRUE,
-	[OFS(JSON_NT_JSON)][JSON_TOKEN_FALSE] = JSON_PROD_SCALAR_FALSE,
-	[OFS(JSON_NT_JSON)][JSON_TOKEN_NULL] = JSON_PROD_SCALAR_NULL,
-	[OFS(JSON_NT_JSON)][JSON_TOKEN_ARRAY_START] = JSON_PROD_ARRAY,
-	[OFS(JSON_NT_JSON)][JSON_TOKEN_OBJECT_START] = JSON_PROD_OBJECT,
+	[OFS(JSON_NT_JSON)][JSON_TOKEN_STRING] = TD_ENTRY(JSON_PROD_SCALAR_STRING),
+	[OFS(JSON_NT_JSON)][JSON_TOKEN_NUMBER] = TD_ENTRY(JSON_PROD_SCALAR_NUMBER),
+	[OFS(JSON_NT_JSON)][JSON_TOKEN_TRUE] = TD_ENTRY(JSON_PROD_SCALAR_TRUE),
+	[OFS(JSON_NT_JSON)][JSON_TOKEN_FALSE] = TD_ENTRY(JSON_PROD_SCALAR_FALSE),
+	[OFS(JSON_NT_JSON)][JSON_TOKEN_NULL] = TD_ENTRY(JSON_PROD_SCALAR_NULL),
+	[OFS(JSON_NT_JSON)][JSON_TOKEN_ARRAY_START] = TD_ENTRY(JSON_PROD_ARRAY),
+	[OFS(JSON_NT_JSON)][JSON_TOKEN_OBJECT_START] = TD_ENTRY(JSON_PROD_OBJECT),
 	/* ARRAY_ELEMENTS */
-	[OFS(JSON_NT_ARRAY_ELEMENTS)][JSON_TOKEN_ARRAY_START] = JSON_PROD_ARRAY_ELEMENTS,
-	[OFS(JSON_NT_ARRAY_ELEMENTS)][JSON_TOKEN_OBJECT_START] = JSON_PROD_ARRAY_ELEMENTS,
-	[OFS(JSON_NT_ARRAY_ELEMENTS)][JSON_TOKEN_STRING] = JSON_PROD_ARRAY_ELEMENTS,
-	[OFS(JSON_NT_ARRAY_ELEMENTS)][JSON_TOKEN_NUMBER] = JSON_PROD_ARRAY_ELEMENTS,
-	[OFS(JSON_NT_ARRAY_ELEMENTS)][JSON_TOKEN_TRUE] = JSON_PROD_ARRAY_ELEMENTS,
-	[OFS(JSON_NT_ARRAY_ELEMENTS)][JSON_TOKEN_FALSE] = JSON_PROD_ARRAY_ELEMENTS,
-	[OFS(JSON_NT_ARRAY_ELEMENTS)][JSON_TOKEN_NULL] = JSON_PROD_ARRAY_ELEMENTS,
-	[OFS(JSON_NT_ARRAY_ELEMENTS)][JSON_TOKEN_ARRAY_END] = JSON_PROD_EPSILON,
+	[OFS(JSON_NT_ARRAY_ELEMENTS)][JSON_TOKEN_ARRAY_START] = TD_ENTRY(JSON_PROD_ARRAY_ELEMENTS),
+	[OFS(JSON_NT_ARRAY_ELEMENTS)][JSON_TOKEN_OBJECT_START] = TD_ENTRY(JSON_PROD_ARRAY_ELEMENTS),
+	[OFS(JSON_NT_ARRAY_ELEMENTS)][JSON_TOKEN_STRING] = TD_ENTRY(JSON_PROD_ARRAY_ELEMENTS),
+	[OFS(JSON_NT_ARRAY_ELEMENTS)][JSON_TOKEN_NUMBER] = TD_ENTRY(JSON_PROD_ARRAY_ELEMENTS),
+	[OFS(JSON_NT_ARRAY_ELEMENTS)][JSON_TOKEN_TRUE] = TD_ENTRY(JSON_PROD_ARRAY_ELEMENTS),
+	[OFS(JSON_NT_ARRAY_ELEMENTS)][JSON_TOKEN_FALSE] = TD_ENTRY(JSON_PROD_ARRAY_ELEMENTS),
+	[OFS(JSON_NT_ARRAY_ELEMENTS)][JSON_TOKEN_NULL] = TD_ENTRY(JSON_PROD_ARRAY_ELEMENTS),
+	[OFS(JSON_NT_ARRAY_ELEMENTS)][JSON_TOKEN_ARRAY_END] = TD_ENTRY(JSON_PROD_EPSILON),
 	/* MORE_ARRAY_ELEMENTS */
-	[OFS(JSON_NT_MORE_ARRAY_ELEMENTS)][JSON_TOKEN_COMMA] = JSON_PROD_MORE_ARRAY_ELEMENTS,
-	[OFS(JSON_NT_MORE_ARRAY_ELEMENTS)][JSON_TOKEN_ARRAY_END] = JSON_PROD_EPSILON,
+	[OFS(JSON_NT_MORE_ARRAY_ELEMENTS)][JSON_TOKEN_COMMA] = TD_ENTRY(JSON_PROD_MORE_ARRAY_ELEMENTS),
+	[OFS(JSON_NT_MORE_ARRAY_ELEMENTS)][JSON_TOKEN_ARRAY_END] = TD_ENTRY(JSON_PROD_EPSILON),
 
 	/*
 	 * KEYPAIR - could expand but it's clearer not to.
 	 */
-	[OFS(JSON_NT_KEYPAIR)][JSON_TOKEN_STRING] = JSON_PROD_KEYPAIR,
+	[OFS(JSON_NT_KEYPAIR)][JSON_TOKEN_STRING] = TD_ENTRY(JSON_PROD_KEYPAIR),
 	/* KEY_PAIRS */
-	[OFS(JSON_NT_KEY_PAIRS)][JSON_TOKEN_STRING] = JSON_PROD_KEY_PAIRS,
-	[OFS(JSON_NT_KEY_PAIRS)][JSON_TOKEN_OBJECT_END] = JSON_PROD_EPSILON,
+	[OFS(JSON_NT_KEY_PAIRS)][JSON_TOKEN_STRING] = TD_ENTRY(JSON_PROD_KEY_PAIRS),
+	[OFS(JSON_NT_KEY_PAIRS)][JSON_TOKEN_OBJECT_END] = TD_ENTRY(JSON_PROD_EPSILON),
 	/* MORE_KEY_PAIRS */
-	[OFS(JSON_NT_MORE_KEY_PAIRS)][JSON_TOKEN_COMMA] = JSON_PROD_MORE_KEY_PAIRS,
-	[OFS(JSON_NT_MORE_KEY_PAIRS)][JSON_TOKEN_OBJECT_END] = JSON_PROD_EPSILON,
+	[OFS(JSON_NT_MORE_KEY_PAIRS)][JSON_TOKEN_COMMA] = TD_ENTRY(JSON_PROD_MORE_KEY_PAIRS),
+	[OFS(JSON_NT_MORE_KEY_PAIRS)][JSON_TOKEN_OBJECT_END] = TD_ENTRY(JSON_PROD_EPSILON),
 };
 
 /* the GOAL production. Not stored in the table, but will be the initial contents of the prediction stack */
@@ -419,11 +427,10 @@ dec_lex_level(JsonLexContext *lex)
 }
 
 static inline void
-push_prediction(JsonParserStack *pstack, char *prod)
+push_prediction(JsonParserStack *pstack, struct td_entry entry)
 {
-	int len = strlen(prod);
-	memcpy(pstack->prediction + pstack->pred_index, prod, len);
-	pstack->pred_index += len;
+	memcpy(pstack->prediction + pstack->pred_index, entry.prod, entry.len);
+	pstack->pred_index += entry.len;
 }
 
 static inline char
@@ -651,12 +658,15 @@ pg_parse_json_incremental(JsonLexContext *lex,
 	/* use prediction stack for incremental parsing */
 
 	if (!have_prediction(pstack))
-		push_prediction(pstack, JSON_PROD_GOAL);
+	{
+		struct td_entry goal = TD_ENTRY(JSON_PROD_GOAL);
+		push_prediction(pstack, goal);
+	}
 
 	while (have_prediction(pstack))
 	{
 		char		top = pop_prediction(pstack);
-		char	   *prod;
+		struct td_entry entry;
 
 		/*
 		 * these first two branches are the guts of the Table Driven
@@ -676,14 +686,14 @@ pg_parse_json_incremental(JsonLexContext *lex,
 				tok = lex_peek(lex);
 			}
 		}
-		else if (IS_NT(top) && (prod = td_parser_table[OFS(top)][tok]) != NULL)
+		else if (IS_NT(top) && (entry = td_parser_table[OFS(top)][tok]).prod != NULL)
 		{
 			/*
 			 * the token is in the director set for a production of the
 			 * non-terminal at the top of the stack, so push the reversed
 			 * RHS of the production onto the stack.
 			 */
-			push_prediction(pstack, prod);
+			push_prediction(pstack, entry);
 		}
 		else if (IS_SEM(top))
 		{