Add SQL/JSON query functions

This introduces the following SQL/JSON functions for querying JSON
data using jsonpath expressions:

JSON_EXISTS(), which can be used to apply a jsonpath expression to a
JSON value to check if it yields any values.

JSON_QUERY(), which can be used to to apply a jsonpath expression to
a JSON value to get a JSON object, an array, or a string.  There are
various options to control whether multi-value result uses array
wrappers and whether the singleton scalar strings are quoted or not.

JSON_VALUE(), which can be used to apply a jsonpath expression to a
JSON value to return a single scalar value, producing an error if it
multiple values are matched.

Both JSON_VALUE() and JSON_QUERY() functions have options for
handling EMPTY and ERROR conditions, which can be used to specify
the behavior when no values are matched and when an error occurs
during jsonpath evaluation, respectively.

Author: Nikita Glukhov <n.gluhov@postgrespro.ru>
Author: Teodor Sigaev <teodor@sigaev.ru>
Author: Oleg Bartunov <obartunov@gmail.com>
Author: Alexander Korotkov <aekorotkov@gmail.com>
Author: Andrew Dunstan <andrew@dunslane.net>
Author: Amit Langote <amitlangote09@gmail.com>
Author: Peter Eisentraut <peter@eisentraut.org>
Author: Jian He <jian.universality@gmail.com>

Reviewers have included (in no particular order):

Andres Freund, Alexander Korotkov, Pavel Stehule, Andrew Alsup,
Erik Rijkers, Zihong Yu, Himanshu Upadhyaya, Daniel Gustafsson,
Justin Pryzby, Álvaro Herrera, Jian He, Anton A. Melnikov,
Nikita Malakhov, Peter Eisentraut, Tomas Vondra

Discussion: https://postgr.es/m/cd0bb935-0158-78a7-08b5-904886deac4b@postgrespro.ru
Discussion: https://postgr.es/m/20220616233130.rparivafipt6doj3@alap3.anarazel.de
Discussion: https://postgr.es/m/abd9b83b-aa66-f230-3d6d-734817f0995d%40postgresql.org
Discussion: https://postgr.es/m/CA+HiwqHROpf9e644D8BRqYvaAPmgBZVup-xKMDPk-nd4EpgzHw@mail.gmail.com
Discussion: https://postgr.es/m/CA+HiwqE4XTdfb1nW=Ojoy_tQSRhYt-q_kb6i5d4xcKyrLC1Nbg@mail.gmail.com

2 files changed, 111 insertions, 0 deletions

diff --git a/src/backend/jit/llvm/llvmjit_expr.c b/src/backend/jit/llvm/llvmjit_expr.c
index 2a7d84f046b..9e0efd26687 100644
--- a/src/backend/jit/llvm/llvmjit_expr.c
+++ b/src/backend/jit/llvm/llvmjit_expr.c
@@ -1930,6 +1930,114 @@ llvm_compile_expr(ExprState *state)
 				LLVMBuildBr(b, opblocks[opno + 1]);
 				break;
 
+			case EEOP_JSONEXPR_PATH:
+				{
+					JsonExprState *jsestate = op->d.jsonexpr.jsestate;
+					LLVMValueRef v_ret;
+
+					/*
+					 * Call ExecEvalJsonExprPath().  It returns the address of
+					 * the step to perform next.
+					 */
+					v_ret = build_EvalXFunc(b, mod, "ExecEvalJsonExprPath",
+											v_state, op, v_econtext);
+
+					/*
+					 * Build a switch to map the return value (v_ret above),
+					 * which is a runtime value of the step address to perform
+					 * next, to either jump_empty, jump_error,
+					 * jump_eval_coercion, or jump_end.
+					 */
+					if (jsestate->jump_empty >= 0 ||
+						jsestate->jump_error >= 0 ||
+						jsestate->jump_eval_coercion >= 0)
+					{
+						LLVMValueRef v_jump_empty;
+						LLVMValueRef v_jump_error;
+						LLVMValueRef v_jump_coercion;
+						LLVMValueRef v_switch;
+						LLVMBasicBlockRef b_done,
+									b_empty,
+									b_error,
+									b_coercion;
+
+						b_empty =
+							l_bb_before_v(opblocks[opno + 1],
+										  "op.%d.jsonexpr_empty", opno);
+						b_error =
+							l_bb_before_v(opblocks[opno + 1],
+										  "op.%d.jsonexpr_error", opno);
+						b_coercion =
+							l_bb_before_v(opblocks[opno + 1],
+										  "op.%d.jsonexpr_coercion", opno);
+						b_done =
+							l_bb_before_v(opblocks[opno + 1],
+										  "op.%d.jsonexpr_done", opno);
+
+						v_switch = LLVMBuildSwitch(b,
+												   v_ret,
+												   b_done,
+												   3);
+						/* Returned jsestate->jump_empty? */
+						if (jsestate->jump_empty >= 0)
+						{
+							v_jump_empty = l_int32_const(lc, jsestate->jump_empty);
+							LLVMAddCase(v_switch, v_jump_empty, b_empty);
+						}
+						/* ON EMPTY code */
+						LLVMPositionBuilderAtEnd(b, b_empty);
+						if (jsestate->jump_empty >= 0)
+							LLVMBuildBr(b, opblocks[jsestate->jump_empty]);
+						else
+							LLVMBuildUnreachable(b);
+
+						/* Returned jsestate->jump_error? */
+						if (jsestate->jump_error >= 0)
+						{
+							v_jump_error = l_int32_const(lc, jsestate->jump_error);
+							LLVMAddCase(v_switch, v_jump_error, b_error);
+						}
+						/* ON ERROR code */
+						LLVMPositionBuilderAtEnd(b, b_error);
+						if (jsestate->jump_error >= 0)
+							LLVMBuildBr(b, opblocks[jsestate->jump_error]);
+						else
+							LLVMBuildUnreachable(b);
+
+						/* Returned jsestate->jump_eval_coercion? */
+						if (jsestate->jump_eval_coercion >= 0)
+						{
+							v_jump_coercion = l_int32_const(lc, jsestate->jump_eval_coercion);
+							LLVMAddCase(v_switch, v_jump_coercion, b_coercion);
+						}
+						/* coercion_expr code */
+						LLVMPositionBuilderAtEnd(b, b_coercion);
+						if (jsestate->jump_eval_coercion >= 0)
+							LLVMBuildBr(b, opblocks[jsestate->jump_eval_coercion]);
+						else
+							LLVMBuildUnreachable(b);
+
+						LLVMPositionBuilderAtEnd(b, b_done);
+					}
+
+					LLVMBuildBr(b, opblocks[jsestate->jump_end]);
+					break;
+				}
+
+			case EEOP_JSONEXPR_COERCION:
+				build_EvalXFunc(b, mod, "ExecEvalJsonCoercion",
+								v_state, op, v_econtext);
+
+				LLVMBuildBr(b, opblocks[opno + 1]);
+				break;
+
+			case EEOP_JSONEXPR_COERCION_FINISH:
+				build_EvalXFunc(b, mod, "ExecEvalJsonCoercionFinish",
+								v_state, op);
+
+				LLVMBuildBr(b, opblocks[opno + 1]);
+				break;
+
 			case EEOP_AGGREF:
 				{
 					LLVMValueRef v_aggno;
diff --git a/src/backend/jit/llvm/llvmjit_types.c b/src/backend/jit/llvm/llvmjit_types.c
index 7d7aeee1f2b..f93c383fd52 100644
--- a/src/backend/jit/llvm/llvmjit_types.c
+++ b/src/backend/jit/llvm/llvmjit_types.c
@@ -173,6 +173,9 @@ void	   *referenced_functions[] =
 	ExecEvalXmlExpr,
 	ExecEvalJsonConstructor,
 	ExecEvalJsonIsPredicate,
+	ExecEvalJsonCoercion,
+	ExecEvalJsonCoercionFinish,
+	ExecEvalJsonExprPath,
 	MakeExpandedObjectReadOnlyInternal,
 	slot_getmissingattrs,
 	slot_getsomeattrs_int,