Add jit provider's version into the pgsql_version

If jit provider is available and initialized, add its version string
into the pgsql_version output. This should help to get more relevant
information in bug reports about JIT.

Author: erthalion

src/backend/jit/jit.c

@@ -189,3 +189,16 @@ InstrJitAgg(JitInstrumentation *dst, JitInstrumentation *add)
 	INSTR_TIME_ADD(dst->optimization_counter, add->optimization_counter);
 	INSTR_TIME_ADD(dst->emission_counter, add->emission_counter);
 }
+
+/*
+ * Return JIT provider's version string for troubleshooting purposes.
+ */
+const char *
+jit_get_version(bool *available)
+{
+	if (provider_init())
+		return provider.get_version(available);
+
+	*available = false;
+	return "";
+}

src/backend/jit/llvm/llvmjit.c

@@ -154,6 +154,7 @@ _PG_jit_provider_init(JitProviderCallbacks *cb)
 	cb->reset_after_error = llvm_reset_after_error;
 	cb->release_context = llvm_release_context;
 	cb->compile_expr = llvm_compile_expr;
+	cb->get_version = llvm_version;
 }
 
 
@@ -1287,3 +1288,19 @@ ResOwnerReleaseJitContext(Datum res)
 	context->resowner = NULL;
 	jit_release_context(&context->base);
 }
+
+const char *
+llvm_version(bool *available)
+{
+#if LLVM_VERSION_MAJOR > 15
+	unsigned int major, minor, patch;
+
+	LLVMGetVersion(&major, &minor, &patch);
+
+	*available = true;
+	return (const char*) psprintf("llvm: %d.%d.%d", major, minor, patch);
+#else
+	*available = false;
+	return "";
+#endif
+}

src/backend/utils/adt/version.c

@@ -15,10 +15,23 @@
 #include "postgres.h"
 
 #include "utils/builtins.h"
+#include "jit/jit.h"
 
 
 Datum
 pgsql_version(PG_FUNCTION_ARGS)
 {
-	PG_RETURN_TEXT_P(cstring_to_text(PG_VERSION_STR));
+	bool jit_available = false;
+	const char *jit_version = jit_get_version(&jit_available);
+
+	/* Add jit provides's version string if available. */
+	if (jit_available)
+	{
+		PG_RETURN_TEXT_P(cstring_to_text(psprintf("%s, %s", PG_VERSION_STR,
+												  jit_version)));
+	}
+	else
+	{
+		PG_RETURN_TEXT_P(cstring_to_text(PG_VERSION_STR));
+	}
 }

src/include/jit/jit.h

@@ -70,12 +70,14 @@ typedef void (*JitProviderResetAfterErrorCB) (void);
 typedef void (*JitProviderReleaseContextCB) (JitContext *context);
 struct ExprState;
 typedef bool (*JitProviderCompileExprCB) (struct ExprState *state);
+typedef const char* (*JitProviderVersion) (bool *available);
 
 struct JitProviderCallbacks
 {
 	JitProviderResetAfterErrorCB reset_after_error;
 	JitProviderReleaseContextCB release_context;
 	JitProviderCompileExprCB compile_expr;
+	JitProviderVersion get_version;
 };
 
 
@@ -102,5 +104,11 @@ extern void jit_release_context(JitContext *context);
 extern bool jit_compile_expr(struct ExprState *state);
 extern void InstrJitAgg(JitInstrumentation *dst, JitInstrumentation *add);
 
+/*
+ * Get the provider's version string. The flag indicating availability is
+ * passed as an argument, and will be set accordingly if it's not possible to
+ * get the version.
+ */
+extern const char *jit_get_version(bool *available);
 
 #endif							/* JIT_H */

src/include/jit/llvmjit.h

@@ -145,6 +145,8 @@ extern LLVMTypeRef LLVMGetFunctionType(LLVMValueRef r);
 extern LLVMOrcObjectLayerRef LLVMOrcCreateRTDyldObjectLinkingLayerWithSafeSectionMemoryManager(LLVMOrcExecutionSessionRef ES);
 #endif
 
+extern const char* llvm_version(bool *available);
+
 #ifdef __cplusplus
 } /* extern "C" */
 #endif